Men’s Health Week 2019: Male Breast Cancer Research Updates

Thanks to BCRF-supported research, we are learning more about this rare and understudied disease.

Breast cancer is the most commonly diagnosed cancer in women and the second most common cause of cancer death in women. However, each year, more than 2,500 new cases of breast cancer are diagnosed in men, with 500 men dying from their disease each year.

Because male breast cancer is so rare, most men and their physicians do not consider breast cancer when they see or feel something unusual in the chest. This can result in a later diagnosis and higher risk of death.

The rare occurrence of breast cancer in men also makes it difficult to study as few men are available or even recruited to participate in clinical trials. That is beginning to change, as more trials are including men and there is an increased effort to understand the molecular and genomic landscape of male breast cancer.

BCRF was at the vanguard of this trend with its support of the International Male Breast Cancer Program, the largest study in the world on male breast cancer that was launched in 2006 and led by BCRF researchers Drs. Fatima Cardoso and Sharon Giordano. Because of this support we are learning more about this rare and understudied disease.

What we’ve learned

Male breast cancer is different from female breast cancer. In a retrospective analysis of 1,822 men with breast cancer, Dr. Cardoso and her colleagues reported that male and female breast cancers are different in terms of histology and grading. The study also showed that while over 90 percent of male patients had estrogen receptor (ER)-positive breast cancer, only 77 percent of them received endocrine therapy after surgery, which is the standard of care of ER-positive breast cancer

Male breast cancers are molecularly different from female breast cancer.  Breast cancer is classified into different subtypes based on molecular profiles of the tumors. A molecular profile is a snapshot of the genes or molecular programs that are promoting the tumor growth and can help to guide the appropriate treatment for each patient.

A molecular profiling analysis of 152 breast tumor samples from men identified five intrinsic subtypes of male breast cancer with various gene expression profiles. One of these subtypes has not been seen in women. Other research by BCRF investigators has also shown male breast cancers harbor different gene mutations than those found in female breast cancer.

Treatment of breast cancer in men. Most breast cancers in men are driven by estrogen, as are breast cancers in women. Treatment for men typically includes the antiestrogen drug tamoxifen along with surgery and radiation therapy. The recent approval of the CDK 4/6 inhibitors drug, Ibrance® (palbociclib) for men with advanced or metastatic breast cancer provides a new option for men with late-stage disease. Ongoing studies are uncovering potentially new targets for breast cancers in men, including unique mutations in the estrogen receptor gene not seen in female breast cancer.

What’s next?

Since few men are enrolled in clinical trials, treatment recommendations are frequently based on the subtype of breast cancer alone. In the final phase of the International Breast Cancer Program, Dr. Cardoso’s team will initiate a clinical trial to test a combination hormone therapy in men with breast cancer. They will continue to conduct molecular profiling on the more than 500 tumor samples from the retrospective component of the study.

Because of increased awareness and the activity of male breast cancer advocates, the study of male breast cancer has increased, and research will continue to fuel discoveries that will lead to better outcomes in men with breast cancer.

Additional resources

American Cancer Society: Breast Cancer in Men

Male Breast Cancer Coalition: Patient support and resources

ASCO interview  with Dr. Giordano

BCRF Facebook Live interview with Dr. Cardoso