Dosimetric parameters correlate with duodenal histopathologic damage after stereotactic body radiotherapy for pancreatic cancer: Secondary analysis of a prospective clinical trial

Abstract

Purpose: Prospectively assess relationships between dosimetric parameters and histopathologic/clinical duodenal toxicities in patients on a phase I trial for pancreatic cancer.

Methods: Forty-six borderline resectable/unresectable patients were enrolled on a prospective trial testing neoadjuvant gemcitabine/5-fluorouracil followed by SBRT (5 daily fractions of 5-8Gy) and concurrent nelfinavir. Post-SBRT surgery was performed in 13 resectable patients, which constituted the patient population herein. Pathologic duodenal damage was assessed using predetermined criteria: 1, no/minimal; 2, moderate; and 3, marked damage. Clinical toxicities were assessed per the Clinical Terminology Criteria for Adverse Events (CTCAE). Duodenal dosimetric parameters included V5-V40 and mean/maximum doses. Spearman correlation and linear regression evaluated associations between dosimetric parameters and clinical/pathologic duodenal toxicity.

Results: The median duodenal mean and maximum doses were 20 and 37Gy. Median duodenal V5-V40 were 64, 62, 52, 39, 27, 14, 5 and 0cc, respectively. The median duodenal damage score was 2 (four 1, eight 2, and one 3). Higher duodenal damage scores correlated with higher duodenal mean doses (r=0.75, p=0.003), V35 (r=0.61, p=0.03), V30 (r=0.67, p=0.01), V25 (r=0.68, p=0.01), V20 (r=0.56, p=0.05), and the planning target volume (PTV) mean (r=0.59, p=0.03) and maximum (r=0.61, p=0.03) doses. Clinical toxicities did not correlate with dosimetric parameters or duodenal pathologic damage.

Conclusions: Duodenal histologic damage correlates with mean duodenal dose, V20-V35, and PTV mean/maximum doses.

Keywords: Duodenum; Pancreatic cancer; Stereotactic body radiotherapy; Toxicity.

Conflict of interest statement

Conflicts of interest

The authors all declare that conflicts of interest do not exist. There were no funding sources for this study.

Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.

Figures

Fig. 1

Histologic examples of grade 1 (Panel A), grade 2 (Panel B), and grade 3 (Panel C) duodenal damage.

Fig. 2

Fit plots with best-fit lines of duodenal histopathologic damage score (y-axis) as a function of mean duodenal dose (Gy) (Panel A), duodenal V25 (cc) (Panel B), duodenal V30 (cc) (Panel C), and duodenal V35 (cc) (Panel D).