We seek to investigate the presence and magnitude of potential bias in PRO outcomes when patients have knowledge of the treatment they are receiving. In oncology, there are many drugs that share the same mechanism of action, and which consequently get approved for the same indications. These approvals are often based on trials which were designed with similar populations and arms, making them excellent candidates for meta-analyses. Although these sets of trials share many features, occasionally some of the trials in the same indication will be double-blind while the others are open-label. We utilize these groups of studies to investigate whether there were any notable differences in patient-reported outcomes between the double-blind and open-label trials in the same indication. We anticipate that drop-out will be higher in the control arms when the trial is open-label, and that there may be a “placebo effect” when the patients have knowledge of the treatment they are receiving. If there is a strong bias owing to patients’ knowledge of treatment assignment, we anticipate that treatment effects will be consistently larger for open-label trials than double-blind trials.