Predictor of severe gastroduodenal toxicity after stereotactic body radiotherapy for abdominopelvic malignancies.

PURPOSE: To identify the predictors for the development of severe gastroduodenal toxicity (GDT) in patients treated with stereotactic body radiotherapy (SBRT) using 3 fractionations for abdominopelvic malignancies. METHODS AND MATERIALS: From 2001 to 2011, 202 patients with abdominopelvic malignancies were treated with curative-intent SBRT. Among these patients, we retrospectively reviewed the clinical records of 40 patients with the eligibility criteria as follows: 3 fractionations, follow-up period≥1 year, absence of previous radiation therapy (RT) history or combination of external-beam RT and the presence of gastroduodenum (GD) that received a dose higher than 20% of prescribed dose. The median SBRT dose was 45 Gy (range, 33-60 Gy) with 3 fractions. We analyzed the clinical and dosimetric parameters, including multiple dose-volume histogram endpoints: V20 (volume of GD that received 20 Gy), V25, V30, V35, and Dmax (the maximum point dose). The grade of GDT was defined by the National Cancer Institute Common Toxicity Criteria version 4.0, and GDT≥grade 3 was defined as severe GDT.
RESULTS: The median time to the development of severe GDT was 6 months (range, 3-12 months). Severe GDT was found in 6 patients (15%). Dmax was the best dosimetric predictor for severe GDT. Dmax of 35 Gy and 38 Gy were respectively associated with a 5% and 10% probability of the development of severe GDT. A history of ulcer before SBRT was the best clinical predictor on univariate analysis (P=.0001).
CONCLUSIONS: We suggest that Dmax is a valuable predictor of severe GDT after SBRT using 3 fractionations for abdominopelvic malignancies. A history of ulcer before SBRT should be carefully considered as a clinical predictor, especially in patients who receive a high dose to GD.