ESTRO 2023 - Abstract Book

S934

Digital Posters

ESTRO 2023

CR/PR with no evidence of distant disease on review at 1 & 4 years post-LDRT. 50% (3/6) had distant PD. 12% (1/6) was lost to follow up after 1 year, having achieved CR. At a median follow-up of 4.7 years, 5-yr LPFS was 71% and OS 80%. Conclusion LDRT for indolent lymphoma involving the orbit(s) offers high response rates & durable effect. We propose that in such cases, LDRT is an attractive initial option compared to the standard 24Gy/12#. Given distant relapse rates, the more durable responses reported with 24Gy/12# may not be of clinical significance. However, further work on relapse rates & patterns in those presenting with orbital disease only is warranted.

PO-1168 Total body irradiation (TBI) by helical Tomotherapy- single institution experience from India.

A.G. Gopal 1 , D.K. Gudipudi 2 , H. Kauser 1 , R. Nabariya 1 , G. P 3 , V.K. S 1 , S. Gunda 4 , K.R. Alluri 1 , V.C. Patil 4 , P.K. B 4 , N.V.N.M. Stesty 5 1 Basavatarakam Indo American cancer hospital and research Institute, Radiation Oncology , Hyderabad , India; 2 Basavatarakam Indo American cancer hospital and research Institute, Radiation Oncology, Hyderabad, India; 3 Basavatarakam Indo American cancer hospital and research Institute, Radiation Oncology , Hyderabad, India; 4 Basavatarakam Indo American cancer hospital and research Institute, Radiation Oncology, Hyderabad , India; 5 Basavatarakam Indo American cancer hospital and research institute, Medical physics, Hyderabad , India Purpose or Objective With the installation of Tomotherapy in our institute in 2017, we present a cohort of patients who underwent TBI for Haematopoitic stem scell transplant (HSCT) at our institute. We present radiation planning details, dosimetry data and acute toxicity. Materials and Methods Between November 2017 and October 2022, a cohort of 50 patients underwent TBI on TomoTherapy. A dose of 2 Gy to 12 Gy delivered in 1 to 6 fractions over 1 to 3 days with minimum of 6-8hours gap between fractions. Patients were immobilized in supine position with a body-vac lock and 3-clamp open face head mask and planning computed tomography scans were done from vertex to toes and for patients >135cms, an upper scan(vertex to knee joint) and a lower scan(toes to pelvis). Planning target volumes (PTV) were created with an inner margin of 2 mm and outer margins of 10 and15 mm around the body contour. Lungs were contoured with an inner margin of 5 and 10 mm to account for respiration. The planning parameters used consisted of a jaw width of 5cm for all the cases, a pitch that ranged from .39 to.43 and a modulation factor ranging from 2.3 to 1.47. We collected the doses to target volume, lungs, and dose homogeneity index RTOG (DHI) of these patients. Results The median age was 19 years (range 4-61), 28/50 (56 %) males and 22/50 (44%) females. Treatment with a single scan was possible in 8/50 (16%) and 2 scans 42/50(84%). The most common diagnosis was Acute Lymphoblastic Leukaemia (ALL)(66%) followed by aplastic anaemia 24%, lymphoma 6% and others like Fanconi anaemia and red cell aplasia each 1 case(4%). There were 16 cases of ALL who were planned for 12 Gy radiation (32%), 15 patients who received 2 Gy (30%), 6 patients received 8 Gy (12%), 5 patients received 6 Gy (10%), 3 patients each for 10 Gy, 3 Gy and 4Gy (6%). Median Beam on time (BOT) is 28 min, range (36-13), median 95 % PTV coverage is 96 %, range (98-93), median DHI is 1.28 range (1.52- 1.02). Subset analysis of cohort planned for 12 Gy had median 95 % PTV received 96 % dose , that is 11.5 Gy, median Dmax to PTV is 14.67, range is15.87-11.95, median Dmean to PTV is 11.4 Gy range is12.62- 2.54, median DHI is 1.3 ,range 1.39- 1.16, median BOT is 27.21 minutes, range34.19-14.9, median lung Dmax is 12.6Gy, range13.6-10.33,median lung Dmin is 8.02 Gy, range 10.15 – 7.22,median Lung Dmean is 10.39, range 0.97-9.11. Fatigue, nausea and vomiting were the most common acute toxicities and none required cessation of radiation treatment. One patient developed grade 2 skin reaction at 10Gy and the last fraction was omitted. Conclusion Our experience with TBI using helical Tomotherapy shows that it is convenient and acceptable with an adequate dose coverage, with homogenous distribution and to limit the dose to critical organs. F. Mammini 1,2 , I. Ammendolia 1 , E. Deraco 1,3 , L. Cavallini 4,5 , F. Medici 3,4 , G. Cicoria 6 , S. Strolin 6 , G. Paolani 6 , M. Santoro 6 , L. Strigari 6 , A.G. Morganti 7,3 , S. Cammelli 7,3 1 ircss Azienda Ospedaliero-Universitaria di Bologna, Radiation Oncology, bologna, Italy; 2 Alma Mater Studiorum University of Bologna, Department of Experimental, Diagnostic and Specialty Medicine-dimes, bologna, Italy; 3 Alma Mater Studiorum University of Bologna, Diagnostic and Specialty Medicine-dimes, bologna, Italy; 4 IRCSS Azienda Ospedaliero-Universitaria di Bologna, Radiation Oncology, bologna, Italy; 5 Alma Mater Studiorum University of Bologna, Diagnostic and Specialty Medicine-dimes, Bologna, Italy; 6 IRCCS Azienda Ospedaliero-Universitaria di Bologna, Medical Physics Unit, bologna, Italy; 7 IRCCS Azienda Ospedaliero-Universitaria di Bologna, Radiation Oncology, bologna, Italy Purpose or Objective Total body irradiation (TBI) can be part of the conditioning regimen for patients with leukemia undergoing hematopoietic stem cell transplantation. PO-1169 Volumetric modulated arc therapy based Total Body Irradiation (TBI): a single center experience