Adherence to and tolerance of low-dose tamoxifen versus standard-dose tamoxifen in women at increased risk of breast cancer.

[OBJECTIVE] Tamoxifen 20 mg daily for 5 years decreases breast cancer (BC) risk by 49% in women with a family history of the disease and by up to 85% in women with a personal history of high-risk lesions. The TAM-01 study demonstrated that patients with ductal carcinoma in situ (DCIS), lobular carcinoma in situ (LCIS), atypical ductal hyperplasia (ADH) or atypical lobular hyperplasia (ALH) had a 50% reduction in cancer events with 5 mg daily for 3 years. We aimed to determine whether the use of low-dose tamoxifen (LDT) leads to better adherence and tolerance than standard-dose tamoxifen (SDT).

[STUDY DESIGN] A retrospective chart review of women with DCIS, LCIS, ADH/ALH, increased risk due to family history of breast cancer, or high-risk gene mutation was performed. Patients were grouped as SDT or LDT. Patients who declined medications were the control.

[RESULTS] Among 256 patients, 46% (N = 117) initiated LDT, 21% (N = 55) SDT and 33% (N = 84) declined tamoxifen. 59% of patients on LDT completed 3 years of therapy compared with 47.3% of SDT patients. Five women (2.0%) developed recurrent cancer, and 4 women (1.6%) developed a new malignancy. Vasomotor symptoms were the most commonly reported adverse events, affecting over 40% of patients in both tamoxifen groups.

[CONCLUSION] LDT was well tolerated, with a trend toward increased likelihood of completion of therapy. Patients with more than one indication for tamoxifen were more likely to complete therapy. Side-effects were similar in the two treatment groups, although severity was not able to be assessed due to the retrospective study design.