Characteristics, treatment and outcomes of HER2 positive male breast cancer.

Background: Research describing male breast cancer with HER2 overexpression is limited. This study evaluated the characteristics, treatment, and outcomes of HER2 positive breast cancer in men.

Methods: Information for January 2010 through December 2017 was obtained from the SEER Research Plus database.

Results: Four hundred sixty-two men were HER2 positive (13%) of 3594 cases of breast cancer. Compared to HER2 negative patients, these patients were younger at diagnosis (63 vs. 67 years, p < 0.001), had more poorly differentiated cancer (Grade III 53% vs. 33%, p < 0.001), and larger tumor size (28.8 vs. 24.6 mm, p < 0.001). HER2 positive males also had distant site and/or contralateral lymph node involvement more often (13% vs. 7%, p < 0.001), had higher rate of cancer-related mortality (15% vs. 10%, p = 0.002), and shorter overall survival (34 vs. 38 months, p = 0.004).

Conclusion: Men diagnosed with HER2 positive breast cancer had more advanced disease at diagnosis and worse outcomes than HER2 negative men despite increased utilization of systemic therapy.