Men may be more likely than women to die after being diagnosed with breast cancer, particularly during the first 5 years after diagnosis, a new study suggests. In the study, the 5-year overall survival rate after a diagnosis of breast cancer was 77.6% for men, compared with 86.4% for women, researchers reported in JAMA Oncology on September 19. The findings add to previous research showing differences in death rates between men and women with breast cancer while also providing information about some of the factors that may contribute to the disparity between the sexes. One factor identified by the authors was the lack of adequate treatment for many men with breast cancer, a phenomenon known as undertreatment. Another was the later diagnosis of the disease in men than in women. Differences in clinical characteristics, such as the types and stage of breast tumors, age at diagnosis, and cancer treatment between men and women with breast cancer played a major role, accounting for 63% of mortality disparity, the researchers reported. However, after all those factors were accounted for, male patients still had 19% higher chance of dying than female patients within 5 years of diagnosis. “We were not able to investigate other known or suspected contributors for the disparity in death rates in this study, such as compliance to cancer treatment, tumor genetics, and lifestyle factors, such as obesity, smoking, and alcohol use,” said Xiao-Ou Shu, M.D., Ph.D., of Vanderbilt-Ingram Cancer Center, who led the research. “If we want to learn more about why outcomes of male breast cancer differ from those of female breast cancer, then we need more studies that focus on men with the disease,” Dr. Shu continued. These studies should include multiple outcomes, such as cancer remission, recurrence, and death rates from breast cancer and all causes, she added.