Analysis of dosimetric parameters associated with acute gastrointestinal toxicity and upper gastrointestinal bleeding in locally advanced pancreatic cancer patients treated with gemcitabine-based concurrent chemoradiotherapy.

Purpose: To identify the dosimetric parameters associated with gastrointestinal (GI) toxicity in patients with locally advanced pancreatic cancer (LAPC) treated with gemcitabine-based chemoradiotherapy.
Methods and Materials: The data from 40 patients were analyzed retrospectively. Chemoradiotherapy consisted of conventional fractionated three-dimensional radiotherapy and weekly gemcitabine. Treatment-related acute GI toxicity and upper GI bleeding (UGB) were graded according to the Common Toxicity Criteria Adverse Events, version 4.0. The dosimetric parameters (mean dose, maximal absolute dose which covers 2 cm(3) of the organ, and absolute volume receiving 10-50 Gy [V(10-50)]) of the stomach, duodenum, small intestine, and a composite structure of the stomach and duodenum (StoDuo) were obtained. The planning target volume was also obtained. Univariate analyses were performed to identify the predictive factors for the risk of grade 2 or greater acute GI toxicity and grade 3 or greater UGB, respectively.
Results: The median follow-up period was 15.7 months (range, 4-37). The actual incidence of acute GI toxicity was 33%. The estimated incidence of UGB at 1 year was 20%. Regarding acute GI toxicity, a V(50) of ≥ 16 cm(3) of the stomach was the best predictor, and the actual incidence in patients with V(50) <16 cm(3) of the stomach vs. those with V(50) of ≥ 16 cm(3) was 9% vs. 61%, respectively (p = 0.001). Regarding UGB, V(50) of ≥ 33 cm(3) of the StoDuo was the best predictor, and the estimated incidence at 1 year in patients with V(50) <33 cm(3) of the StoDuo vs. those with V(50) ≥ 33 cm(3) was 0% vs. 44%, respectively (p = 0.002). The dosimetric parameters correlated highly with one another.
Conclusion: The irradiated absolute volume of the stomach and duodenum are important for the risk of acute GI toxicity and UGB. These results could be helpful in escalating the radiation doses using novel techniques, such as intensity-modulated radiotherapy, for the treatment of pancreatic cancer.
(Copyright © 2012 Elsevier Inc. All rights reserved.)