ESTRO 2023 - Abstract Book

S796

Monday 15 May 2023

ESTRO 2023

The VorteX (NCT00423618) phase III trial studied whether a reduction in radiotherapy treatment volumes reduced normal tissue toxicity for soft tissue sarcoma of the extremities (STSE) treated with adjuvant radiotherapy to 66 Gy. The IMRiS (NCT02520128) phase II trial studied the feasibility of Intensity-Modulated Radiotherapy (IMRT) in the neo-adjuvant (50 Gy) and adjuvant (60 Gy) settings. This work compares toxicities reported for both trials. Materials and Methods Descriptive statistics were calculated for maximum RTOG and Stern scale toxicities occurring from 6 to 24 months for skin dermatitis, subcutaneous tissue fibrosis, bone fractures, joint stiffness and lymphoedema. Toxicities were reported by trial, radiotherapy technique (3D-conformal radiotherapy (3DCRT) and IMRT) and radiotherapy regimen (adjuvant and neo adjuvant) and compared using the Chi2 test. Results Toxicity data from 354 patients were available (193 VorteX; 161 IMRiS). Maximum toxicities from 6 to 24 months are shown in table 1. Adjuvant RT was given to 248 (70%) patients and 3DCRT was given to 180 (50.8%) patients. Skin dermatitis, subcutaneous tissue fibrosis, and bone fractures grade 2 or above (grade2+) toxicities were higher in VorteX trial, except for joint stiffness which was higher in IMRiS. Table 2 shows the comparison of toxicities. Grade2+ toxicities were significantly higher in VorteX (p-value<0.01), 3DCRT and adjuvant & 3DCRT (p-value<0.01). Grade 2+ toxicities in the adjuvant and neo adjuvant RT groups were not significantly different (p=0.07).

Conclusion Grade 2+ toxicity incidence was higher in VORTEX than IMRiS patients, most likely due to patients being treated with adjuvant 3DCRT and to higher radiotherapy doses of 66Gy. Toxicities were significantly higher for 3DCRT than IMRT, the use of 3DCRT cannot be disregarded as this comparison was not done as part of a clinical trial. Both clinical trials provide valuable clinical and dosimetric data from which to develop dose-volume constraints for normal tissue toxicities and to predict for frequency and degree of toxicities for STSE. This work is currently being undertaken. MO-0948 Intermediate-High dose TBI: a balance between disease control and pulmonary toxicity G. Sancho-Pardo 1 , A. Vila 2 , I. Garcia-Cadenas 3 , R. Martino 4 , N. Garcia-Apellaniz 5 , J. Rojas 6 , S. Redondo 4 , S. Bermejo 1 , N. Ventosa 1 , E. Albert 4 , O. Eugenia 1 , S.J. Rabi Mitre 1 , N. Jornet 5 1 Hospital de la Santa Creu i Sant Pau, Radiation Oncology, Barcelona, Spain; 2 Hospital de la Santa Creu i Sant Pau , Radiation Oncology, Barcelona, Spain; 3 Hospital de la Santa Creu i Sant Pau , Hematology, Barcelona, Spain; 4 Hospital de la Santa Creu i Sant Pau, Hematology, Barcelona, Spain; 5 Hospital de la Santa Creu i Sant Pau, Medical Physics, Barcelona, Spain; 6 Hospital de la Santa Creu i Sant Pau, Radiation Oncology, Barcelona , Spain Purpose or Objective Myeloablative conditioning regimens using total body irradiation (TBI) have been associated with reductions in acute leukemia recurrence after allogeneic hematopoietic cell transplant (AHCT) but are accompanied by relevant pulmonary toxicity. In this study we investigate the effect of lung dose reduction and intensified pulmonary protection while keeping a 13.5 Gy prescribed dose on toxicity and survival. Materials and Methods All consecutive adult AHCT recipients who received a TBI-based conditioning due to acute leukemia between 1993 and 2021 were included. All patients were treated with 15 MV photons from LINAC in a semi-standing position, using individualized lung shields hanging in a methacrylate spoiler close to the patient in the beam’s path. From 2010 onwards, margins between the edge of the lung shadow and the edge of the bloc were reduced from 2 cm to 1cm laterally and from 2,5 cm to 1,5 cm craniocaudally. Moreover, lung dose was reduced from 9.5+/- 0,5 Gy to 8.5+/-0,5 Gy. Our aims were to analyse the incidence and risk factors of idiopathic pneumonia syndrome (IPS) and survival. Overall survival (from day 0 to death or last control) and disease-specific survival (considering events in which patients died due to the leukemia or any complication The first author is clinical doctoral research fellow CDR-2018-04-ST2-004, funded by HEE/ NIHR.