Concerning the CYP17 MspA1 polymorphism and breast cancer risk: a meta-analysis

Abstract

Ye and Parry (2002) recently presented a meta-analysis of the CYP17 MspA1 polymorphism and breast cancer. While it is appealing to come up with a summary effect across studies, a meta-analysis is not the best approach to resolve the CYP17– breast cancer association. A meta-analysis for this set of data is of questionable validity, as the studies that have been done employ different designs and include a mixture of ages and ethnicities. Regarding the published meta-analysis, we noticed several errors in reporting the number of advanced cases and controls in Table II. In some instances, this led to an incorrect specification of control groups when estimating the effect of the CYP17 A2 allele for advanced breast cancer. For some of the studies, Ye and Parry used odd ratios (ORs) that were computed by comparing advanced to localized cases, rather than advanced cases to unaffected controls. The two methods address different questions regarding the role of CYP17 in the etiology of breast cancer. When summarizing data from previous articles, Ye and Parry did not include data from our recent study (Feigelson et al., 2001) in their calculation of a summary estimate for advanced breast cancer (Table II in Ye and Parry, 2002). Our nested case control study included 615 stage 1 cases, 235 cases of stage 2 or greater (‘advanced’) and 1508 controls (in situ cases and those of unknown stage were excluded). These 235 cases represent the largest number of advanced cases from a single study in the published literature to date. Among advanced cases we found that compared to A1/A1 women, those with the A1/A2 genotype had a RR 1.29 (95% CI