SU‐E‐T‐637: IMRT for Pancreas and Prostate Cancer Using Pulsed Low Dose Rate Delivery Techniques

Abstract

Purpose: Reirradiation of patients previously treated with radiotherapy is vastly challenging. Pulsed low dose rate (PLDR) external beam radiotherapy has the potential to reduce normal tissue toxicities while still providing significant tumor control for recurrent cancers. This work investigates treatment planning techniques for IMRT‐based PLDR treatment for various sites, including pancreatic and prostate cancer cases. Methods: Treatment plans were generated with 10 gantry angles using the step‐and‐shoot delivery technique, which can be delivered in three‐minute intervals to achieve an effective low‐dose rate of 6.67cGy/min. The IMRT plans were compared with the 3DCRT plans and RapidArc plans in this study. Results: For the ten pancreas cases investigated, the mean PTV dose for each gantry angle in the IMRT plans ranged from 17.6 cGy to 22.4 cGy. The maximum doses ranged between 22.9 cGy and 34.8 cGy. The minimum doses ranged from 8.2 cGy to 17.5 cGy. For the ten prostate cases investigated, the mean PTV doses for individual gantry angles ranged from 18.8 cGy to 22.6 cGy. The maximum doses per gantry angle were between 24.0 cGy and 34.7 cGy. The minimum doses per gantry angle ranged from 4.4 cGy to 17.4 cGy. Conclusion: A significant reduction in the OAR dose was achieved with IMRT compared with 3DCRT. For most OARs, no significant differences were observed between IMRT and RapidArc. Compared with 3DCRT, IMRT could provide superior target coverage and normal tissue sparing for PLDR reirradiation of recurrent pancreatic and prostate cancers. PLDR IMRT is an effective treatment choice for recurrent cancers in most cancer centers.