ESTRO 2020 Abstract book

S188 ESTRO 2020

OC-0330 Neoadjuvant breast radiotherapy for one stage mastectomy and autologous breast reconstruction M.W.T. Chao 1 , S. Jassal 2 , C. Baker 3 , M. Tacey 4 , M. Law 2 , S.W. Loh 5 , M. Cheng 2 , C. Yong 2 , N. Zantuck 2 , E. Bevington 5 , A. Hyett 5 , M. Guerrieri 1 , M. Cokelek 1 , B. Brown 6 , M. Chipman 7 , G. Chew 5 , B. Yeo 8 , J. Lippey 3 , D. Neoh 5 , G. Lamoury 9 , A. Spillane 10 , C. Foley 5 , P. Kechagioglou 11 , M. Rolfo 11 , F. Foroudi 4 1 Genesis Care Victoria, Ringwood Radiation Oncology Center, Melbourne, Australia ; 2 Maroondah Hospital, Surgical Oncology, Melbourne, Australia ; 3 St Vincent's Hospital, Breast Oncology, Melbourne, Australia ; 4 Olivia Newton John Cancer Center, Radiation Oncology, Melbourne, Australia ; 5 Olivia Newton John Cancer Center, Surgical Oncology, Melbourne, Australia ; 6 Frankston Hospital, Surgical Oncology, Melbourne, Australia ; 7 St Vincent's Hospital, Medical Oncology, Melbourne, Australia ; 8 Olivia Newton John Cancer Center, Medical Oncology, Melbourne, Australia ; 9 Royal North Shore Hospital, Radiation Oncology, Sydney, Australia ; 10 Royal North Shore Hospital, Surgical Oncology, Sydney, Australia ; 11 Genesis Care UK, Windsor Radiation Oncology Center, London, United Kingdom Purpose or Objective Delayed breast reconstructions are preferred for high risk/locally advanced breast cancer patients who require post mastectomy radiotherapy due to superior cosmetic and lower complication rates. However, the use of neoadjuvant radiotherapy (NART) prior to surgery allows for definitive oncological surgery to be performed with an immediate autologous breast reconstruction (ABR) in a single operation. The aim of this study is to review the oncological outcomes of pts who underwent NART. Material and Methods This is a multi-institutional prospective review of 147 pts who underwent NART with 149 evaluable breasts. All pts had initial chemotherapy, followed by NART (median dose 50.4 Gy in 28 fractions) to the breast, supraclavicular fossa and level 3 axilla. Approximately 6 weeks after completing NART, pts underwent definitive surgery and ABR. Results There were 117 clinically staged pts with 119 evaluable breasts (cStage 2A-3C) and 32 pathologically staged pts (pStage 2A-3C) with a median age of 47 years. The median follow- up from surgery was 1.7 years. Another 32 pts (pStage 2A-3C) were pathologically staged having had their initial wide local excision and axillary surgery but either required or chosed to have a mastectomy and reconstruction. All pts completed their NART with minimal toxicity and no break in radiotherapy delivery. 144 pts had a skin-sparing mastectomy and 5 pts had a modified radical mastectomy. A DIEP reconstruction was performed in the majority of pts (84.6%). The median length of hospitalisation was 6 days (Inter-quartile range 5 to 7 days). Of the 119 clinically staged breasts, 77.3% achieved Miller- Payne downstaging of 4-5/5. Her2 positive phenotype achieved a MP score of 5/5 in 81.5%. The risk of developing any acute breast complication in the entire cohort was 23.4% (grade 3 9%) with no flap failures. The risk of developing any acute donor site complication was 16.8% (grade 3 6%). The risk of developing any acute breast or donor site complications was 33.6% (grade 3 12.1%). The risk of developing longer term toxicities such as flap contracture and fat necrosis is 2% and 12.1% respectively. The majority of patients (98%) rated their reconstruction as good to excellent. Local recurrence was observed in 2

breasts, distant metastatic progression in 16 patients with 7 deaths over the follow-up period. Conclusion This review demonstrated that NART is a safe technique, which has not lead to an increase in surgical complication rates. SR can achieve a shorter, simpler reconstructive journey for patients.

Proffered Papers: Proffered papers 17: GI

OC-0331 Excellent antitumor activity of SBRT and FOLFIRINOX in patients with pancreatic cancer J. Nuyttens 1 , M. Suker 2 , F. Eskens 3 , C. Van Eijck 2 1 Erasmus MC Cancer Institute, Radiation oncology, Rotterdam, The Netherlands ; 2 Erasmus Mc, Surgery, Rotterdam, The Netherlands ; 3 Erasmus MC, oncology, Rotterdam, The Netherlands Purpose or Objective Patients with locally advanced pancreatic cancer (LAPC) benefit from a standardized treatment regimen of systemic therapy followed by local therapy. We conducted a multicenter phase II trial to investigate feasibility and antitumor activity of sequential FOLFIRINOX and Stereotactic Body Radiotherapy (SBRT) in patients with LAPC (LAPC-1 trial). Material and Methods A single-arm, open-label multicenter phase 2 trial. Patients with biopsy-proven LAPC treated in four hospitals in the Netherlands between December 2014 and June 2017. Inclusion criteria consisted of World Health Organization performance status 0-1 and adequate hematologic, renal, and hepatic function. All patients underwent a staging laparoscopy prior to treatment and a restaging CT-scan after FOLFIRINOX was finished prior to SBRT. Patients were followed with CT scans to consider potential resectability. Patients received 8 cycles of FOLFIRINOX followed by SBRT (5 fractions of 8Gy) if no tumor progression after the FOLFIRINOX treatment was observed. Following SBRT, resection was considered in case tumor downstaging was seen on restaging CT scans. Results Fifty patients were included and did start with FOLFIRINOX treatment. Thirty-nine (78%) patients were not progressive under chemotherapy and were treated with SBRT. The 3-years overall survival and the median OS for patients who had finished SBRT was 13% and 17 months (95% CI 14-21) and was 7 months (95% CI 6-8) in patients who had not received SBRT (p<0.001). Six (12%) patients underwent exploratory laparotomy, all resulting in a complete (R0) resection. Two patients had a complete pathological response. The median OS for the six patients that underwent resection was 23 months (95% CI 13-34). Two (5%) grade 3 or 4 adverse events after SBRT were observed. Two (5%) grade 5 adverse events consisting of gastro-intestinal bleeding within three months after SBRT were observed. Conclusion FOLFIRINOX followed by SBRT in patients with LAPC shows excellent antitumor activity with a 3-years overall survival of 13%. In 6 (12%) patients a potentially curative resection could be pursued following this combined treatment, with a complete histological response being observed in two patients.

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