The prognostic significance of metastatic pattern in stage IV male breast cancer at initial diagnosis: a population-based study.

Purpose: Metastatic pattern (MP) is a prognostic factor in women with breast cancer. However, the prognostic significance of MP in male breast cancer patients remains unknown.

Methods: Using the SEER database, we gathered demographic information and disease characteristics for men diagnosed with de novo metastatic breast cancer from 2010 to 2017. Metastases to bone, brain, liver, and lung were used to define MP (bone-only, visceral, bone and visceral [BV], or other). Statistical analyses were performed to identify associations between overall survival (OS) and MP, as well as other patient and tumor features. We used multivariate logistic regression to evaluate factors associated with sites of metastases.

Results: We included 250 patients. MP distribution was bone = 38.8%, visceral = 14.8%, BV = 33.2%, and other = 13.2%. Median OS for each was bone = 33 months, visceral = 23 months, BV = 20 months, and other = 46 months (p = 0.046). Patients with brain metastases had significantly shorter OS compared with no brain metastases (median OS = 9 months vs. 30 months; p < 0.001). Compared with other subtypes, triple negative had the shortest OS (median 9 months, p < 0.001). Logistic regression modeling revealed that compared with HR+/HER2- breast cancers, HR-/HER2+ had higher odds of liver metastases and triple negative had higher odds of brain metastases. Patients younger than 50 years had a significantly greater risk of developing brain metastases.

Conclusions: MP and tumor subtype can predict OS outcomes in men with metastatic breast cancer at diagnosis. Brain metastases confer very poor prognosis.