ESTRO 2020 Abstract book

S623 ESTRO 2020

PO-1088 Short Course Radiationtherapy chemotherapy and delayed surgery in locally advanced rectal carcinoma S. Mitra 1 , S. Aggarwal 2 , A. Dewan 3 , I. Kaur Wahi 2 , S. Barik 4 , K. Dobriyal 5 , J. Mukhee 5 , A. Jajodia 6 , H. Khurana 7 , A.K. Dewan 8 1 Rajiv Gandhi Cancer Institute & Research Centre, Senior Consultant Radiation Oncologist, Rohini- Delhi, India ; 2 Rajiv Gandhi Cancer Institute & Research Centre, Attending Consultant Radiation Oncologist, Rohini- Delhi, India ; 3 Rajiv Gandhi Cancer Institute & Research Centre, Consultant Radiation Oncologist, Rohini- Delhi, India ; 4 Rajiv Gandhi Cancer Institute & Research Centre, Senior Radiation Oncologist, Rohini- Delhi, India ; 5 Rajiv Gandhi Cancer Institute & Research Centre, Resident Radiation Oncologist, Rohini- Delhi, India ; 6 Rajiv Gandhi Cancer Institute & Research Centre, Resident Radiologist, Rohini- Delhi, India ; 7 Rajiv Gandhi Cancer Institute & Research Centre, Research Radiation Oncology, Rohini- Delhi, India ; 8 Rajiv Gandhi Cancer Institute & Research Centre, Senior Consultant Surgical Oncologist, Rohini- Delhi, India Purpose or Objective Objective : Short Course RT (scRT) and chemotherapy followed by delayed surgery has been hypothesized to increase the pathological complete response (pCR), decrease distant failures and improve survival in locally advanced rectal cancer patients. Material and Methods Methods : This is a prospective non randomized study approved by the institutional review board. All enrolled patients who have undergone scRT from November 2018 till May 2019 were included in an intention to treat analysis. All scRT patients were planned by IMRT technique with daily single fraction to a dose of 25Gy/5fractions/5 days. These patients then received FOLFOX based chemotherapy for 4-6 cycles followed by surgery and adjuvant chemotherapy. T3/T4 tumors, including synchronous liver metastasis were included in the study. Radiological evaluation was done by PET MRI at baseline and after completion of chemotherapy prior to surgery. The primary endpoint is complete pathological response (cPR). Secondary endpoints are survival analysis and toxicity evaluation Results Out of 54 patients enrolled till November 2019, 30 patients were analyzed during the specified period. All patients completed scRT. 27% (8/30) were Metastatic (Liver) while 73% (22/30) were non metastatic. Local surgery was done in 22/30 patients, 3/8 in the metastatic group after hepatic resection and 19/22 in nonmetastatic group. In the metastatic cohort, 3 patients had progressive disease and 2 patients were lost to follow up. In nonmetastatic cohort, 1 patient refused surgery and 2 patients were lost to follow up. 12/22 had APR, 9/22 had LAR and 1/16 had total proctocolectomy (underlying ulcerative colitis). All patients achieved negative resection margins. AJCC pathological tumour regression grade (pTRG) was assessed: 7/22(32%) had pTRG 0 (Complete response), 10/22(45%) patients pTRG 1 (Moderate/significant response), 5/22(23%) had pTRG 2 (Minimal response). No patient had pTRG3 (Poor response). Five patients had node positivity in the surgical specimen which 80%(4/5) had a minimal response (TRG2). PNI positivity was found in 1/16 patients and it had a minimal response (TRG2). No patient had any break or any toxicity requiring admission during radiotherapy. GI toxicity was assessed in terms of diarrhea, pain abdomen (colitis), need for supportive care and admission. (Figure1). Grade 3 neutropenia was observed in 24% of patients while on chemotherapy. MRTRG, ADC values in MRI and SUV change in PET were also correlated with pTRG and pathological T staging but no parameter had a significant correlation in the number of subjects analyzed to date.

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N=304 0 Gastrointestinal Toxicity Grade 2 Grade 3 Grade 4 Diarrhea 7 10 0 Colitis 8 4 0 Conclusion Short course radiation therapy followed by adjuvant chemotherapy and a delayed surgery is a well tolerated and promising regimen with good pathological response rates. Long term results related to late effects and survival analysis are awaited. 13 4 PO-1089 Major and complete response after neoadjuvant treatment in rectal cancer: a retrospective analysis M. Giraffa 1 , G. Chiloiro 2 , E. Meldolesi 3 , B. Corvari 3 , C. Coco 4 , R. Persiani 4 , L. Sofo 4 , S. Alfieri 4 , B. Barbaro 2 , V. Valentini 2 , M.A. Gambacorta 2 1 Università Cattolica del Sacro Cuore, Dipartimento di Diagnostica per Immagini- Radioterapia Oncologica e Ematologia, Rome, Italy ; 2 Università Cattolica del Sacro Cuore, Fondazione Policlinico Universitario A.Gemelli IRCCS - Dipartimento di Diagnostica per Immagini- Radioterapia Oncologica e Ematologia, Rome, Italy ; 3 Fondazione Policlinico Universitario A.Gemelli IRCCS, Dipartimento di Diagnostica per immagini - Radioterapia Oncologica ed Ematologia, Rome, Italy ; 4 Università Cattolica del Sacro Cuore, Fondazione Policlinico Universitario A.Gemelli IRCCS - Dipartimento di Chirurgia, Rome, Italy Purpose or Objective The conservative approach in locally advanced rectal cancer (LARC) patients (pts) who obtain a complete (CR) or major response (MR) after neoadjuvant radiochemotherapy (nCRT) is increasingly common. The objective of this study is to report the mono-istututional experience to evaluate the impact of a conservative approach on disease control after 3 years of follow-up (FUP). Material and Methods We analyzed LARC pts who obtained MR or CR after nCRT. All pts underwent RT on total mesorectum and draining lymph nodes at 45 Gy in 1.8 Gy/fraction, while the tumor and the corresponding mesorectum received 55Gy in 2.2Gy/fraction, with a Simultaneous Integrated Boost technique. Concomitant chemotherapy (CT) included chronomodulated orally capecitabine or CAPOX schedule, depending on clinical stage. All pts underwent restaging at least at 6-8 weeks with digital rectal exploration (DRE), magnetic resonance imaging (MRI); rectoscopy was not mandatory. Surgery, if needed, was planned at least 10-12 weeks from the end of nCRT. In selected case of MR or CR an organ preservation approach was performed by LE or wait and see (W&S). In this selected cases a close FUP was performed with DRE and rectoscopy every 3 months and MRI every 6 months, for 2 years. In case of tumoral regrowth TME surgery was suggested. Results From January 2014 to December 2017, 61 LARC pts achieved a MR or CR at first restaging (Table 1). Only 15 (24.6%) pts underwent a second restaging at 12 th – 14 th weeks which confirmed a MR, CR and partial response in 12, 2 and 1 cases, respectively. Seventeen (27.9%) pts achieved a MR: 13 and 4 underwent TME and LE, respectively. Among these one patient with a