ESTRO 2024 - Abstract Book

S720

Clinical - Breast

ESTRO 2024

3171

Digital Poster

Breast Cancer Radiotherapy after Neoadjuvant Systemic Therapy: a retrospective evaluation

Marzia borgia 1 , Maria Chiara De Luca 1 , Roberta Castagna 1 , Maria Carmen Francavilla 1 , Tiziana Proto 1 , Alessandra Castelluccia 1 , Alessandra Sallustio 1 , Ester Sanfilippo 1 , elisa valzano 1 , Federica Tanzarella 1 , Laura Orlando 2 , Mariangela Pasqualoni 2 , Antonella Bodini 3 , Maurizio Portaluri 1 , Francesco Tramacere 1 1 A. Perrino Hospital, Radiation Oncology Unit, Brindisi, Italy. 2 A. Perrino Hospital, Oncology Unit, Brindisi, Italy. 3 National Research Council, Institute for Applied Mathematics and Information Technologies "E. Magenes", Milan, Italy

Purpose/Objective:

Neoadjuvant chemotherapy (NAC) is increasingly used in selected high-risk, locally advanced breast cancer (BC) patients in order to downstage the primary tumor in the breast and the metastatic axillary lymph node, often resulting in a small increase in breast conservation rates. The increasing use of NAC in BC has resulted in treatment issues for radiation oncologists, caused by few literature experiences in this setting of patients. Furthermore, the value of pathologic complete response (pCR) after NAC and also of the time from surgery to Radiotherapy (RT) is not established. The aim of this study is to evaluate clinical outcomes in terms of overall survival (OS), disease free survival (DFS) and loco-regional recurrence (LRR) and to assess value of pCR and of the time from surgery to RT on patients undergoing NAC.

Material/Methods:

We retrospectively analyzed BC patients treated in our RT Unit. All patients underwent NAC followed by breast conserving surgery (BCS) or mastectomy. Whole breast RT with or without supraclavicular lymph node RT was performed. Clinical outcomes, as LRR, DFS and OS, were analyzed, measured from surgery until first event.We analyzed all time to-event distributions using the Kaplan – Meier method to calculate the DFS and OS rates at 5 years. RTOG scales were used for acute RT toxicity evaluation. pCR was defined as the absence of residual invasive disease in the breast and lymph nodes.The time to start of RT was calculated as the interval between the date of surgery and the first day of RT obtaining 2 group: patients undergoing RT until and after 4 months.

Results:

One-hundred and ten advanced BC patients undergoing NAC and treated between 2014 and 2020 were retrospectively analyzed. The median age was 51 years (range=29-80). Patients, tumor and treatment characteristics are summarized in Table 1. NAC was prescribed according to staging and tumor biology. After NAC, 42% of patients underwent BCS, while 58% underwent mastectomy; axillary dissection was performed in 64% of patients. All patients underwent adjuvant RT: conventional fractionation was chosen in 24%, while in 76% a moderate hypofractionation was used (total dose 4005 or 4256 cGy); 73% of patients underwent supraclavicular lymph node RT. The Kaplan-Meyer estimates of 5-years OS and DFS were 78% and 73% respectively (Figure 1). Loco-regional recurrence occurred in 6 patients (6%): of them, 4 patients (67%) had a breast relapse and 2 patients (33%) had an