Adjuvant Hormonal Therapy for Breast Cancer and Risk of Hormone Receptor–Specific Subtypes of Contralateral Breast Cancer

¹Division of Public Health Sciences and ²Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, WA

^* To whom correspondence should be addressed. E-mail: cili{at}fhcrc.org.

	Abstract

Compared with the breast cancer risk women in the general population have, breast cancer survivors have a substantially higher risk of developing a second primary contralateral breast cancer. Adjuvant hormonal therapy reduces this risk, but preliminary data indicate that it may also increase risk of hormone receptor–negative contralateral tumors. We conducted a population-based nested case-control study including 367 women diagnosed with both first primary estrogen receptor (ER)–positive invasive breast cancer and second primary contralateral breast cancer and 728 matched control women diagnosed only with a first breast cancer. Data on adjuvant hormonal therapy, other treatments, and breast cancer risk factors were ascertained through telephone interviews and medical record abstractions. Two-sided statistical tests using conditional logistic regression were conducted to quantify associations between adjuvant hormonal therapy and risk of hormone receptor–specific subtypes of contralateral breast cancer (n = 303 ER+ and n = 52 ER- cases). Compared with women not treated with hormonal therapy, users of adjuvant tamoxifen for 5 years had a reduced risk of ER+ contralateral breast cancer [odds ratio, 0.4; 95% confidence interval (CI), 0.3–0.7], but a 4.4-fold (95% CI, 1.03–19.0) increased risk of ER- contralateral breast cancer. Tamoxifen use for <5 years was not associated with ER- contralateral breast cancer risk. Although adjuvant hormonal therapy has clear benefits, risk of the relatively uncommon outcome of ER- contralateral breast cancer may now need to be tallied among its risks. This is of clinical concern given the poorer prognosis of ER- compared with ER+ tumors. [Cancer Res 2009;69(17):6865–70]

Key Words: breast cancer, tamoxifen, estrogen receptor, progesterone receptor, contralateral breast cancer

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				Correction: Adjuvant Hormonal Therapy for Breast Cancer and Risk of Hormone Receptor-Specific Subtypes of Contralateral Breast Cancer Cancer Res., January 15, 2010; 70(2): 853 - 853. [Full Text] [PDF]