A dosimetric model of duodenal toxicity after stereotactic body radiotherapy for pancreatic cancer

James D. Murphy, Claudia Christman-Skieller, Jeff Kim, Sonja Dieterich, Daniel T. Chang, Albert C. Koong

Research output: Contribution to journalArticlepeer-review

94 Scopus citations

Abstract

Introduction: Dose escalation for pancreas cancer is limited by the tolerance of adjacent normal tissues, especially with stereotactic body radiotherapy (SBRT). The duodenum is generally considered to be the organ at greatest risk. This study reports on the dosimetric determinants of duodenal toxicity with single-fraction SBRT. Methods and Materials: Seventy-three patients with locally advanced unresectable pancreatic adenocarcinoma received 25 Gy in a single fraction. Dose-volume histogram (DVH) endpoints evaluated include V5 (volume of duodenum that received 5 Gy), V10, V15, V20, V25, and Dmax (maximum dose to 1 cm3). Normal tissue complication probability (NTCP) was evaluated with a Lyman model. Univariate and multivariate analyses were conducted with Kaplan-Meier and Cox regression models. Results: The median time to Grade 2-4 duodenal toxicity was 6.3 months (range, 1.6-11.8 months). The 6- and 12-month actuarial rates of toxicity were 11% and 29%, respectively. V 10-V25 and Dmax all correlated significantly with duodenal toxicity (p < 0.05). In particular, V15 ≥ 9.1 cm3 and V15 < 9.1 cm3 yielded duodenal toxicity rates of 52% and 11%, respectively (p = 0.002); V20 ≥ 3.3 cm3 and V20 < 3.3 cm3 gave toxicity rates of 52% and 11%, respectively (p = 0.002); and Dmax ≥ 23 Gy and Dmax < 23 Gy gave toxicity rates of 49% and 12%, respectively (p = 0.004). Lyman NTCP model optimization generated the coefficients m = 0.23, n = 0.12, and TD50 = 24.6 Gy. Only the Lyman NTCP model remained significant in multivariate analysis (p = 0.001). Conclusions: Multiple DVH endpoints and a Lyman NTCP model are strongly predictive of duodenal toxicity after SBRT for pancreatic cancer. These dose constraints will be valuable in future abdominal SBRT studies.

Original languageEnglish (US)
Pages (from-to)1420-1426
Number of pages7
JournalInternational Journal of Radiation Oncology Biology Physics
Volume78
Issue number5
DOIs
StatePublished - Dec 1 2010
Externally publishedYes

Keywords

  • Lyman model
  • NTCP
  • Pancreas cancer
  • SBRT
  • Toxicity

ASJC Scopus subject areas

  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Radiation
  • Cancer Research

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