Recurrence rates in patients with HER2+ breast cancer who achieved a pathological complete response after neoadjuvant pertuzumab plus trastuzumab followed by adjuvant trastuzumab: a real-world evidence study

Purpose This study assessed real-world risk of invasive disease recurrence (IDR) and associated factors in patients with human epidermal growth factor receptor-2 positive (HER2+) early breast cancer (BC) with pathological complete responses (pCR) after neoadjuvant pertuzumab plus trastuzumab (nPT) plus chemotherapy, followed by adjuvant trastuzumab (aT). Methods Patients with HER2+ BC with pCR after nPT from 2013 to 2015 who received aT were identified in the US Oncology Network and followed until IDR or censoring. Kaplan–Meier and Cox regression methods were used to assess invasive disease-free survival (iDFS) and correlation between iDFS and patient characteristics. Results A total of 217 pCR patients’ charts were reviewed; median age was 52 years. Most had stage IIA or IIB disease (62%), Eastern Cooperative Oncology Group performance status (ECOG PS) ≤ 1 (84%), tumor size > 2 cm (75%), positive nodes (N+, 62%) and negative estrogen and progesterone receptor (ER− and PR−) expression (52%). Four-year iDFS rates were 90.0% overall (95% CI 84.6%, 93.6%), 86.2% for the N+ cohort and 96.0% for the N− cohort. Cox regression suggested that age, body mass index, ECOG PS, N+ status, stage T3 or T4, and ER+ or PR+ status were risk factors for IDR but were not statistically significant. Conclusions Consistent with previous studies, this real-world study observed that patients with HER2+ BC showing pCR with nPT remain at risk for IDR, especially with node-positive disease at diagnosis. Alternatives to adjuvant trastuzumab alone, including combined trastuzumab and pertuzumab, should be considered to improve outcomes for initially N+ patients showing pCR with nPT.