Surgical management in HER2 + de novo metastatic breast cancer: disease progression and survival.

PURPOSE: Advancements in human epidermal growth factor (HER)-targeted therapy have significantly improved survival in patients with de novo metastatic HER-2 positive (HER2+) breast cancer (dnMBC). The role of breast surgery is debated. We examined which HER2 + dnMBC patients undergo surgery and compared outcomes to systemic therapy alone.

METHODS

We performed a single institution retrospective review of patients with HER2 + dnMBC diagnosed 2011-2023. Data included demographics, clinicopathologic details, treatment information, local and distant disease progression, and survival outcomes. Analyses included logistic regression, Kaplan Meier, and Cox proportional hazards models.

RESULTS

The study included 103 patients. Of these, 42.7% underwent breast surgery (70.5% mastectomy, 29.5% lumpectomy). Of these, 72.7% underwent axillary surgery (38.6% axillary lymph node dissection, 27.3% sentinel lymph node biopsy, 6.8% targeted axillary dissection). The median age at diagnosis was 48 years (surgery) and 56 years (no surgery) (p = 0.10). The surgery group had lower number of metastatic sites (1.3 vs. 1.9, p = 0.003) and exhibited higher rates of local disease progression pre-operatively (39% vs. 23.5%, p = 0.05). Post-operatively, there was no significant difference in local disease progression (17.1% vs. 23.5%, p = 0.42). After adjusting for age, sites of metastases, and number of metastatic sites, those who underwent surgery had improved overall survival (HR 0.33 (0.14-0.77), p = 0.02).

CONCLUSION

Patients with HER2 + dnMBC with lower metastatic disease burden and local disease progression were more likely to undergo breast surgery. There was no significant difference in local disease control post-operatively. The significant association between surgery and improved survival must be interpreted with caution due selection bias in this retrospective study.