Background: Industry funders can simply provide money or collaborate in trial design, analysis or reporting of clinical trials. Our aim was to assess the impact of industry collaboration on trial methodology and results of randomised controlled trials (RCT).

Methods: We searched PubMed for oncology RCTs published May 2013 to December 2015 in peer-reviewed journals with impact factor > 5 requiring reporting of funder role. Two authors extracted methodologic (primary end-point; blinding of the patient, clinician and outcomes assessor; and analysis) and outcome data. We used descriptive statistics and two-sided Fisher exact tests to compare characteristics of trials with collaboration, with industry funding only, and without industry funding.

Results: We included 224 trials. Compared to those without industry funding, trials with collaboration used more placebo control (RR 3·59, 95% CI [1·88-6·83], p < 0001), intention-to-treat analysis (RR 1·32, 95% CI [1·04-1·67], p = 02), and blinding of patients (RR 3·05, 95% CI [1·71-5·44], p < 0001), clinicians (RR 3·36, 95% CI [1·83-6·16], p≤·001) and outcomes assessors (RR 3·03, 95% CI [1·57-5·83], p = 0002). They did not differ in use of overall survival as a primary end-point (RR 1·27 95% CI [0·72-2·24]) and were similarly likely to report positive results (RR 1·11 95% CI [0·85-1·46], p = 0.45). Studies with funding only did not differ from those without funding.

Conclusions: Oncology RCTs with industry collaboration were more likely to use some high-quality methods than those without industry funding, with similar rates of positive results. Our findings suggest that collaboration is not associated with trial outcomes and that mandatory disclosure of funder roles may mitigate bias.