The Role of Radiotherapy for Patients with Unresectable Locally Advanced Breast Cancer following Neoadjuvant Systemic Therapy

BACKGROUND: For locally advanced breast cancer (LABC) patients who remained unresectable after neoadjuvant systemic therapy (NST), radiotherapy (RT) is considered as an approach for tumor downstaging. In this study, we attempted to discuss the value of RT for patients with unresectable or progressive disease in the breast and/or regional nodes following NST. METHODS: Between January 2013 and November 2020, the data for 71 patients with chemo-refractory LABC or de novo bone-only metastasis stage IV BC who received locoregional RT with or without surgical resection were retrospectively analyzed. Factors associated with tumor complete response (CR) were recognized using logistic regression. Locoregional progression-free survival (LRPFS) and progression-free survival (PFS) were calculated using the Kaplan–Meier method. The Cox regression model was applied to recognize the recurrence risk factors. RESULTS: After RT, 11 patients (15.5%) achieved total cCR. Triple-negative subtype (TNBC) was associated with a lower total cCR rate compared with other subtypes (p = 0.033). 26 patients proceeded to surgery, and the operability rate was 36.6%. 1-year LRPFS and PFS were 79.0% and 58.0%, respectively, for the entire cohort. Surgical cases had an improved 1-year LRPFS (p = 0.015), but not 1-year PFS (p = 0.057), compared with definitive RT cases. Non-any cCR was the most prominent predictor of a shorter LRPFS (p < 0.001) and PFS (p = 0.002) in the multivariate analysis. Higher TNM stage showed a trend toward a shorter LRPFS time (p = 0.058), and TNBC (p = 0.061) showed a trend toward a shorter PFS interval. CONCLUSIONS: This study demonstrated that RT was an effective tumor downstaging option for chemo-refractory LABC. For patients with favorable tumor regression, surgery following RT might bring survival benefits.