THE ANNUAL INCIDENCE of male breast cancer in the United States is dwarfed by the rate among women. Yet, for the estimated 2,670 men who will be diagnosed with breast cancer this year, life-extending and life-enhancing treatments are crucial.1 To help reduce knowledge gaps and improve mortality and morbidity outcomes, ASCO recently gathered a group of experts to develop its first consensus guideline on interventions for breast cancer in men.2
An Uphill Challenge
Michael J. Hassett, MD, MPH
FROM THE OUTSET, the expert panel faced a unique barrier, given the rarity of breast cancer in men. “Sometimes, when there’s lots of complicated information out there, we develop guidelines to make sense of the data and come up with the right path forward. This was not that case,” said Michael J. Hassett, MD, MPH, of Dana-Farber Cancer Institute, and Guideline Co-Chair. “We don’t have a lot of clinical data for male breast cancer—[less than] 1% of all breast cancer occurs in men—and we still need a way of treating them. The goal of this guideline was to combine the limited data we have for breast cancer in men with our best understanding of breast cancer in women to develop consensus recommendations that apply to all of the clinical scenarios experienced by men.”
Using a two-step approach, the panel first discussed recommendations that, based on available data and clinical experience, they believed should coincide with practices for women with breast cancer. When recommendations possibly diverged, the panel conducted a formal evidence review to determine which recommended management approaches should be tailored to men.
Similarities and Differences for Women and Men
THE PANEL’S RECOMMENDATIONS that were similar to those for women included the use of gene-expression profile testing to guide adjuvant treatment decision-making, the use of primary surgery, the use of adjuvant radiation therapy, and the use of chemotherapy in the adjuvant and advanced/metastatic disease settings. Areas of differences for men included the use of endocrine therapy, the recommended use of routine genetic testing for inherited risk factors, survivorship care, and routine mammography for men treated with lumpectomy.
Sharon H. Giordano, MD, MPH, FASCO
“One of the main areas where our recommendations were different for men than for women was the use of tamoxifen as the adjuvant endocrine therapy of choice,” noted Sharon H. Giordano, MD, MPH, FASCO, of The University of Texas MD Anderson Cancer Center and Guideline Co-Chair. “Tamoxifen is underused in general, and there’s also been some controversy about optimal endocrine therapy in men. In women—especially those who are postmenopausal—there is a tendency to use aromatase inhibitors rather than tamoxifen, so our recommendation clarified that, for men, we really should use tamoxifen rather than start with aromatase inhibitors,” she said.
Recommendations were adopted when they reached at least 75% consensus among the panel members. Areas that did not meet that threshold—including the issue of surveillance after breast cancer diagnosis and whether every male survivor should undergo routine screening mammograms—may be revisited in the future, pending more data.
Shaping Research and Practice
THE RECOMMENDATIONS are designed for oncologists to immediately implement into practice, but the hope is that the guideline will help stimulate research initiatives as well. “Some research studies in breast cancer enroll only women. We should try to get away from women-only studies,” Dr. Hassett explained. “I hope that the commonalities between men and women that we highlight in the guideline will reinforce the idea that, if we are doing a clinical trial in breast cancer, it should typically include both women and men, unless the treatment involves an aspect of endocrine treatment only relevant to women.”
Such trials are imperative for generating the much-needed data upon which formal practice guidelines are often based. However, Drs. Hassett and Giordano both emphasized that there always may be populations or aspects of care for which the field lacks evidence. Thus, consensus-based recommendations should be viewed in the context of this limitation and considered the best the field has to offer at any given time.
“I think the guideline will be useful, because so many oncologists don’t see many male [patients with] breast cancer. However, we have limited data to work from,” Dr. Giordano cautioned.
“There is always room for guidelines to improve, and they are often driven by opinion when you don’t have the evidence base,” continued Dr. Giordano. “I think this guideline represents the best we have right now. And, hopefully, we will generate data from larger studies, which will give us that evidence base in the future.”
DISCLOSURE: Drs. Hassett and Giordano reported no conflicts of interest.
1. National Cancer Institute Surveillance, Epidemiology, and End Results Program: Cancer stat facts: Common cancer sites. Available at https://seer.cancer.gov/statfacts/html/common.html. Accessed March 3, 2020.
2. Hassett MJ, Somerfield MR, Baker ER, et al: Management of male breast cancer: ASCO guideline. J Clin Oncol. February 14, 2020 (early release online).
Originally published in ASCO Daily News. © American Society of Clinical Oncology. ASCO Daily News, February 20, 2020. All rights reserved.