Clinical Course of Breast Cancer Patients with Local-Regional Progression During Neoadjuvant Systemic Therapy.

Neoadjuvant systemic therapy (NST) is standard for locally advanced breast cancer and is now frequently considered for those with early-stage and node-positive disease. We aimed to evaluate the treatment course and outcomes in patients with disease progression during NST. Patients diagnosed with unilateral stage I–III breast cancer between 2005 and 2015 with documented local-regional progression while receiving NST, by clinical examination and/or imaging after two or more cycles of chemotherapy, were identified from a prospective database, stratified by receipt of surgery and outcomes analyzed. Of 6362 patients treated with NST during the study period, 124 (1.9%) developed disease progression. At a median live follow-up of 71 months, 23.4% were alive without disease and 70.2% had died from breast cancer. Median overall survival (OS) time for patients with progression was 26 months and median distant disease-free survival (DFS) was 14 months. Triple-negative breast cancer was associated with a higher likelihood of death (p < 0.001) and development of distant metastasis (p = 0.002). Among patients who had surgery (104, 89.3%), 40 (38.5%) developed local-regional recurrence, 67 (64.4%) developed distant metastasis, and 69 (66.3%) died from breast cancer. Median OS and median distant DFS in this subgroup was 31 and 16 months, respectively. High rates of local-regional and distant failure were seen following disease progression while receiving NST. This suggests aggressive tumor biology and the need to study novel systemic therapies. Poor survival outcomes despite surgical management highlight the importance of careful patient selection when considering operative intervention after progression while receiving NST.