Need for high-quality studies in health technology assessments: the case of a systematic review of treatment for retinoblastoma.

OBJECTIVES: The aim of this study was to conduct a systematic review of the evidence for treatments for retinoblastoma in children.
METHODS: Seventeen electronic databases were searched. Two reviewers independently selected studies. Studies of participants diagnosed with childhood retinoblastoma, any interventions, and all clinical outcomes were eligible. Randomized and nonrandomized controlled trials and cohort studies with clear comparisons between treatment groups were included. Methodological quality was assessed.
RESULTS: Thirty-one observational comparative studies were included, of which twenty-seven were retrospective. The methodological quality was generally poor, with a high risk of selection bias in all studies. Although there were high levels of treatment success in many of the studies, due to the limitations of the evidence identified, it was not possible to make meaningful and robust conclusions about the relative effectiveness of different treatment approaches for retinoblastoma in children.
CONCLUSIONS: Good quality randomized controlled trials are required. Where controlled trials are not feasible, only high quality prospective, nonrandomized studies should be given consideration, due to the generally higher risk of bias in retrospective studies.