Epidemiology of male breast cancer

Abstract

Background: Due to its rarity, few studies have characterized the epidemiology of male breast cancer. The purpose of this study was to determine survival and risk factors for male breast cancer in a large U.S.

Methods: In this study, 19,795 male patients with breast cancer were identified from the National Cancer Database (2004-2014). Patient demographics, tumor characteristics and treatments were analyzed by using descriptive statistics. We used multivariate Cox regression and Kaplan Meier analysis.

Results: Over 10 years, the incidence of male breast cancer increased from 7.2% to 10.3%, while mortality decreased from 11% to 3.8%. Socioeconomic factors predicting mortality included income medium, and high vs low (HR = 0.78; 0.68), private vs no insurance (HR = 0.73) and the academic research facility vs community cancer center (HR = 0.79). Significant predictors of all-cause mortality included age (HR = 1.04), tumor size (HR = 1.01), hormone receptor expression (HR = 0.8) and cancer stage I vs II, III, and IV at the time of diagnosis (HR = 1.5, 2.7, 4.4, 9.9 respectively). Other predictors of mortality include surgery (HR = 0.4), chemotherapy (HR = 0.8), radiation (HR = 0.8), and hormonal therapy (HR-0.8).

Conclusions: Socioeconomic factors, cancer stage, tumor characteristics (size and grade), and high Charlson-Dayo score contributed to higher mortality among male patients diagnosed with breast cancer. Surgery was most effective, followed by radiation, chemotherapy, and hormonal therapy. Patients with positive ER or PR expression demonstrated better survival. Adjusting for socioeconomic factors, biomarker identification and timely, appropriately chosen treatment are likely to reduce the risk for mortality.

Keywords: Epidemiology; Male breast; Mortality; NCBD database; Survival.

Fig. 1

Percentage of the cases for male breast cancer per year out of total patients diagnosed with breast cancer from 2004 through 2014 (N = 19,795). Rates of diagnosis and mortality in male breast cancer. Orange line: Total cases of male breast cancer were graphed from 2004 to 2014. Blue line: Mortality rates for male breast cancer was calculated for the same time frame.

Fig. 2

Kaplan Meier survival probability of male breast cancer patients who received either surgery, chemotherapy or radiation following initial diagnosis. The numbers of patients in each category are shown on the bottom of each graph. (a) Survival probabilities for patients who underwent surgery were calculated. The solid blue line is survival of patients who did not receive surgery and the red, dashed line is of the patients who underwent surgery. (b) Survival curves for patients who received chemotherapy treatment (red line) vs. those who did not receive chemotherapy (blue line). (c) Survival curves for patients who received radiation treatment (red line) comparing those who did not (blue line). Dx: diagnosis. p-values are shown in the upper, right-hand corner of each graph.

Fig. 3

Survival probabilities for male breast cancer patients whose tumors expressed ER or PR and for those who received hormonal therapy. (a) Patients whose tumors were ER positive (red line) compared with those who tumors were ER negative (blue line). (b) Patients whose tumors expressed PR (red line) compared with those whose tumors were PR negative (blue line). Dx, diagnosis. (c) Patients who received hormonal therapy were compared with those who did not receive hormonal therapy. Dx: diagnosis. p-values are shown in the upper, right-hand corner of each graph.