Predictors of Radiotherapy-related GI Toxicity from Anal Cancer DP-IMRT: Secondary Analysis of NRG Oncology RTOG 0529

Publication date: Available online 13 February 2017
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Jeffrey Olsen, Jennifer Moughan, Robert Myerson, Andre Abitbol, Desiree E. Doncals, Douglas Johnson, Tracey E. Schefter, Yuhchyau Chen, Barbara Fisher, Jeff Michalski, Samir Narayan, Albert Chang, Christopher H. Crane, Lisa Kachnic
PurposeStudy XXXX assessed the feasibility of dose-painted intensity-modulated radiation therapy (DP-IMRT) to reduce the acute morbidity of chemoradiation with 5-fluorouracil (5FU) and mitomycin-C (MMC) for T2-4N0-3M0 anal cancer. This secondary analysis was performed to identify patient and treatment factors associated with acute and late gastrointestinal (GI) adverse events (AEs).Methods and MaterialsStudy XXXX treatment plans were reviewed to extract dose-volume data for tightly contoured small bowel, loosely contoured anterior pelvic contents (APC), and uninvolved colon outside the target volume (UC). Univariate logistic regression was performed to evaluate association between volumes of each structure receiving doses ≥ 5 to 60 Gy (V5-V60) in 5 Gy increments between patients with and without ≥ grade (G) 2, acute and late GI AEs, and ≥G3 acute GI AEs. Additional patient and treatment factors were evaluated in multivariate (MV) logistic regression (acute AEs) or Cox proportional hazards models (late AEs).ResultsAmong 52 evaluable patients, ≥G2 acute, ≥G2 late, and ≥G3 acute GI AEs were observed in 35, 17, and 10 patients, respectively. Trends (p<0.05) towards statistically significant associations were observed between: ≥G2 acute GI AEs and small bowel dose (V20-V40); ≥G2 late GI AEs and APC dose (V60); ≥G3 acute GI AEs and APC dose (V5-V25), increasing age, tumor size >4cm, and worse Zubrod. Small bowel volumes of 186.0 cc, 155.0 cc, 41.0 cc, and 30.4 cc receiving doses greater than 25, 30, 35, and 40 Gy, respectively, correlated with increased risk of acute ≥ grade 2 GI AEs.ConclusionsAcute and late GI AEs from 5FU/MMC chemoradiation using DP-IMRT correlate with radiation dose to the small bowel and APC. Such associations will be incorporated in the dose-volume normal tissue constraint design for future XXXX anal cancer studies.

Teaser

In this secondary analysis of Study XXXX, acute and late gastrointestinal adverse events from 5FU/MMC chemoradiation using DP-IMRT for anal cancer treatment were found to correlate with radiation dose to the small bowel and anterior pelvic contents. Specific small bowel threshold-doses are of interest for IMRT optimization in future studies to reduce the risk of gastrointestinal adverse events.


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