Purpose: Pencil-beam scanning intensity modulated proton therapy (IMPT) may allow for an improvement in the therapeutic ratio compared with conventional techniques of radiation therapy delivery for pancreatic cancer. The purpose of this study was to describe the clinical implementation of IMPT for intact and clinically localized pancreatic cancer, perform a matched dosimetric comparison with volumetric modulated arc therapy (VMAT), and report acute adverse event (AE) rates and patient-reported outcomes (PROs) of health-related quality of life.
Methods and materials: Between July 2016 and March 2017, 13 patients with localized pancreatic cancer underwent concurrent capecitabine or 5-fluorouracil-based chemoradiation therapy (CRT) utilizing IMPT to a dose of 50 Gy (radiobiological effectiveness: 1.1). A VMAT plan was generated for each patient to use for dosimetric comparison. Patients were assessed prospectively for AEs and completed PRO questionnaires utilizing the Functional Assessment of Cancer Therapy-Hepatobiliary at baseline and upon completion of CRT.
Results: There was no difference in mean target coverage between IMPT and VMAT (P > .05). IMPT offered significant reductions in dose to organs at risk, including the small bowel, duodenum, stomach, large bowel, liver, and kidneys (P < .05). All patients completed treatment without radiation therapy breaks. The median weight loss during treatment was 1.6 kg (range, 0.1-5.7 kg). No patients experienced grade ≥3 treatment-related AEs. The median Functional Assessment of Cancer Therapy-Hepatobiliary scores prior to versus at the end of CRT were 142 (range, 113-163) versus 136 (range, 107-173; P = .18).
Conclusions: Pencil-beam scanning IMPT was feasible and offered significant reductions in radiation exposure to multiple gastrointestinal organs at risk. IMPT was associated with no grade ≥3 gastrointestinal AEs and no change in baseline PROs, but the conclusions are limited due to the patient sample size. Further clinical studies are warranted to evaluate whether these dosimetric advantages translate into clinically meaningful benefits.