ESTRO 2022 - Abstract Book

S997

Abstract book

ESTRO 2022

advantage of automatic monitoring based on the quantification of intra fraction movement. To conclude, AlignRT is an efficient system for the initial set up of VMAT breast or chest wall involving lymph nodes radiotherapy.

PO-1176 Dermal recall effect in breast radiotherapy patients after vaccine administration

V. García Reglero 1 , S. Vazquez Gonzalez 2 , E. García Alonso 3 , J.E. Baquedano Baquedano 3 , R. Robaina 3 , M. Bonet Beltran 3 , D. González gómez 3 , L. Tueros Farfan 4 , N. El Jarroudi 5 , M. Mira Flores 3 1 H.U Arnau de Vilanova, Radiation Oncology , Lleida, Spain; 2 H.U Arnau de Vilanova , Radiation Oncology, Lleida, Spain; 3 H.U Arnau de Vilanova, Radiation Oncology, Lleida, Spain; 4 H.U Arnau de Vilanova, radiation Oncology, Lleida, Spain; 5 H.U Arnau de Vilanova, radiation Oncology, lleida, Spain Purpose or Objective The dermal recall phenomenon is an increase in the sensitivity of stem cells in the area of the treatment field and may lead to increased acute toxicity. Afterwards, the recall effect has been described in those patients who have been vaccinated against COVID during radiotherapy treatment. Our objective has been to observe if we are facing a dermal recall phenomenon after the administration of the vaccine in patients who are on the course of radiotherapy. Materials and Methods Coinciding with the vaccination campaign against SARS-CoV-2 in oncological patients, which began in our environment in March 2021, we have collected data on radiodermatitis that have been presented by 42 patients after the end of radiation therapy treatment for breast cancer Results The percentage of patients vaccinated were as follows: 57% (24/ 42 patients) Of which 6/24 patients received the vaccine dose during radiation therapy Of the 42 patients treated with radiation therapy, 3 had a degree 3 dermal toxicity. These 3 patients were given the vaccine during radiotherapy treatment, which accounts for 50% of the patients vaccinated during radiotherapy. Note that of the 845 patients treated with hypofractionation radiotherapy since 2016 only 0.23% have presented grade 3 acute radiodermatitis, versus 7% of the patients who have been vaccinated during radiotherapy Conclusion We estimate that most likely, the vaccine carries a greater risk of skin toxicity mediated by the dermal recall phenomenon but that does not mean that the administration of the vaccine should be contraindicated, but more closely warn patients who receive the vaccine during radiation therapy. R. Tummineri 1 , A. Fodor 1 , F. Zerbetto 1 , M. Pasetti 1 , C.L. Deantoni 1 , A. Sanchez Galvan 2 , R. Castriconi 3 , P. Mangili 3 , A. Del Vecchio 3 , N.G. Di Muzio 4 1 IRCCS San Raffaele Scientific Institute, Radiation Oncology, Milano, Italy; 2 Milano-Bicocca University, Radiation Oncology, Milano, Italy; 3 IRCCS San Raffaele Scientific Institute, Medical Physics, Milano, Italy; 4 IRCCS San Raffaele Scientific Institute - Università Vita-Salute, Radiation Oncology, Milano, Italy Purpose or Objective Hypofractionated whole breast radiotherapy is considered the standard after conservative surgery for breast cancer (BCa), but the interest in hypofractionation is growing even for locoregional treatments, involving not only breast/chest wall, but also lymph nodal (LN) areas. We report acute toxicity in patients with advanced BCa treated with hypofractionated radiotherapy (HRT) to breast/chest wall and regional LN in our Institute. Materials and Methods From 03/2018 to 05/2021 132 pts with diagnosis of advanced BCa pts (98% female, 2% male) underwent locoregional HRT after conservative surgery (58%) or mastectomy (40.5%), and 3 pts received radical RT (1.5%). Two pts had bilateral BCa (134 irradiated breasts). Median age was 52 (26-86) years. Molecular subtypes were: Luminal A 29%, Luminal B Her2- 28.5%, Luminal B Her+ 19%, HR negative Her2+ 13% and Triple negative 10.5%. Neoadjuvant chemotherapy was prescribed in 55% of pts, adjuvant in 55%, and concomitant in 11%. Adjuvant hormonal therapy was prescribed in 76% of pts (IA or TMX -/+ LH-RH analogue). Thirty-three % of pts underwent HER2-targeted therapy. Treatments were delivered with 3DCRT (11%), VMAT (30%) or Tomotherapy (59%, TomoDirect or TomoHelical), to a total dose of 40.05 Gy in 15 fractions, delivered in 3 weeks, to breast/chest wall and regional LNs. A simultaneous integrated boost (SIB) up to 48 Gy to the tumor bed was delivered for pts with high-risk local relapse. The target was: whole breast in 60% (46% right, 54% left), chest wall in 40% (40% right, 60% left, 33% without and 67% with post-mastectomy reconstruction), supraclavicular LN in 100%, axillary LN in 34.4%, and internal mammary chain in 13.5% of cases, respectively. A SIB to the tumor bed was delivered in 34.5% of pts. Acute toxicity was registered according to CTCAE v 4.0. PO-1177 Acute toxicity of hypofractionated locoregional radiotherapy in advanced breast cancer

Results