“…There is some overlap between a study of data from the San Francisco Bay region during 1973-1993 (Robbins, Whittemore, & Thom, 2000) and a study of four SEER centers including San Francisco during 1987-1991(OakleyGirvan et al, 2003, with both studies being based on all men with prostate cancer. But we do not see how such limited overlap in the data used by these four studies justifies the exclusion of Polednak (2003), Robbins et al (2000), and Oakley-Girvan et al (2003) and the consequent loss of unique information from the Sridhar et al (2010) analysis. Stepping back from the detail, we would hope that it is uncontroversial to say that the incorporation of overlapping cohort studies within a meta-analysis is not straightforward.…”