Safety & feasibility of SIB in extreme 1-week hypofractionated radiotherapy for early breast cancer
Luis Mateu Castell,
Spain
PO-1297
Abstract
Safety & feasibility of SIB in extreme 1-week hypofractionated radiotherapy for early breast cancer
Authors: Carlos Garcia Zanoguera1,2, Jon Gadea Quinteiro1,2, Alba Galatea Curbelo Artiles1, Luis Mateu Castell1, Irene Ortiz Gonzalez1, Jose Pardo Masferrer1,2
1Hospital Universitario Son Espases, Servicio de Oncología Radioterápica, Islas Baleares, Spain; 2IdiSBa, Institut d’Investigació Sanitaria de les Illes Balears, Islas Baleares, Spain
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Purpose or Objective
The phase 3 FAST-Forward trial reported that 26Gy in 5 fractions (fx) over 1 week for early-breast cancer patients after breast conserving surgery was non-inferior to the standard 40Gy in 15fx over 3 weeks for local tumor control and normal tissue effects. In this study, a sequential tumor bed boost was allowed (10 or 16Gy in 2Gy/fx) if required. The aim of our study is to evaluate the safety and feasibility of a simultaneous integrated boost (SIB) up to 29/30Gy over 5fx in order to avoid treatment lengthening when a boost is indicated.
Material and Methods
From March 2020 to December 2021, 126 patients eligible for 5fx-RT schedule were referred to our institution and selected for the analysis. A SIB to the tumor bed up to 29Gy in 5fx of 5.8Gy was indicated when any of the following criteria appeared: Age < 60 years, high-grade tumors and lymphovascular or perineural invasion. When positive margins were observed in the histological exam, a SIB up to 30Gy in 5fx of 6Gy was prescribed. Patient´s toxicity was assessed at 4 different points: During RT and at 1, 6 and 12 months follow-up. Toxicity was evaluated using CTCAE 5.0 criteria.
Results
Mean follow-up was 6.25 months and mean age was 56 years (32-83). During RT course, no toxicities were observed. G1-2 dermatitis was observed in 9 patients at first month assessment, but all of them had disappeared at 6 months after RT. According to skin-color changes, 11% of the patients presented skin hyperpigmentation at first month assessment but in most cases was not observed in subsequent evaluations. Only 4% of the patients presented G1 fatigue and skin induration in the first medical visit after RT. No severe toxicities were found in any patient at any time during follow-up. Complete details are shown in table 1. In addition, one patient developed mastitis during the first month after RT but was easily solved with oral antibiotics.
![](https://www.estro.org:443/ESTRO/media/Abstracts/295/25139da5-f7c8-40ac-8766-573d6d4a3049.jpeg)
Conclusion
According to our data, administration of SIB up to 29/30Gy in 5fx is safe and feasible for early-breast cancer patients requiring adjuvant RT after breast conserving surgery. SIB could replace sequential boost in these patients shortening the RT treatment and improving patients’ compliance and comfort. Further follow-up is needed in order to assess chronic toxicity.