A phase I dose escalation study of carbon-ion radiotherapy for pancreatic cancer.

TPS768 Background: Despite recent advances in chemotherapy and radiotherapy, the prognosis of unresectable locally pancreatic cancer (LAPC) patients remains poor. To improve the outcome, we have developed carbon ion radiotherapy (C-ion RT) for pancreatic cancer and have shown good results against conventional photon therapy. Compared to conventional photon therapy, C-ion RT can safely administer higher doses, and we find the possibility of long-term survival for some unresectable LAPC. Currently, C-ion RT is performed using 55.2 Gy (RBE) in 12 fractions. However local control is not satisfactory. Further dose escalation needs to be safely administered to further improve outcomes. We have developed a new treatment strategy: intensity-modulated ion therapy using the simultaneous integrated boost method and the linear transfer energy (LET) optimization method. We believe that these cutting-edge technologies will allow for a more intensive effect on pancreatic cancer. Thus, we started a clinical trial to evaluate the safety of dose escalation using these novel techniques. Methods: Eligibility included pathological or clinical confirmation of pancreatic cancer without distant metastasis. Carbon ion radiotherapy is given in 12 fractions over 3 weeks. The radiation doses are set in four steps, with increases ranging from 55.2 Gy (RBE) to 67.2 Gy (RBE). A minimum of three patients is enrolled in each cohort, and if there is no dose limiting toxicity (DLT), a dose escalation is performed. The primary endpoint is acute adverse events; the secondary outcomes are late adverse events, local control rate, and overall survival. We started this trial in September 2021. Cohort 1 has been completed without DLT. Cohort 2 is now starting enrollment. Clinical trial information: jRCTs032210292 .