Application of Real-Time Tumor-Tracking and Gated Radiotherapy System for Unresectable Pancreatic Cancer

ABSTRACT

Herein is reported our experience of radiation therapy using a real-time tumor-tracking and gated radiotherapy (RTRT) system for inoperable pancreatic cancer. Three unresectable pancreatic cancer patients were treated with intraoperative electron beam radiation therapy, at the time of open biopsy, and postoperative external beam radiation therapy using an RTRT system with a 2.0 mm diameter gold ball implanted into the pancreas. The total BED's (alpha/beta=10) was intended to be equivalent to that of delivering 60 Gy by 2.0 Gy/fraction, while the actual dose schedules were individualized. The movement of the pancreas was analyzed based on the 3-dimensional marker positions during the RTRT. The side effects and tumor responses were evaluated. During the RTRT course, the average movement of markers in the x (left to right), y (cranial to caudal) and z (dorsal to ventral) directions were 3.0 mm (1.7- 5.2 mm), 5.2 mm (3.5 - 6.8 mm) and 3.5 mm (2.7 - 5.1 mm), respectively. During and after the course of postoperative radiation therapy, no acute side effects of RTOG grade II or higher were detected. The objective tumor responses, as evaluated by CT scans 3 months after the treatment, were 2 partial responses and no response in one patient. Using the RTRT technique the margin of treatment planning and the possible errors in target localization were reduced, and the 3-dimensional movement of the internal marker implanted in the pancreas was able to be analyzed.