ESTRO 2022 - Abstract Book

S1677

Abstract book

ESTRO 2022

G.E.F. Noubbigh 1 , M. Frikha 2 , S. EL Alami 2 , S. Yahyaoui 2 , S. Zaraa 2 , A. Yousfi 2 , A. Mousli 2 , R. Abidi 2 , I. Saidani 2 , M. Mahdhouani 3 , K. Mahjoubi 2 , C. Nasr 2 1 institut salah azaeiz, Radiotherapy, Tunis, Tunisia; 2 institut salah azaeiz, Radiotherapy , Tunis, Tunisia; 3 institut salah azaeiz, Radiotherapy , Tunis, Tunisia Purpose or Objective The toxicity of the post-operative radiotherapy of gastric cancer remains one of the major concerns in practice because of the organ proximity and their great mobility in the abdominal cavity. As the pancreas has both an exocrine and endocrine function, these capacities could be loosed after abdominal irradiation with a significant risk of malabsorption syndrome, diabetes or pancreatitis. However, the pancreas is not yet considered as an organ at risk and there are few reports in the literature that published the relationship dose-effect to establish dose constraints for planning. The purpose of our study is to analysis the absorbed dose by pancreas during gastric cancer radiotherapy. Materials and Methods This is a retrospective study analyzing the dosimetric plans of all patients treated with postoperative radiotherapy for gastric cancer between 2015 and 2020 at the Salah Azaeiz Institute according to the MacDonald protocol. The dose was 45Gy for R0 and 50.4 Gy for R1. The treatment plan was performed with 3D conformal technique with two opposite anterior- posterior beams and two lateral beams. The pancreas was delineated according to RTOG recommendations. We recorded the pancreas Volume, mean dose (Dmean), the maximum dose (Dmax), the minimum dose (Dmin) from the dose-volume histogram. The data analysis was done by SPSS version 20. Results Thirty patients were included. Ninety three percent of the patients undergone 45 Gy in 25 fractions. The median of pancreatic volume was 31 cm 3[15-63]. The median of Dmoy, Dmax, Dmin were respectively 44.95 Gy [36-51.28], 47Gy [42-53.8], 43Gy [2.6-49.87]

The 3rd quartile (Q3) of Dmoy, Dmax, Dmin were respectively 45.65Gy , 47.9Gy and 44 Gy The following table summarizes the results of the dosimectric data for the panacreatic analysis: volume(cm3) Dmoy(Gy) Dmax(Gy) Dmin(Gy) Mean 31 44.95 47 43 Minimuim 15 36 42 2.6 Maximuim 63 51.28 53.8 49.87 Q3 41 45.62 47.9 44

Conclusion According to some studies, the pancreas could be considered as the salivary gland of the gastrointestinal tract. Doses to the pancreas in abdominal irradiations have been reported to be more than 30 Gy, which agreed with our study. However, according to a recent study published in 2018, the average doses to the pancreas should not exceed 20-25 Gy for preservation of its exocrine function and 25 Gy in the tail for preservation of its endocrine function. However, these results should be confirmed by larger series. Until then, why not propose systematic delineation of the pancreas during abdominal irradiation?