Effect And Safety Of Proton Beam Therapy For Locally Recurrent Rectal Cancer.

743Background: The first choice of treatment for locally recurrent rectal cancer is surgical resection. However, the operation is often difficult with high perioperative risk. For surgically unfit cases, proton beam therapy (PBT) is proposed as the treatment option. However, its efficacy for locally recurrent rectal cancer remains unclear. Therefore, this study aimed to evaluate the efficacy and safety of PBT for locally recurrent rectal cancer. Methods: A total of 23 patients with locally recurrent rectal cancer who received PBT were retrospectively evaluated, from November 2005 to July 2014. Patients with single lesion, who refuse the radical surgical therapy, or who were considered unfit for the operation were included in this study. All patients were treated with 2.8Gy relative biological effectiveness (RBE)/fraction. Twenty-five irradiations were performed, with a total irradiation of 70Gy RBE. Unfit for operation criteria include invasion to the vertebra higher than the third sacrum or lateral lymph...