Results from the largest series of male breast cancer cases ever studied showed that overall survival for male patients with breast cancer was significantly improved over the duration of the study, but the improvement was not as good as that for female patients with breast cancer, according to research presented at the 2014 San Antonio Breast Cancer Symposium.

“Although we saw a significant improvement in overall survival for male breast cancer patients over time, the prognosis for men with breast cancer has not been improving as much as for women with the disease,” said Fatima Cardoso, MD, director of the breast unit at the Champalimaud Cancer Center in Lisbon, Portugal. “This is largely because male breast cancer is a rare disease—it accounts for just 1% of breast cancers—and we know very little about its biology and how best to treat patients.

“Our results provide new insight into the clinical and biological characteristics of breast cancer in men, and show that they are not the same as those previously reported for breast cancer in women,” continued Cardoso. These results tend to show that men with breast cancer are not well managed in the clinic. For example, even though most male breast cancers are ER-positive, only 77% of patients received endocrine therapy such as tamoxifen.

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“We also found that even though 56% of male breast cancers are diagnosed when the tumors are very small, only 4% of patients had breast-conserving surgery; most had a mastectomy, which significantly impacted their quality of life,” reported Cardoso.

Tumor analyses to determine the biological characteristics of male breast cancer showed that 92% were positive for the estrogen receptor (ER), 5% were positive for HER2, and 1% were triple-negative. In women, approximately 70% of breast cancers are ER-positive, 20% are HER2-positive, and 10% to 15% are triple-negative.

The first goal of the Male Breast Cancer International Program was to analyze the largest series of male breast cancer cases ever studied. Cardoso and her colleagues enrolled 1,822 men with breast cancer treated between 1990 and 2010 at 23 centers in nine countries. Clinical data for the patients were all analyzed at the European Organization for Research and Treatment of Cancer headquarters and tumor samples were analyzed at three locations—two in Europe and one in the United States. According to Cardoso, it was very important that the tumor samples be analyzed in central locations using the same protocols so that variation in analyses could be minimized.

“We are continuing to analyze the tumor samples that we collected during this first part of the project,” said Cardoso. “But we have also begun part two, which is the prospective register of all men diagnosed with breast cancer in many European, Latin American, and North American countries during a 2-year period. This will allow the collection of a current series of these patients and assert the ability of the network to run clinical trials in this rare disease. We also hope to soon begin part three of the project, which will be a clinical trial to test a potential new treatment option for men with breast cancer.”