ESTRO 2021 Abstract Book

S1034

ESTRO 2021

PO-1253 Influence of radiation treatment technique on outcome and toxicity in anal cancer. M.C. Fernandez Fernandez 1 1 hospital Virgen Del Rocío, Radiotherapic Oncology, Seville, Spain Purpose or Objective Objective : Chemoradiation for anal cancer yields effective tumour control but it is associated with significant acute toxicity. We compared outcomes and toxicity with concurrent and simultaneous integrated boost- volumetric arcotherapy with modulated intensity (SIB-VMAT) vs. three-dimensional conformal radiation (3D- Methods : We study 45 diagnosed patients,12 of them in biopsy-proven stage II ,13 in stage IIIA and 20 in stage IIIB of squamous–cell carcinoma of the anal cancer. They were treated with SIB-VMAT (20 patients) and 3D-CRT (25 patients), as part of definitive Mitomycin-C/5-fluorouricil-based chemoradiation from 2005 a 2020.The patients treated with 3D-CRT received a total dose of 59,4 Gy delivered to the primary tumour and macroscopically involved lymph nodes and 45 Gy to elective lymph nodes areas in 33 fractions. The patients treated SIB-VMAT received a total dose de 59,4 Gy in the primary tumour and macroscopically involved lymph nodes and 50,4 Gy in elective lymph nodes areas in 28 fractions. Results Results : The mean age of the patients was 56,3 years, 55% of patients were females and 26,6% were human immunodeficiency virus-positive ones. Acute grade 3+ dermatologic toxicity appeared in 64% of patients in the group 3D-CRT and 20% in the group SIB-VMAT; of grade 2+, 20% in 3D-CRT and 45% in SIB-VMA; pain, 4% in group 3D-CRT; gastrointestinal grade I, 5% in SIB-VMAT and grade II, 5% in SIB-VMAT and 8% in 3D-CRT. Our goal is to determine if the treatment to be applied does not produce significant differences between the various side effects that it can cause. We have considered two treatments, which are Group 1 with the SIB- VAMT technique and Group 2 with the 3D-CRT Technique As the two variables (Groups and Effects) are encoded as ordinal, the non-parametric test of two independent samples (Mann-Whitney test) has been applied. The significance level set is 1% (α-0.01). Achieved results . It is observed that there are significant differences between the two treatment groups, since the p-value of the test is less than the significance level (0.004<0.01). Based on a contingency table, we observe that the most severe effects are produced by 3D-CRT treatment. In fact, 48.89% of treated patients with 3D-CRT treatment end up suffering from grade II or III dermatitis, while this percentage is reduced to 28.89% with SIB-VMAT treatment The overall survival (Kaplan-Meier) was 51,9% to 109 months. The actuarial overall survival in the group 3D- CRT to 109 months was 59% (SD 11%) and to 66 months was 68% (SD 11%). In group of SIB-VMAT to 66 months was 71,8% (SD 11%). There are not significant differences between the two treatment groups with p=0.092 by using the logrank test Conclusion Conclusion : SIB-VMAT and concurrent chemotherapy significantly reduced acute toxicities and seems to be safe and feasible with oncological outcomes in anal cancer patients CRT) for anal cancer. Materials and Methods 1 hospital And University Of Bordeaux, Radiation Oncology, Bordeaux, France; 2 haut-Lévêque Hospital, University Of Bordeaux, Colorectal Surgery, Pessac, France; 3 haut-Lévêque Hospital, University Of Bordeaux, Colorectal Surgery, Pessac, France; 4 Haut-Lévêque Hospital, University of Bordeaux, Radiology, PESSAC, France; 5 Haut-Lévêque Hospital, Colorectal surgery, PESSAC, France Purpose or Objective To assess the feasibility of a watch and wait strategy after neoadjuvant treatment for rectal adenocarcinoma. Materials and Methods Patients not eligible for organ preservation trials with local excision (anal sphincter infiltration, >4 cm or not eligible for chemotherapy) were included. Patients with good response at 6 weeks after radiotherapy (MRI : 50% downsizing or TRG1-3) were reassessed at 12 weeks. Complete clinical responders (no visible or palpable mass at digital rectal examination /rectoscopy and MRI major fibrosis TRG1-2) were monitored every 4 Fifty patients (male : 30, female : 20), median age 67 years (range : 37-89), were included from 2016 to 2020. Rectal tumors were initially classified as T2 (n=13), T3 (n=28) T4 (n=9); N1 (n=21). Median distance from anal margin was 3.5 cm (range 0-8). Neoadjuvant treatment consisted of chemoradiotherapy after induction chemotherapy (Folfirinox/4 cycles) in 19 cases. Median follow-up was 22 months (range 4-50). Nine patients (18%) experienced local regrowth and 2 metastatic evolution. Local recurrences were treated by local excision (n=4), Total Mesorectal Excision (n=4) or abstention (n=1). Rectal preservation rate was 92% (46/50) and overall survival was 94% at 3 years. Conclusion In case of clinical complete response after neoadjuvant treatment, Watch-and-Wait strategy allows for rectal preservation in the majority of cases. This strategy could be beneficial especially for low rectal tumors. months. Results PO-1254 Watch and wait strategy for rectal cancer : preliminary results V. Vendrely 1 , M. Boubaddi 2 , T. Cauvin 3 , N. Frulio 4 , Q. Denost 3 , E. Rullier 5

PO-1255 prospective study of safety and response in moderately hypofractionated chemoradiation rectal cancer D. G R 1 , H. Nair 2 , R. Madhavan 1 , D. Dutta 2