Failure to address potential bias in nonrandomised controlled clinical trials may cause lack of evidence on patientreported outcomes: a method study

Objectives: We conducted a workup of a previously published systematic review and aimed to analyse why most of the identified non-randomised controlled clinical trials with patient-reported outcomes did not match a set of basic quality criteria. Setting: There were no limits on the level of care and the geographical location. Participants: The review evaluated permanent interstitial low-dose rate brachytherapy in patients with localised prostate cancer and compared that intervention with alternative procedures such as external beam radiotherapy, radical prostatectomy and no primary therapy. Primary outcome measure: Fulfilment of basic inclusion criteria according to a Participants, Interventions, Comparisons, Outcomes (PICO) framework and accomplishment of requirements to contain superimposed risk of bias. Results: We found that 21 of 50 excluded non-randomised controlled trials did not meet the PICO inclusion criteria. The remaining 29 studies showed a lack in the quality of reporting. The resulting flaws included attrition bias due to loss of follow-up, lack of reporting baseline data, potential confounding due to unadjusted data and lack of statistical comparison between groups. Conclusions: With respect to the reporting of patient-reported outcomes, active efforts are required to improve the quality of reporting in non-randomised controlled trials concerning permanent interstitial low-dose rate brachytherapy in patients with localised prostate cancer.