Proton and carbon ion radiation therapy for locally advanced pancreatic cancer: A phase I dose escalation study

To determine the maximum tolerated dose (MTD) of proton and carbon ion radiation therapy (PCRT) for locally advanced pancreatic cancer (LAPC).

A single-institution, phase I dose escalation study was performed. The proton dose of 50.4 GyE in 28 fractions was delivered to clinical target volume, and carbon ion as a boost dose to gross tumor volume escalated from 12 GyE to 18 GyE with 3 GyE per fraction in 3 dose levels. The dose limiting toxicity (DLT) was defined as any treatment-related grade (G)3 or higher of non-hematological toxicity. The MTD was exceeded if ≥2 patients in a dose level developed DLT.

From May 2015 to July 2016, ten patients were enrolled, 3 in dose level 1, 4 in dose level 2, and 3 in dose level 3. With a median follow-up of 17.4 months, no patient developed a DLT, and the acute G1-2 of gastrointestinal (GI) and hepatic toxicity occurred in 40% of patients, and G1 of GI late toxicity, in 30%. The median overall survival was 17.3 months.

Higher than 50.4 GyE could be given by PCRT with slight toxicity and good tolerance for LAPC, and the tumor control and survival had been improved, but not significantly. Better outcome may be achieved using carbon ion radiation therapy with higher biological equivalent dose.