Dosimetric analysis of brachial plexopathy after stereotactic body radiotherapy: Significance of organ delineation

• Published in: Radiotherapy and oncology 2024-01, Vol.190, p.110023, Article 110023
• Main Authors: Niu, Geng-Min, Gao, Miao-Miao, Wang, Xiao-Feng, Dong, Yang, Zhang, Yi-Fan, Wang, Huan-Huan, Guan, Yong, Cheng, Ze-Yuan, Zhao, Shu-Zhou, Song, Yong-Chun, Tao, Zhen, Zhao, Lu-Jun, Meng, Mao-Bin, Spring Kong, Feng-Ming, Yuan, Zhi-Yong
• Format: Article
• Language: English
• Subjects: Brachial plexopathy; Brachial Plexus Neuropathies - etiology; Delineation; Dosimetric analysis; Humans; Organs at Risk; Radiation Injuries; Radiosurgery - adverse effects; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted; Stereotactic body radiotherapy
• ISSN: 0167-8140; 1879-0887; 1879-0887
• DOI: 10.1016/j.radonc.2023.110023

•Contouring subclavian-axillary veins underestimates grade ≥ 2 RIBP risk in dosimetry.•Significant underestimation of BP doses was observed in patients with PTV-B.•Maximum and 0.3 cc biologically effective doses to BP may be predictors of RIBP. Examine the significance of contouring the brachial plexus (BP) for toxicity estimation and select metrics for predicting radiation-induced brachial plexopathy (RIBP) after stereotactic body radiotherapy. Patients with planning target volume (PTV) ≤ 2 cm from the BP were eligible. The BP was contoured primarily according to the RTOG 1106 atlas, while subclavian-axillary veins (SAV) were contoured according to RTOG 0236. Apical PTVs were classified as anterior (PTV-A) or posterior (PTV-B) PTVs. Variables predicting grade 2 or higher RIBP (RIBP2) were selected through least absolute shrinkage and selection operator regression and logistic regression. Among 137 patients with 140 BPs (median follow-up, 32.1 months), 11 experienced RIBP2. For patients with RIBP2, the maximum physical dose to the BP (BP-Dmax) was 46.5 Gy (median; range, 35.7 to 60.7 Gy). Of these patients, 54.5 % (6/11) satisfied the RTOG limits when using SAV delineation; among them, 83.3 % (5/6) had PTV-B. For patients with PTV-B, the maximum physical dose to SAV (SAV-Dmax) was 11.2 Gy (median) lower than BP-Dmax. Maximum and 0.3 cc biologically effective doses to the BP based on the linear-quadratic-linear model (BP-BEDmax LQL and BP-BED0.3cc LQL, α/β = 3) were selected as predictive variables with thresholds of 118 and 73 Gy, respectively. Contouring SAV may significantly underestimate the RIBP2 risk in dosimetry, especially for patients with PTV-B. BP contouring indicated BP-BED0.3cc LQL and BP-BEDmax LQL as potential predictors of RIBP2.