AUTHOR=Cao Yangsen , Zhu Xiaofei , Yu Chunshan , Jiang Lingong , Sun Yongjian , Guo Xueling , Zhang Huojun 

TITLE=Dose evaluations of organs at risk and predictions of gastrointestinal toxicity after re-irradiation with stereotactic body radiation therapy for pancreatic cancer by deformable image registration

JOURNAL=Frontiers in Oncology

VOLUME=Volume 12 - 2022

YEAR=2023

URL=https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2022.1021058

DOI=10.3389/fonc.2022.1021058

ISSN=2234-943X

ABSTRACT=Purpose: Re-irradiation of local recurrence of pancreatic cancer may be an optimal choice as the local ablative therapy. However, dose constraints of organs at risk (OARs) predictive of severe toxicity remains unknown. Therefore, we aim to calculate and identify accumulated dose distributions of OARs correlating with severe adverse effects, and determine possible dose constraints regarding re-irradiation.
Methods: Patients receiving two courses of SBRT for the same irradiated regions (the primary tumors) due to local recurrence were included. All doses of the first and second plans were recalculated to an Equivalent Dose of 2 Gy per fraction (EQD2). Deformable image registration with the workflow “Dose Accumulation-Deformable” of MIM® System (version: 6.6.8) was performed for dose summations. Dose-volume parameters predictive of grade 2 or more toxicities were identified and receiver operator characteristic (ROC) was used to determine optimal thresholds of dose constraints.
Results: Forty patients were included in the analysis. Only V10 of the stomach (HR: 1.02 [95% CI:1.00-1.04], P=0.035) and Dmean of the intestine (HR: 1.78 [95%CI: 1.00-3.18], P=0.049) correlated with grade 2 or more gastrointestinal toxicity. Hence, the equation of probability of such toxicity was P=1/(1+e^(-(-4.155+0.579Dmean of the intestine+0.021V10 of the stomach)) ). Additionally, the area under the ROC curve and threshold of dose constraints of V10 of the stomach and Dmean of the intestine was 0.779 and 77.575cc, 0.769 and 4.22Gy3 (α/β=3). The area under the ROC curve of the equation was 0.821.
Conclusion: V10 of the stomach and Dmean of the intestine may be vital parameters to predict grade 2 or more gastrointestinal toxicity, of which the threshold of dose constraints may be beneficial for practice of re-irradiation of local relapsed pancreatic cancer.