Male breast cancer patients have a later onset of disease and worse overall survival rates compared with female patients, according to a large international population-based study reported at the CTRC-AACR San Antonio Breast Cancer Symposium.
Breast cancer in men is rare, with an incidence rate of only 0.5% sto 1.0%, noted lead investigator Hui Miao, a PhD candidate in the Department of Epidemiology and Public Health at the National University of Singapore.
“Given the scarcity of breast cancer in men, few studies have assessed its prognosis, and no recent studies have evaluated trends in survival,” she said at her poster study.
Men Diagnosed Later
The new study involved 459,846 women and 2,664 men diagnosed with breast cancer in Denmark, Finland, Switzerland, Norway, Singapore, and Sweden between 1970 and 2007.
The overall incidence rates, adjusted to the World Standard Population, of breast cancer were 60.2 per 100,000 persons in women and 0.4 per 100,000 persons in men. Women were diagnosed with breast cancer at a median age of 61.4 years vs 68.9 years for men.
Among the 198,020 patients for whom information was available on stage, 75% of the women and 68% of men were classified as having Stage I or II.
A total of 91% of women and 86% of men underwent surgery, a difference that was highly significant, with a p value of less than 0.0001, Ms. Miao reported.
Also, 38% of women and 31% of men had radiotherapy, again a significant difference, she said.
The five-year cumulative survival rate was 66.2% for women and 53.0% for men.
Although the unadjusted relative risk of death over 15 years was 24% higher in men than women, after adjustment for such factors as country of diagnosis, age and year of diagnosis, stage, and treatment, men were found to be actually 26% less likely to die than women, Ms. Miao said.
“Differences in tumor characteristics and treatment appear to account for men's higher unadjusted higher risk of death. Females appear to be getting better treatment.”
Hormone Therapy One Explanation
Steven J. Isakoff, MD, PhD, of Massachusetts General Hospital Cancer Center said the fact that more men are eligible for hormone therapy with tamoxifen and/or aromatase inhibitors may be one reason they appear to do better once treatment is taken into account.
About 90% of men have tumors that are estrogen-receptor positive, he said. In contrast, only about 60% to 70% of women have hormone-driven breast cancers.
“In general, hormone-receptor-positive breast cancers are associated with longer survival,” he said.
Ms. Miao agreed. Still, in the study, 21% of women and 23% of men received hormonal therapy, a difference that was no significant.
The fact that men don't think they're susceptible to breast cancer and therefore don't perform breast self-examinations or get regular mammograms may account for their later stage at diagnosis, Dr. Isakoff hypothesized, adding that the older age of men at diagnosis “probably has to do with fact that many men develop obesity as they get older, which can contribute to increased estrogen levels.”