Clinical Outcomes in Patients with Early Stage Node-Negative HER2-Positive Breast Cancer Receiving Upfront Surgery or Neoadjuvant Systemic Therapy.

Background: HER2-positive breast cancer is traditionally treated with neoadjuvant systemic therapy (NST), but optimal treatment sequencing is less clear in patients with small tumors. We investigated clinicopathologic and oncologic outcomes in early stage HER2-positive breast cancer.

Patients and methods: An institutional database was queried to identify patients with cT1-2 (≤ 3 cm) N0M0, HER2-positive breast cancer treated from 2015 to 2020 and compared upfront surgery and NST cohorts. Logistic regression was performed to identify factors predicting upstaging. Survival outcomes by group were compared using log-rank tests.

Results: Of 256 patients identified, 170 (66.4%) received upfront surgery and 86 (33.6%) NST. The NST cohort was younger and had more cT2 and grade 3 tumors and negative sentinel nodes. There was no significant difference in type of breast surgery or receipt of axillary lymphadenectomy. After upfront surgery, 4 (2.4%) patients had upstaging to pT > 3 cm and 18 (10.6%) to pN1-3. No factors predicted upstaging. After NST, 47 (54.7%) achieved pathologic complete response and 3 (3.5%) had upstaging to ypN1-3 with older age (OR 1.08, p = 0.004) and hormone receptor-positive status (OR 7.07, p = 0.002) identified as predictors. At median follow-up of 3.55 years, 10 (3.9%) patients had recurrence and 5 (2.0%) patients died. There were no significant differences in oncologic outcomes between groups.

Conclusions: Patients with cT1-2 (≤ 3 cm)N0 HER2-positive breast cancer selected for NST have higher-risk disease. Low rates of pathologic upstaging were observed with no difference in surgical treatments and overall excellent oncologic outcomes in both groups. These findings may guide decision-making regarding treatment sequencing for patients with early stage HER2-positive disease.