Evaluating dosimetric constraints for carbon ion radiotherapy in the treatment of locally advanced pancreatic cancer

Nitin Ohri,Xiaodong Wu,Zheng Wang,Chandan Guha,Lien-Chun Lin,Guo-Liang Jiang,Jiade J. Lu,Madhur Garg

doi:10.1186/s13014-020-01515-5

Abstract

ObjectiveTo identify a safe carbon ion radiotherapy (CIRT) regimen for patients with locally advanced pancreatic cancer (LAPC).MethodsWe generated treatment plans for 13 consecutive, unselected patients who were treated for LAPC with CIRT at our center using three dose and fractionation schedules: 4.6 GyRBE × 12, 4.0 GyRBE × 14, and 3.0 GyRBE × 17. We tested the ability to meet published dose constraints for the duodenum, stomach, and small bowel as a function of dose schedule and distance between the tumor and organs at risk.ResultsUsing 4.6 GyRBE × 12 and 4.0 GyRBE × 14, critical (high-dose) constraints could only reliably be achieved when target volumes were not immediately adjacent to organs at risk. Critical constraints could be met in all cases using 3.0 GyRBE × 17. Low-dose constraints could not uniformly be achieved using any dose schedule.ConclusionWhile selected patients with LAPC may be treated safely with a CIRT regimen of 4.6 GyRBE × 12, our dosimetric analyses indicate that a more conservative schedule of 3.0 GyRBE × 17 may be required to safely treat a broader population of LAPC patients, including those with large tumors and tumors that approach gastrointestinal organs at risk. The result of this work was used to guide an ongoing clinical trial.

Highlights

Pancreatic cancer is a leading cause of cancer mortality, accounting for over 300,000 deaths each year [1]
Randomized trials seeking to demonstrate the superiority of chemoradiotherapy over chemotherapy alone have yielded mixed results [3,4,5,6, 8, 9]
Carbon ion radiotherapy planning and treatment Patients are treated in the prone position. 4-dimensional simulation CT imaging with ten phases is obtained in the treatment position, and a gating window in the expiration phase during which target motion is no more than 5 mm is selected

Summary

Introduction

Pancreatic cancer is a leading cause of cancer mortality, accounting for over 300,000 deaths each year [1]. 30% of pancreatic cancer patients present with locally advanced disease, which may be defined as unresectable disease without evidence of distant metastases. Randomized trials seeking to demonstrate the superiority of chemoradiotherapy over chemotherapy alone have yielded mixed results [3,4,5,6, 8, 9]. All of these studies utilized photon radiotherapy. In the one trial that employed an unusually high radiotherapy dose of 60 Gy, chemoradiotherapy yielded significantly shorter overall survival duration

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Results

Conclusion