A new study has reported that the risk of a second estrogen receptor negative (ER-) breast tumor is very high after a first ER- breast cancer diagnosis, particularly among women with a strong family history of breast cancer. A recent study found an increased risk of contralateral ER- cancer after a first primary ER- breast cancer. Contralateral breast cancer refers to a tumor in the other, originally non-cancerous breast. The present study was intended to confirm this result, if possible, and to evaluate how the risk of a second in-breast cancer occurrence is affected by family history and hormonal treatment. The study included 4,152 women in a Swiss cancer registry who were diagnosed with breast cancer between 1995 and 2007. The number of second breast cancers by estrogen receptor status was compared with rates of breast cancer expected in the general population. A total of 63 of the women were diagnosed with a second breast cancer during the study period.

Women with estrogen receptor positive (ER+) first tumors were found to have a relatively low risk of a second breast tumor, presumably in part because treatment is effective in preventing in-breast recurrence. On the other hand, breast cancer survivors with ER- primary tumors had eight times the risk of an ER- second tumor. Women with a family history of breast cancer were found to have a tenfold higher risk of an ER- second tumor (whether the first tumor was ER+ or ER-), which increased to nearly 50-fold when the first tumor was ER-. Not surprisingly, treatment with anti-estrogen therapy (aromatase inhibitors, tamoxifen or both) decreased the risk of second ER+ tumors but not ER- tumors. The authors conclude that risk of a second ER- breast tumor is very high after a first ER- breast cancer diagnosis, particularly among women with a strong family history of breast cancer. Both the ER status of the first tumor and family history should be taken into account when deciding on frequency and type of follow-up after treatment ends and possible steps to prevent a second breast cancer occurrence.

Please see our articles on triple negative and hormone receptor positive breast cancer prognosis.