Retrospective Study to Determine Factors Influencing Outcome in Patients With Human Epidermal Growth Factor Receptor 2-Positive Breast Cancer Receiving Neoadjuvant Chemotherapy.

Purpose: There are scant data on patients with human epidermal growth factor receptor 2 (HER2)-positive breast cancer treated with neoadjuvant therapy (NAT) in real-world settings with limited access to HER2-targeted therapy.

Methods: This was a retrospective analysis of patients with nonmetastatic, HER2-positive breast cancer treated with NAT between January 2014 and December 2018 to determine factors affecting pathologic complete response (pCR), event-free survival (EFS), and overall survival (OS).

Results: The cohort comprised 1,004 patients with a median age of 47 years, 533 (53.1%) with clinical T3/T4 tumors, 466 (46.4%) with clinical N2/3 status, and 527 (52.5%) with hormone receptor-positive disease. Trastuzumab was given to 528 (52.6%) patients in the neoadjuvant setting and 711 (70.8%) patients in neoadjuvant and/or postoperative settings. pCR was achieved in 226 (22.5%) patients; the 5-year EFS in the whole cohort, pCR group, and no-pCR group was 63.5% (95% CI, 60.36 to 66.63), 86.1% (95% CI, 81.59 to 90.60), and 57% ([95% CI, 53.47 to 60.52]; P < .001), respectively. In multivariable analysis in the full cohort, smaller tumor size (cT1/T2 v cT3/T4), higher grade (III v II), hormone receptor-negative status, and use of neoadjuvant HER2-targeted therapy were significantly associated with higher pCR, and smaller tumor size (cT1/T2 v cT3/T4), lower node involvement (cN0/N1 v cN2/N3), achievement of pCR, and receiving trastuzumab were significantly associated with higher EFS and OS.

Conclusion: In a setting with constrained access to HER2-targeted therapy, lower clinical tumor burden and receiving trastuzumab were significantly associated with increased pCR and survival in patients with HER2-positive breast cancer treated with NAT. Efforts should be made to enhance early diagnosis and access to HER2-targeted therapy worldwide.