Compliance With Tamoxifen in Women With Breast Cancer and a BRCA1 or BRCA2 Mutation

Abstract

TO THE EDITOR: Tamoxifen, or another type of adjuvant hormonal therapy, is often prescribed to women who are diagnosed with estrogen receptor–positive breast cancer, with the goal of preventing local and distal recurrence. Women with a BRCA1 or BRCA2 mutation may also benefit in that tamoxifen use is associated with a reduction in second primary breast cancer, as well. Recently, Hershman et al showed that, of 8,769 patients with breast cancer who began a course of tamoxifen, only 68% completed 4.5 or more years of use. This report prompted us to ask whether the experience of women with a BRCA1 or BRCA2 mutation was similar. From a registry of BRCA1 and BRCA2 carriers, we identified 461 women who had been diagnosed with breast cancer at least 5 years prior (between 1970 and 2004) and who initiated a course of tamoxifen (n 301, BRCA1; n 160, BRCA2). Women who experienced a recurrence in the first 5 years after initial diagnosis were excluded. The duration of tamoxifen use was derived from a self-completed questionnaire. Two hundred ninety-two women (63%) received tamoxifen for 4.0 or more years, and 238 women (52%) received tamoxifen for 4.5 years or more. The mean duration of tamoxifen use (truncating the maximum use at 5.0 years) was 3.7 years. The proportions of women who received tamoxifen for 4.0 or more years are listed in Table 1. To establish which factors independently predicted the completion of tamoxifen use, we conducted an unconditional logistic regression by using the variables in Table 1. Including variables with a P value of .05 or less for significance, the predictive factors in the final model were postmenopausal at diagnosis (odds ratio [OR], 1.75; 95% CI, 1.14 to 2.66; P .01, v premenopausal); Jewish ethnicity (OR, 2.81; 95% CI, 1.59 to 4.96; P .001, v other white); French-Canadian ethnicity (OR, 2.99; 95% CI, 1.21 to 7.37; P .02, v other white); Polish ethnicity (OR, 3.07; 95% CI, 1.76 to 5.36; P .001, v other white); and a BRCA2 mutation (OR, 1.85; 95% CI, 1.16 to 2.94, v a BRCA1 mutation). On average, premenopausal women took tamoxifen for 3.5 years. In summary, tamoxifen use among women with breast cancer and a BRCA1 or BRCA2 mutation is suboptimal, and patterns of use are similar to those of noncarriers. The reasons for early termination of tamoxifen in premenopausal patients with hereditary breast cancer are unknown and should be explored further.