Five-Fraction Radiotherapy for Breast Cancer: Which are the Most Suitable Patients?

ABSTRACT

FAST-Forward trial reported that five-fraction radiotherapy (5fx-RT) schedule with 26 Gy in adjuvant setting after breast-conserving surgery for early-breast cancer (BC) was non-inferior to the standard hypo-fx (SHfx) schedule with 40 Gy in 15fx in terms of local tumor control. Since the COVID-19 pandemic started RT expert groups encouraged professionals to implement hypo-fx schedules in order to decrease visits of patients to hospitals. The aim of this study is to help radiation oncologists choose the most suitable patients for 5fx-RT schedule according to anatomical features. Between March 2020 and December 2021, 239 patients suitable for 5fx-RT schedule were referred to our department. Prescribed RT dose was 26 Gy in 5fx to the whole breast plus a simultaneously integrated boost (SIB) up to 29 Gy to tumor bed if indicated. Patients were divided into 3 groups Group A Patients treated with 5fx-RT schedule that met all the FAST-Forward constraints for normal tissues;Group B Patients treated with 5fx-RT schedule that slightly did not meet all constraints, Group C Patients switched to SHfx schedule as they did not meet constraints in an acceptable way. For each patient, we draw an imaginary straight line connecting the medial and lateral borders of PTV in the axial slice of simulation CT where the longest anteroposterior diameter was found. From midpoint of this line, we measured the tangent distance to PTV margin and collected the data as medial-to-lateral tangent (MELT). Data was analyzed using statistical software. 150 patients were included in group A, 75 in group B and 14 in group C. The median MELT distance was 1.91cm, 2.48cm and 3cm respectively. We found that the increase in MELT distance was significantly associated with a poorer compliance of normal tissue constraints (p<0.0001). Patient´s distribution among 3 groups for MELT distance intervals are shown in table 1. Median V8 for ipsilateral lung was 13.1, 15.46 and 20.49% for groups A, B and C respectively. For the heart, median mean dose was 1.06, 1.8 and 2.25 Gy for left breast cancer patients and 0.28, 0.33 and 0.48 Gy for right breast cancer patients for groups A, B and C respectively. We found a moderate positive correlation between MELT distance and dosimetric parameters assessed above (r=0.545, 0.475 and 0.418 respectively). According to laterality, for a higher MELT distance the % of left BC patients increased significantly (p=0.039). MELT distance is an easy tool that helps radiation oncologists predict which BC patients are the most suitable for 5fx-RT before RT planning begins. This could avoid delays in starting RT for patients with a high MELT distance directly planning them with the SHfx schedule. [ FROM AUTHOR] Copyright of International Journal of Radiation Oncology, Biology, Physics is the property of Pergamon Press - An Imprint of Elsevier Science and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full . (Copyright applies to all s.)