Comparative Net Survival Analysis of Men and Women With Breast Cancer in Japan: A Population‐Based Study

• DOI: 10.1111/cas.70068
• Publication Date: 2025-04-01T22:16:07Z
• Authors: Daisy Sibale Mojoo; Isao Oze; Hiroshi Tsuge; Yukari Taniyama; Yuriko N. Koyanagi; Sayaka Yamamoto; Megumi Hori; Kayo Nakata; Hiromi Sugiyama; Isao Miyashiro; Izumi Oki; Yoshikazu Nishino; Yuri Ito; Kota Katanoda; Akiko Shibata; Tomohiro Matsuda; Keitaro Matsuo; Hidemi Ito

ABSTRACTWhile male breast cancer (MBC) remains a rare and understudied disease, comparatively little is known about its prognosis in contrast to female breast cancer (FBC). There is a paucity of large population‐based studies comparing the prognosis of MBC patients to FBC patients in Japan. This study analyzed 181,540 breast cancer cases, 1058 (0.6%) males and 180,482 (99.4%) females, from 12 prefectures in Japan diagnosed between 1993 and 2011. Five‐ and ten‐year net survival (NS) were estimated and stratified by sex, period, age, stage, and histological groups. Excess hazard ratios (EHR) were adjusted for period, age, stage, and histological group. Cochran's Q test was utilized to assess heterogeneity across these factors. The overall 5‐ and 10‐year NS estimates for MBC patients were 90.7% (95% CI: 86.3%–93.7%) and 83.7% (95% CI: 72.2%–90.8%), respectively, while those for FBC patients were 88.3% (95% CI: 88.1%–88.5%) and 79.1% (95% CI: 78.7%–79.4%), respectively. The survival of MBC patients was comparable to that of FBC patients, with EHR of 0.88 [95% CI: 0.70–1.09] and 0.86 [95% CI: 0.69–1.07] for 5‐ and 10‐year survival, respectively. Heterogeneity analysis revealed no significant sex‐based differences in survival across these strata. This study offers a comprehensive analysis of breast cancer survival in Japanese men and women and enhances understanding of MBC prognosis relative to FBC.