Tamoxifen boosts survival in male breast cancer

In men with breast cancer, treatment with tamoxifen prolongs disease-free survival (DFS), cutting the risk of recurrence or death by more than 60 percent, as shown in a study.

“Hormone receptor (HR) positivity is the basis for successful tamoxifen therapy in male breast cancer (MBC),” according to the authors. “In this study, 98.4 percent of the tumours were HR-positive. Oestrogen receptor (ER) and progesterone receptor (PR) positivity were observed in 97.4 percent and 91.9 percent of the patients, respectively.”

The finding that HR positivity is prevalent in the study population is in line with other reports showing an HR expression of >90 percent in MBC, they added. [Crit Rev Oncol Hematol 2017;113:283-291; Cancer Metastasis 2018;37:599-614; Breast Cancer Res Treat 2013;137:465-470; J Cancer Res Clin Oncol 2017;144:337-341; J Cancer Res Clin Oncol 2018;144:1347-1355]

In their study, the authors looked at 448 MBC patients (median age at diagnosis, 69 years; body mass index, 27.4 kg/m²). Most tumours were >20 mm (53.9 percent), were invasive ductal carcinoma of no special histological type (NST; 94.1 percent), and had an intermediate histological grade (65.3 percent). About 44 percent of the men were diagnosed with positive axillary lymph nodes. [Br J Cancer 2020;123:33-37]

The survival analysis included 316 men with HR-positive breast cancer, among whom 269 (85.1 percent) underwent treatment with tamoxifen. Notably, patients who did not receive the treatment showed significantly inferior DFS (p=0.002). The rate of recurrence or death was 22.6 percent with tamoxifen vs 13.9 percent with non-treatment. Bone was the most common site of recurrence, followed by locoregional sites, liver, lungs and/or pleura, distant lymph nodes, brain, and rectum.

In multivariable Cox proportional hazard models, tamoxifen reduced the risk of recurrence or death by 62 percent (hazard ratio [HR] for DFS, 0.38, 95 percent confidence interval [CI], 0.19–0.78; p=0.008). Factors related to a shorter DFS included undifferentiated grading (HR, 2.61, 95 percent CI, 1.34–5.05; p=0.005) and positive lymph nodes (HR, 2.87, 95 percent CI, 1.42–5.76; p=0.003).

“Importantly, we recently found out that the survival effect of tamoxifen treatment was comparable in both MBC and female breast cancer (FBC),” the authors said.

However, they acknowledged that tamoxifen was associated with various adverse effects, including gastrointestinal and cardiovascular problems, psychiatric disorders, erectile dysfunction, gynaecomastia, fatigue, musculoskeletal and connective tissue disorders, and thromboembolic events.

“Specific disorders, such as gynaecomastia and erectile dysfunction, have been described in men, whereas endometrial cancer and increased rate of fractures have been observed in women,” according to the authors. They noted that tamoxifen treatment in men has been recently associated with significantly increased risk of thrombotic events in comparison with the use of the drug for FBC. [Breast Cancer Res Treat 2004;83:77-86; Int J Cancer 2016;139:1715-1720]

The authors emphasized that tamoxifen’s safety should factor in during treatment decision.

“Whether prolonged tamoxifen treatment would be beneficial for a group of patients at high risk of recurrence should be investigated in future studies, which preferably cover extended periods, eg, 10 years. We will also use the present prospective cohort study to investigate whether prolonged tamoxifen treatment is indicated for MBC patients at high risk,” they added.