CLINICAL IMPACT OF ADJUVANT RADIOTHERAPY DELAY AFTER NEOADJUVANT CHEMOTHERAPY IN LOCALLY ADVANCED BREAST CANCER

SILVA, S.B. (ICESP (Instituto do Câncer do Estado de São Paulo)), PEREIRA, A.A.L. (ICESP (Instituto do Câncer do Estado de São Paulo)), MARTA, G.N. (ICESP (Instituto do Câncer do Estado de São Paulo)), LIMA, K.M.L.B. (ICESP (Instituto do Câncer do Estado

ICESP (Instituto do Câncer do Estado de São Paulo)Post-operative radiotherapy (PORT) is usually indicated for patients with breast cancer (BC) after neoadjuvant chemotherapy (NAC) and surgery. However, the optimal time to initiation of PORT is unknown.We retrospectively evaluated data from patients with non-metastatic BC who received PORT after NAC and surgery at our institution from 2008 to 2014. Patients were categorized into three groups according to the time between surgery and PORT: 16 weeks. The primary endpoint was disease free survival (DFS). The second endpoint was overall survival (OS). Multivariate Cox regression adjusted for molecular profile, histological grade (HG), age, clinical stage and complete pathologic response (pCR) was used to estimate survivals outcomes. Binary logistic regression model was used to calculate the adjusted odds ratios for recurrence.Of 581 patients included; most of them had clinical stage III (74%) and received anthracycline-taxane based NAC (95%). Forty-three patients received PORT within 8 weeks, 354 in 8-16 weeks and 184 beyond16 weeks from surgery. With a median follow-up of 32 months, initiation of radiotherapy up to 8 weeks after surgery was associated with better DFS (HR 0.36; 95%CI 0.146-0.914; p=0.03) and with a trend toward better OS (HR 0.223; 95%CI 0.07-1.14; p=0.08).PORT started up to 8 weeks after surgery was associated with better DFS in locally-advanced BC patients submitted to NAC. Our findings suggest that early initiation of PORT is critically important for these patients.

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