Purpose: The vast majority of epidemiological studies in cancer are observational. However, inadequate reporting of the published observational studies (OS) may restrict the generalizability and credibility of study results. The aim of this study was to evaluate the reporting quality of OS concerning cancer.
Methods: PubMed was searched for systematic reviews (SRs) of OS involving cancer published from January 2008 through February 2009. The citations provided in the SRs were evaluated for their reporting quality according to the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) statement, a checklist of items that are considered essential for good reporting of OS. The evaluation was focused on 25 methodological items/sub-items. The effect of journals' ranking in quality of reporting was also evaluated.
Results: The search identified 244 eligible OS included in seven SRs. Nine items/sub-items were reported by more than 90% of studies and 16 items/sub-items were reported by more than 70%. Some essential methodological aspects of OS (such as matching, absolute risks, missing data and flow diagram) were underreported. Significant differences were found among the seven SRs in the majority of the items. High and lower ranked journals were different only in reporting of results estimates and precision.
Conclusions: The quality of reporting in OS in cancer was considered satisfactory, although certain items were underreported. Further improvement of reporting may enhance the validity of observational research.