Re: Estrogen Receptor Status of Primary Breast Cancer Is Predictive of Estrogen Receptor Status of Contralateral Breast Cancer

Extract

The recent paper by Swain et al. ( 1 ) showing a high degree of concordance between the estrogen receptor (ER) status of first primary and contralateral breast cancers is of considerable biological interest, particularly because gene expression studies have shown that a large number of genes distinguish ER-positive from ER-negative breast cancers ( 2 , 3 ). In the study by Swain et al., only women diagnosed before the age of 50 did not receive tamoxifen. Thus, only in that group of women can the biology of the two breast cancers be truly studied. Notably, concordance was seen in 50 of the 62 pairs of cancers in this group of women (in 19 women, both cancers were ER negative, and in 31 women, both cancers were ER positive), leaving only 12 women (eight women with an ER-negative first cancer and an ER-positive second cancer and four women with an ER-positive first cancer and an ER-negative second cancer) in which the first and second cancers were discordant for ER status. The median time from randomization to contralateral invasive breast cancer was 4.66 years (range = 0.26–10.3 years).