Less than 1% of all breast cancers occur in men, making this a rare disease among that patient population, and most treatment guidelines are based on outcomes and survival rates seen in women with the disease.
A recent study published in Cancer investigated the effects of adjuvant chemotherapy for early-stage breast cancer solely among men, with the overall population-based observational results showing the treatment provides benefits in both all-cause and breast cancer—specific mortality for men with invasive stage I to III disease. Less than 1% of all breast cancers occur in men, making this a rare disease among that patient population, and most treatment guidelines are based on outcomes and survival rates seen in women with the disease, with most men undergoing modified radical mastectomy.
Data on the 2731 men enrolled in the current study were extracted from the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) cancer database for cancers diagnosed from 1990 to 2014. More than two-thirds (66.9%) did not receive chemotherapy, a status that was confirmed with SEER claims, but all had surgery (ie, lumpectomy or mastectomy). Their median age was 67 (range, 10-104) years, and most (55.4%) were 60 to 80 years.
Overall study results show there was a 26% decrease in all-cause mortality (P < .001), a finding the authors deemed significant, and a 21% drop in breast cancer—specific mortality (P = .085) for men who received chemotherapy, as well as that age, tumor size, lymph node involvement, tumor grade, and progesterone receptor (PR) status help to predict the likelihood of a male patient receiving the treatment for his breast cancer.
“Chemotherapy did not improve the breast cancer—specific survival for all men with PR-positive tumors (P = .959),” the authors indicated. “[And because] HER2 status was available only for patients diagnosed after 2010 in this database, HER2 status was not included for analysis in the current study.”
Median follow-up was 121 months, and median overall survival (OS) was 117 months. Five- and 10-year measures were also taken, and these came in at 91.3% and 81.3%, respectively, for breast cancer—specific survival and 73.0% and 48.7% for OS.
For PR status, having PR-negative disease in particular translated to a hazard ratio (HR) of 0.50 (95% CI, 0.28-0.91; P = .023) for breast cancer—specific survival and 0.54 (95% CI, 0.37-0.77; P = .001) for OS among the men who received chemotherapy, indicating their better chances of benefiting from the treatment compared with the men who had PR-positive disease. Only among men with PR-positive stage II and III breast cancer did chemotherapy improve OS rates (HR, 0.78; 95% CI, 0.66-0.92; P = .004). More than 80% of breast cancers in men are the PR-positive subtype.
For this study, breast cancer—specific survival was the time from diagnosis to breast cancer–related death or last follow-up, whereas OS was the time from diagnosis to any-cause death or last follow-up. Logistic regression identified predictors of chemotherapy, and a Cox proportional hazards model identified factors associated with breast cancer–specific survival and OS.
“Due to a lack of recruitment, many clinical trials of male breast cancer have been terminated. Therefore, to our knowledge, there are few data regarding the administration of chemotherapy in men with breast cancer,” the authors concluded. “The results of the current study provided potential indications for adjuvant chemotherapy in the treatment of patients with early-stage male breast cancer based on the results from a large cohort.”
Because their results may have known and unknown biases, the authors recommend future prospective studies to confirm their results.
Pan H, Zhang K, Wang M, Ling L, Wang S, Zhou W. The effect of chemotherapy on survival in patients with nonmetastatic male breast cancer: a population-based observational study. Cancer. Published online July 24, 2020. doi:10.1002/cncr.32829