Surgical treatments

1. Surgical treatment

1.3. PICO table

For full details, see the review protocol in appendix A.

Table 1

PICO characteristics of review question.

1.4. Clinical evidence

1.4.1. Included studies

Sixty-three RCTs were included in the review;^{4, 10, 11, 22, 32, 35, 39, 50, 51, 53, 66, 68, 71, 72, 80, 88, 91, 94, 98, 99, 105, 112, 113, 115, 128, 129, 131, 132, 140, 141, 143, 148, 150, 152, 157, 164, 169, 173, 174, 178, 179, 183, 184, 186–189, 193, 196, 197, 203, 205, 208, 219, 222, 224–227, 237, 241, 244–246}. Twenty-seven studies^{50, 88, 91, 94, 98, 99, 128, 131, 132, 141, 148, 152, 158, 164, 169, 173, 174, 179, 187, 189, 196, 197, 203, 219, 227, 244, 245} compared SWL versus URS, 7 studies^{11, 35, 51, 128, 129, 226, 241} compared SWL versus PCNL, 15 studies^{22, 32, 53, 71, 80, 115, 128, 140, 143, 178, 183, 184, 222, 225, 237} compared URS versus PCNL, and 4 studies^{120, 196, 241, 246} compared surgical (URS, SWL or PCNL) versus non-surgical/conservative treatment. Fourteen studies^{4, 10, 39, 66, 68, 72, 105, 113, 150, 186, 188, 193, 205, 224} looked at within surgery comparisons, including tubeless versus conventional PCNL, mini versus standard PCNL and supine versus prone PCNL.

As per the protocol, for strata where there was no RCT evidence for the children and young people population, the search was widened to include cohort studies. Three studies relevant to the protocol were identified.^{20, 194, 242}

These are summarised in Table 2 below. Evidence from these studies is summarised in the clinical evidence summary below (Table 3).

See also the study selection flow chart in appendix C, study evidence tables in appendix D, forest plots in appendix E and GRADE tables in appendix H.

1.4.2. Excluded studies

See the excluded studies list in appendix I.

1.4.3. Heterogeneity

For the comparison of SWL versus URS in ureteric stones <10mm in adults, there was substantial heterogeneity between the studies when they were meta-analysed for the outcomes of stone-free state, retreatment rate and ancillary procedures. For the comparison of SWL versus URS in ureteric stones 10-20mm, there was heterogeneity between the studies for the outcomes of stone-free state, length of hospital stay, pain, major adverse events and minor adverse events. For the comparison of URS versus PCNL in ureteric stones 10-20mm, there was heterogeneity between the studies for the outcomes of stone-free state, ancillary procedures, length of stay and minor adverse events. For the comparison of SWL versus URS in renal stones <10mm, there was heterogeneity between the studies for the outcome of retreatment rate. For the comparison of surgery versus non-surgical treatment in renal stones <10mm, there was substantial heterogeneity between the studies for the outcome of stone-free state. For the comparison of SWL versus URS in renal stones 10-20mm, there was heterogeneity between the studies for the outcomes of stone-free state, ancillary procedures, length of hospital stay and pain. For the comparison of SWL versus PCNL in renal stones 10-20mm, there was heterogeneity between the studies for the outcome of stone-free state. For the comparison of URS versus PCNL in renal stones 10-20mm, there was substantial heterogeneity between the studies for the outcome of length of stay and pain. For the comparison of URS versus PCNL in renal stones >20mm, there was substantial heterogeneity between the studies for the outcome of stone-free state, length of stay and pain. For the comparison of tubeless versus conventional PCNL in renal stones >20mm, there was heterogeneity between the studies for the outcome of length of stay. For the comparison of supine versus prone PCNL in renal stones >20mm, there was heterogeneity between the studies for the outcome of length of stay. Where pre-specified subgroup analyses (see Appendix A:) were either unable to be performed, or did not explain the heterogeneity, a random effects meta-analysis was applied to these outcomes, and the evidence was downgraded for inconsistency in GRADE.

1.4.4. Summary of clinical studies included in the evidence review

1.4.4.1. Between surgery comparisons

Table 2

Summary of studies included in the evidence review.

1.4.4.2. Within surgery comparisons

Table 3

Summary of studies included in the evidence review.

See appendix D for full evidence tables.

1.4.5. In Quality assessment of clinical studies included in the evidence review

1.4.5.1. Between surgery comparisons

1.4.5.1.1. Adult, ureteric, <10mm

Table 3

Clinical evidence summary: SWL versus URS.

Table 4

Clinical evidence summary: surgery (URS, SWL or PCNL) versus non-surgical treatment.

1.4.5.1.2. Adult, ureteric, 10-20mm

Table 5

Clinical evidence summary: SWL versus URS.

Table 6

Clinical evidence table: URS versus PCNL.

1.4.5.1.3. Children, ureteric, <10mm

Table 7

Clinical evidence table: SWL versus URS.

1.4.5.1.4. Adult, renal, <10mm

Table 8

Clinical evidence summary: SWL versus URS.

Table 9

Clinical evidence summary: SWL versus PCNL.

Table 10

Clinical evidence summary: surgery (URS, SWL or PCNL) versus non-surgical treatment.

1.4.5.1.5. Adult, renal, 10-20mm

Table 11

Clinical evidence summary: SWL versus URS.

Table 12

Clinical evidence summary: SWL versus PCNL.

Table 13

Clinical evidence summary: URS versus PCNL.

Table 14

Clinical evidence summary: surgery (URS, SWL or PCNL) versus non-surgical treatment.

1.4.5.1.6. Adult, renal, >20mm

Table 15

Clinical evidence summary: SWL versus PCNL.

Table 16

Clinical evidence summary: URS versus PCNL.

1.4.5.1.7. Children, renal, 10-20mm

Table 17

Clinical evidence summary: SWL versus URS.

Table 18

Clinical evidence summary: SWL versus PCNL.

Table 19

Clinical evidence summary: URS versus PCNL (non-randomised studies).

1.4.5.1.8. Children, renal, >20mm

Table 20

Clinical evidence summary: URS versus PCNL.

Table 21

Clinical evidence summary: SWL versus PCNL (non-randomised studies).

1.4.5.2. Within surgery comparisons

1.4.5.2.1. Adult, renal, 10-20mm

Table 22

Clinical evidence summary: PCNL: Tubeless versus standard.

1.4.5.2.2. Adult, renal, >20mm

Table 23

Clinical evidence summary: PCNL: Tubeless versus standard.

Table 24

Clinical evidence summary: PCNL: Supine versus prone position.

Table 25

Clinical evidence summary: PCNL: Mini versus standard.

1.4.5.2.3. Children, renal, >20mm

Table 26

Clinical evidence summary: PCNL: Tubeless versus standard.

See appendix F for full GRADE tables.

1.5. Economic evidence

1.5.1. Included studies

No relevant health economic studies were identified.

1.5.2. Excluded studies

Five economic studies relating to this review question were identified but were excluded due to methodological limitations.^{17, 38, 52, 126, 191}. These are listed in appendix I, with reasons for exclusion given.

See also the health economic study selection flow chart in appendix G.

1.5.3. Summary of studies included in the economic evidence review

Table 27

Health economic evidence profile: URS versus SWL, in adults with ureteric stones <10mm.

1.5.4. Health economic model

Three subgroups were identified from the clinical evidence review comparing surgical interventions for people with renal stones, where the committee felt there is the most uncertainty in practice regarding choice of technique, and where the more expensive procedure was more effective. The subgroups are:

• Ureteric stones in adults <10mm: ureteroscopy (URS) versus shockwave lithotripsy (SWL)
• Renal stones in adults <10mm: URS versus SWL
• Renal stones in adults 10-20mm: percutaneous nephrolithotomy (PCNL), versus URS, and SWL

A cost analysis was undertaken for the Ureteric stones in adults <10mm group, and more informal costing was undertaken for the remaining two groups (see section 1.5.6 for a summary of this).

Ureteric stones <10mm: URS vs SWL

Methods

A cost analysis was undertaken to compare the total cost of a strategy that began with URS versus a strategy that began with SWL, for ureteric stones <10mm (for full methods see Appendix 1). URS is a more expensive procedure than SWL. However, the clinical evidence review found that URS was associated with greater success in terms of people being stone-free and, presumably as a result, less retreatment and ancillary procedures. The main consequence of the initial procedure having lower effectiveness is a higher rate of downstream procedures (either a repeat of the initial procedure or a different procedure). This will increase the intervention cost, and therefore to appropriately compare the cost difference between interventions it is important to take this into account. In addition, other outcomes may also vary such as adverse events, and this could also impact overall costs.

Clinical review data was used for the probabilities of retreatment, ancillary procedures, readmission, and major and minor adverse events. Because of concerns about heterogeneity in the data, as well as differences in how stone free outcomes are being reported, and what it is possible to infer about the treatment pathway, multiple scenarios have been undertaken which are informed by different data and with differing assumptions:

1. Cost comparison using only resource use reported in all trials. Assuming that this is the resource use required for everyone to be stone free.
2. Cost comparison using only studies where everyone was stone free at the end of follow up and that also report initial stone free success.
3. Cost comparison using only studies that report more detail on the success of multiple lines of treatment.

Although all scenarios are cost comparisons in the base case, some scenarios have QALY threshold or exploratory QALY work to infer the likelihood of the most expensive intervention being cost effective. More details about each scenario are provided below.

Scenario 1 has the advantage of using all the available clinical data (7 studies), with the assumption that costing up all the resource use will lead to everyone being stone free. This assumption means that this is the resource use difference needed for equivalent outcomes. Limitations of this scenario include that there may still be some difference in outcomes beyond the follow up of the trials, as not everyone was stone free at the end of all the trials. Therefore, if more resources are needed in the SWL arm for everyone to be stone free, then resource use may be being underestimated, in which case the incremental cost might be biasing against URS. This scenario does not have any exploratory QALY work because an average length of follow up would be needed for this, and the studies had different timeframes (ranging from 2 weeks to 3 months).

Scenario 2 uses only 3 studies to inform resource use of retreatments and ancillary procedures. These are studies where everyone is stone free at the end, and also where initial stone free rates are reported. The advantage of using studies where everyone is stone free at the end is that the assumption made in scenario 1 can now be taken as fact, as these are the resources that would be needed for equivalent (100%) effectiveness of the two strategies. Additionally, using studies where initial stone free rates are reported means that we have information about the initial part of the pathway. The difference in initial effectiveness between the two interventions leads to a difference in the number of people who are initially stone free, and therefore a difference in quality of life. Using this logic to infer that the incremental initial effectiveness would be the population contributing to the QALY gain between the interventions, allowing some exploratory QALY work looking at the QALY or quality of life differences required for the most expensive intervention to be cost effective. Disadvantages of this scenario are that it is using only 3 studies to inform inputs. Sensitivity analysis varying the initial effectiveness of SWL down to 40% will also be undertaken, and alongside this the QALY exploratory work for each effectiveness level explored will allow interpretation of whether quality of life gains needed to make URS cost effective are more feasible if SWL is less effective.

Scenario 3 uses only 1 study to inform the resource use inputs on retreatments and ancillary procedures. This study has the benefit of breaking down the number of people that had different lines of treatment, in which case a person could have more than one procedure. This is more detailed than other studies. It also has the advantage of reporting effectiveness that is more reflective of UK practice, which the committee felt was a disadvantage in the clinical review for surgery, as the success of SWL did not reflect the UK experience. Not everyone was stone free at the end of the trial, so the same assumption as scenario 1 is made, whereby this is the resource use needed to get everyone stone free. Disadvantages include that inputs are based only on a single study. This study is also from 1999, so it may be that experience has improved over time for certain techniques such as URS, or technology of SWL machines could have changed. Additionally, not everyone was stone free at the end of the trial, which means that we may be underestimating the resource use associated with SWL, as that is the less effective intervention, and therefore biasing against URS. To combat this, a sensitivity analysis is undertaken adding a fourth line of treatment and assuming that this would successfully lead to everyone being stone free. Some exploratory QALY work is also undertaken in this scenario (through a hypothetical cost utility analysis). Based on some assumptions about when, in the trial, the different lines of treatment would have taken place, and what the utility is with and without a stone, meant an ICER could be calculated. Also the threshold could be identified of what the utility of a non-stone free person would need to be to make URS cost effective.

Common to all scenarios are assumptions about the number of initial sessions of SWL being a single session and retreatment being one additional session, the types of procedures that are ancillary procedures, the proportion requiring stents, and follow up resource use. Unit costs were from NHS reference costs 2016/17.

Sensitivity analyses common to all scenarios include varying initial effectiveness of SWL, varying SWL costs, varying the proportion of URS that get stents.

Results

Overall for all scenarios, there was a significant cost difference between the two strategies. In scenarios 1 and 2 there was a similar magnitude of cost difference of around £2,300. This was mainly being driven by the difference in primary intervention costs because URS is a much more expensive procedure. The cost of stents was also making URS a more expensive strategy because stents were much more likely following a URS. Although there were additional downstream resources from the initially less effective intervention of SWL, this did not offset the large difference in primary intervention costs. This was because although there are more retreatments and ancillary procedures in the SWL arm, these procedures are cheaper than URS retreatments or ancillaries, even though they apply to more people, which led to balancing out of downstream costs in the base case. Adverse events had little impact on the overall results. The incremental cost of scenario 3 was smaller than in the other scenarios (£1,212). This is being driven by a big difference in the ancillary procedure probabilities: there are many more ancillary procedures for SWL, which reflects that the success probability of the initial procedures is further apart than in the other scenarios. This result is also being driven by the types of ancillary procedures (which were taken from the study) in each strategy, which for URS were mostly SWL which is the cheapest procedure, and for SWL some ancillaries were PCNL, which is the most expensive procedure, thereby closing the cost gap further between the two strategies. A summary of the results of each scenario can be seen in Table 28.

Table 28

Results – Scenarios 1, 2 and 3 - total costs per person.

Sensitivity analyses varying the effectiveness of SWL in all 3 scenarios showed that the magnitude of the incremental cost was reduced as the effectiveness of SWL decreased. This can be explained because effectiveness has a negative relationship with the consequent retreatment and ancillary procedure probabilities, therefore more downstream resource use leads to higher SWL cost and lower incremental cost (see blue section of Table 29 for an example of this from scenario 2). A threshold analysis on the cost per session of SWL also showed this would have to be very high to make the comparisons cost neutral (ranging from £1,609 to £2,708 across the scenarios).

In scenarios 1 and 2, the retreatment and ancillary probabilities were pooled because of heterogeneity in these outcomes and differences between studies in criteria for deciding what procedures would be used if primary treatment failed. Assumptions were made varying what the procedures would be for the pooled probability of downstream resource use. This showed that the magnitude of the incremental costs were sensitive to the types of procedures because their costs can vary (in scenario 1 this was as low as £1,879). Varying the proportion of those having a URS that would have stents, and also assuming 2 primary sessions for SWL also had an impact on the incremental cost (the lowest incremental cost being in scenario 3 where 0% stent use led to an incremental cost of £760). However no sensitivity analyses varied the costs enough to make the strategies cost neutral.

The exploratory QALY work (scenario 2 and 3) was informative in exploring whether URS would be a cost effective alternative. In scenario 2, the QALY work showed that the quality of life difference between a stone free and non-stone free individual would need to be 27.8 for URS to be cost effective. This is not a physically possible value even taking the difference between the best and worst possible health states on the EQ-5D. This was explored further when the effectiveness of SWL was varied. This showed that as the effectiveness of SWL decreased, this drove down the QALY gain needed for URS to be cost effective. However, using the same method of applying that gain only to those people who would be initially stone free with URS over SWL, showed that the quality of life difference needed between a stone free and non-stone free health state was still outside the possible range on the EQ-5D (1.594) (see yellow section of Table 29). One problem with this is the short timeframe of the studies that was used to derive the quality of life gain. This was an average of 2 weeks for the studies in scenario 2 which means that the QoL part of the QALY has to be very large to compensate for the small timeframe this has to come from. A 2-way sensitivity analysis varying both the effectiveness and the time to further treatments (as it was assumed the quality of life gain following initial effectiveness remained for the whole time period of the trials), showed that for longer durations between treatments, and lower effectiveness levels of SWL, there were some quality of life differences between the health states that would be possible. Whether these would be feasible gains however is another matter (see Table 30).

Table 29

Scenario 2: SA8 results – varying initial effectiveness of SWL.

Table 30

Scenario 2: 2-way sensitivity analysis varying time to further treatment and initial SWL effectiveness.

In scenario 3, the exploratory cost utility analysis (based on assumptions about timing of further treatments during the 3 month trial, and quality of life of someone with and without a stone taken from the literature) showed that the ICER would be over £150,000. Varying the effectiveness of SWL showed that at an effectiveness as low as 40%, the ICER was still above £60,000. A threshold analysis on what the utility of someone without a stone would need to be to make URS cost effective at the £20,000 threshold identified that this would need to be −0.596, which is just outside worst possible state on the EQ-5D.

There are a number of limitations to the analyses: some assumptions may be underestimating the total resource use involved in clearing a stone; a single or very few studies are informing some scenarios. Additionally, a cost utility analysis was not felt possible because: of many unknowns about the health outcomes side of living with a renal stone; and because of the lack of clarity about what is happening at different points in the pathway regarding primary procedures and retreatments in order to apply utilities, as a result many assumptions would have to be made.

The exploratory QALY work also has many caveats. It is uncertain what the quality of life differences actually are, how long they apply for and the frequency of peoples pain episodes, and when further treatments are happening. So we can only estimate whether URS is likely to be cost effective. It is also important to remember that we are referring to the general ureteric <10mm stone population here, which will be a mix of people with different levels and frequency of symptoms. This is why even if QoL differences between a stone free and non-stone free person are physically possible, this does not mean these are feasible values, when considering the average population in question.

The time frame that has been used in the exploratory QALY work for scenarios 2 and 3 is the time between having failed a retreatment and having further treatment, and this is the same regardless of strategy. Note that this is not the time to the primary treatment (which would also be a factor in practice that would be considered when a clinician is considering treatment options). Waiting times are variable within the NHS for both SWL and URS. This is dependent on many local factors such as availability of equipment and staff. For SWL specifically, whether a fixed site lithotripter or mobile one is available can lead to differences in waiting times. URS waiting times are also variable because of staffing and theatre list arrangements. Anecdotally, having a fixed site lithotripter means SWL could be undertaken in a shorter space of time than waiting for a mobile machine which tends to come to each hospital on a sessional basis. If SWL has a shorter waiting time than URS for example, then multiple retreatments might be undertaken within the same timeframe of waiting for surgery, which would close the gap in effectiveness between the two interventions. Additionally, further treatment after a failed treatment would be seen as less of a priority in the NHS than primary treatment, in which case waiting time could be many weeks. The longer the waiting time, the more time that people are living with a stone having failed the less effective treatment, and the more QALYs the initially effective treatment would accrue.

There may also be differences in QoL between the two interventions that haven’t been considered. For example, because of the nature of the interventions themselves: Perhaps URS has a higher initial decrement in QoL because it is invasive and involves general anaesthetic, but outweighing this might be the fact that there could be a shorter recovery time as it gets rid of the stone in one go. Alternatively, SWL may have a higher decrement in QoL because people remember the SWL treatment, it not being performed under anaesthesia, and therefore remember the uncomfortable nature of the shockwave treatment. However it is also more convenient for patients as they can arrange a time around their daily routine for the sessions. Another issue is that people are more likely to have stents inserted after a URS, and stents are uncomfortable and therefore have a quality of life impact (with side effects like pain and frequent need to urinate). This means that to have an achievable QALY gain for URS, the effectiveness difference between SWL and URS needs to be larger, in order for the QoL gain from the additional stone free individuals to counteract the QoL loss from stents. A recommendation has been made in the guideline as part of the stents after surgery review to discourage the use of stents after surgery as there was no evidence of benefit, therefore as the recommendation is implemented then there would be fewer people experiencing the QoL impact of stents.

Other factors influencing quality of life that haven’t been considered include the impact of an untreated ureteric stone. The risk of obstruction/infection is difficult to quantify as generally these are people that are excluded from trials. The population in question however is likely to be people who are having planned treatment, and therefore those that are considered emergency cases would be outside the population being discussed here. The goal from a clinical perspective is to treat a ureteric stone a soon as possible because obstruction can result in loss of renal function within 6 weeks. The risk of obstruction is not something that could be included in the analysis as it couldn’t be quantified, but this was a concern the committee raised with regards to the less effective intervention of SWL which would take longer to clear a stone because of multiple treatments needed.

In essence, the above are just examples, but there may be factors on the health outcomes side that have not been captured, and therefore the exploratory QALY work needs to be interpreted with caution. The results however show that the gains being calculated as needed are beyond feasible levels which provide some reassurance that URS is unlikely to be cost effective.

1.5.5. Unit costs

Table 31

Intervention costs.

1.5.6. Economic considerations: trade-off between net clinical effects and costs

Renal stones <10mm: URS vs SWL

Methods

Given that

• the ureteric <10mm analysis showed that URS is unlikely to be cost effective, even when larger effectiveness differences were assumed between the strategies,
• and also comparing across the clinical review data for the three groups, which showed the effectiveness not to be too dissimilar

It was inferred that simpler cost offset calculations would be adequate in helping to infer the likelihood of the cost effectiveness of the more expensive treatments. The cost offset calculations only incorporate the cost of the initial interventions, and retreatment and ancillary procedures. What is being tested as to whether costs offset each other is the difference in initial intervention costs traded off against the difference in downstream resource use of retreatments and ancillary procedures. As the more expensive intervention is also more effective, which in turn leads to lower downstream resource use. Therefore the purpose is to see whether the downstream resource use will offset the difference in upfront intervention costs. Note that it is not clear if this is the cost that would make everyone stone free, as this depends on the endpoint of the studies that the clinical data is a summary of. So there are limitations to the approach in terms of potential underestimation of cost, however these calculations are meant to be interpreted as informal cost calculations using the available clinical data. Also, it may not be the case that the aim is to get someone stone free, as this depends on their symptoms and size of stone for example.

Assumptions were made about the number of sessions that constitute a primary treatment and how many constitute a retreatment (together making a course of treatment - note that clinically a course of treatment is offered as the ‘primary treatment’ which is usually up to 3 sessions for a stone in the kidney. So the clinical terminology may not be the same as the terminology used for the purposes of the costings – see full analysis write-up in Appendix 1 for more detailed descriptions).

Additionally, various scenarios have been assumed where the type of ancillary procedure is varied to see the iimpact on costs.

The summary of the clinical review data for this group showed that the effectiveness of URS is lower for small renal stones than it was for small ureteric stones, with SWL effectiveness remaining similar. Meaning the incremental effectiveness between the two interventions is smaller for small renal stones than for small ureteric stones. This implies that there will be less benefit of URS above that of SWL compared to the ureteric group, as fewer people will be initially stone free with URS, and so there will be less people achieving an increase in QoL early on in the pathway. Also as more resource use would be required downstream in the URS arm to get everyone stone free, then this would lead to higher costs also. The result of this is likely to be an even bigger cost divide between the interventions and a smaller difference in QALYs, compared to the ureteric group.

Additionally, as the ureteric analysis was a costing analysis primarily, with the QALY work being exploratory, then the conclusion can only be an estimate of whether the intervention is feasibly cost effective, and therefore simpler costing calculations would still allow exploratory work around the feasibility of cost effectiveness. This was done using four different timeframes that the initial effectiveness difference between the interventions would apply for 1,2,3 and 4 months for illustration.

Furthermore, as another potential source of data to assist in illustrating the costs of an SWL strategy, UK audit data from the BAUS (British association of Urological Surgeons) Endourology national SWL practice and outcomes audit³¹ was analysed and costs applied to identify the cost of treating people with SWL using real data.

The audit is a snapshot of current SWL practice across the UK in 2017. This involved all units undertaking SWL across the country being asked to recruit 10 consecutive new patients with renal stones attending for SWL and submit data over a 6 month period. The raw data was obtained through the committee, and analysed to crudely obtain the cost of SWL treatment by costing up the resource use involved in providing SWL including the primary treatments and downstream resource use. Note that as this audit only includes renal stones, a similar analysis could not be undertaken for the ureteric analysis. In total there were 141 patients suitable for evaluation in the dataset, with 101 patients having renal stones <=10mm, and 40 having renal stones 10-20mm.

The dataset reports information such as the status at review 3 months and 6 months following the first SWL treatment, and the subsequent management decision following the 3 and 6 month reviews. The status of the patient at review is broken down into 4 categories: ‘stone free’, ‘stone fragments <2mm in maximal diameter’, ‘stone fragments 2-4mm in maximal diameter’, and ‘stone fragments >4mm in maximal diameter’. Stone free using this dataset has been defined as patients in the ‘stone free’ and ‘stone fragments <2mm in maximal diameter’ category. The 3 month status of the patient and subsequent management decided at 3 months are the source of information on resource use, which costs were attached to. It is acknowledged that omitting the 6 month data may lead to an underestimate of the resource use of an SWL strategy if further resource use is consumed after 3 months. However, at 6 months more people were lost to follow up or the status was blank which would have led to fewer patients having outcomes that could be costed. Additionally, as the subsequent management at 3 months was included in the costings, which included those who had interventions planned, then if the 6 month outcome was that the intervention had been undertaken, then this would have already been accounted for. Therefore this was unlikely to make a large difference.

Results

With one session assumed for primary treatment and 2 for retreatment (making a total course of 3 treatments for those that have retreatments), and costing up the retreatment and ancillary procedures showed a range of cost offsets from £988 (assuming retreatment and ancillary probabilities are pooled and URS is the secondary procedure) to £1,537 (assuming the ancillary is URS for SWL group, and PCNL for URS group). This means that URS is still the more expensive strategy overall, as the difference in initial costs of performing the procedures are not being offset by the higher downstream resource use of SWL (i.e. taking into account downstream resource use still leads to a positive value, meaning the URS cost is still higher than the SWL cost). The main difference in cost is again from the difference in primary procedure costs.

Using the same back-calculations for the exploratory QALY approach to find the quality of life difference needed between a stone free and non-stone free health state, assuming an effectiveness difference of 20%, showed that this QoL difference needed to make URS cost effective was within the possible EQ-5D range (i.e. below 1.594) when the time between treatments was over 3 months. In other words time is important because if people who failed SWL have to wait longer for further treatments, then URS needs a smaller quality of life gain to make it cost effective, because the immediate benefit of URS (as gets more people stone free) avoids a longer period of lower quality of life in the alternative strategy (SWL).

There are many limitations to these cost calculations: they omit parameters such as the use of stents, follow up, adverse events, and therefore are not a full analysis like the ureteric analysis. The exploratory QALY calculations can only demonstrate what QoL gains would be needed and are a crude way of inferring cost effectiveness. However we have the ureteric analysis as a reference point that can help with this, for example a renal stone is not likely to have as much of a quality of life impact as the stone has more room to move in the kidney, therefore there is less benefit to clearing the stone early. Therefore although there are many unknowns around the actual health outcomes, as in the ureteric analysis, there are also less risks to leaving the renal stone, and so we can infer that URS would not be cost effective for renal stones <10mm given there is still likely to be a substantial difference in costs, and also smaller benefit to be gained from clearing the stone in one go.

Renal stones tend to be offered a course of treatment of up to 4 sessions of SWL, whereas a ureteric stone would be offered up to 2. In which case more SWL sessions would close the incremental cost gap further between the two strategies, however this depends on many factors such as how successful each number of sessions is as not everyone would need 4.

This is where costing up resource use from the BAUS audit data could be helpful because analysis of this dataset showed that people had on average 1.87 sessions, and this led to a 48% effectiveness (stone free) at 3 months. Costing up the average number of sessions as well as the resource use from the subsequent management decided at 3 months led to an overall cost of around £1,300 per person. This is similar to that found from the total costs of the SWL strategy in the cost offset calculations. Although we have not analysed similar audit data for people undertaking URS, we know the cost of the strategy will be at minimum the cost of the surgery which is over £2,200, which is still higher than the £1,300 found from the analysis of SWL audit data. Therefore, with the use of real life audit data we can be more confident that the cost of an SWL strategy is still likely to be lower than that of a URS strategy.

Renal stones 10-20 mm: PCNL vs URS vs SWL

Methods

For the larger renal stones subgroup, there was data in the clinical review for all three types of surgery because there were three pairwise comparisons;:SWL vs URS, URS vs PCNL, and SWL vs PCNL. The clinical data for each intervention was based on taking the average probability as each intervention could have two sources of data from the three pairwise comparisons.

Two pairwise comparisons are made, the most expensive (PCNL) compared to the next most expensive (URS): the clinical review showed that the difference in effectiveness in terms of stone free rate is not too dissimilar between PCNL and URS. The retreatment and ancillary procedure probabilities show that URS has slightly higher probabilities but this can vary depending on the pairwise comparison that the data was taken from. PCNL is also more than twice as expensive as a URS. The other pairwise comparison was URS versus SWL for this subgroup, the summary clinical review data showed that the effectiveness difference is larger than that of the other subgroups. This may be because the effectiveness of SWL reduces as the stone size increases. There is also a large variation in SWL retreatment and ancillary rates, depending on which pairwise comparison these are from, but as expected, SWL leads to more downstream resource use which we assume is a consequence of lower effectiveness.

Cost offset calculations are undertaken for these two pairwise comparisons, using the same methods as the small renal stones group. Primary SWL is assumed to be a single session, and retreatment is assumed to be 3 sessions (because of the larger size of the renal stone). Given the retreatment probability for SWL this gives an average of 2.2 sessions.

Comparing PCNL to SWL was not deemed necessary because there is such a large difference in the primary costs of treatments alone that it can be inferred PCNL is highly unlikely to be cost effective against SWL, even though it is considered more effective.

The BAUS snapshot data was also analysed for this group (of which there were 40 patients), using the same methods as described for the small renal stone group.

Results

When comparing PCNL versus URS, the large primary cost differences were offset very little by downstream resource use, regardless of what procedure might be assumed as an ancillary (ranging from £2,782 to £2,986). This is because both procedures are highly effective, and the resulting small downstream costs are having a negligible impact on the initial intervention cost differences. The small effectiveness difference between the interventions is unlikely to create a large enough QALY gain to justify the large additional cost of PCNL.

When comparing URS with SWL, cost offsets ranged from £836 (assuming retreatment and ancillary probabilities are pooled and URS is the secondary procedure) to £1,391 (assuming the ancillary is URS for SWL group, and PCNL for URS group). This means that the difference in primary procedure costs are not being offset by difference in downstream costs, as URS still remains a more expensive strategy. Using the same back-calculations for the exploratory QALY approach to find the quality of life difference needed between a stone free and non-stone free health state to make URS cost effective, assuming an effectiveness difference of 30%, showed that the QoL difference was within the possible EQ-5D range when the time between treatments was over 2 months (i.e. smaller than 1.594).

The limitations are the same as those for the small ureteric analysis: they omit parameters such as the use of stents, follow up, adverse events. The exploratory QALY calculations can only demonstrate what QoL gains would be needed. A large renal stone may have more of a quality of life detriment than a smaller renal stone, but perhaps not as much as a ureteric stone. There is little data to be able to quantify this theory but this was discussed with the committee. Therefore although there are many unknowns around the actual health outcomes, as in the ureteric analysis, there are also less risks to leaving the stone, and so we can infer that URS would also not be cost effective for this group given there is still likely to be a substantial difference in costs.

Costing up resource use from the BAUS audit data showed that people had on average 2.2 sessions, and this led to a 35% effectiveness (stone free) at 3 months. This is lower than the smaller renal stone group. Costing up the average number of sessions as well as the resource use from the subsequent management decided at 3 months led to an overall cost of around £1,600 per person. This is similar to that found from the total costs of the SWL strategy in the cost offset calculations. With the use of real time audit data we can be more confident that the cost of an SWL strategy as demonstrated above is still likely to be lower than that of a URS strategy (as we know the cost of the strategy will be at minimum the cost of the surgery which is over £2,200.

Summary

More informal costing calculations for the renal stone groups of <10mm and 10-20mm, using both the clinical review, and UK SWL audit data to illustrate further real SWL costs, showed that there are still likely to be large cost differences between URS and SWL strategies that would not be offset by downstream resource use. Quality of life impact of a ureteric stone and concerns around safety of not clearing a stone soon enough are more applicable to ureteric stones than to renal stones. In which case smaller quality of life gains are expected for a renal stone from the more effective intervention, which would make it more difficult for the benefit to justify the costs. PCNL is also much more expensive than URS and both are similarly effective, meaning it is unlikely PCNL is cost effective.

See appendix 1 for full details of the costing work.

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Appendices