SU‐FF‐T‐149: Conformal Vs. IMRT Concomitant Boosts for IMRT Based Head and Neck Treatment

Abstract

Purpose: To evaluate conformal 3D‐CRT and IMRT techniques for the boost portion of a concomitant boost treatment schedule for IMRT based head and neck radiation. Method and Materials: Nine‐field IMRT plans were generated using Eclipse for 4 stage IV oropharynx patients, treating all target volumes initially to 57Gy. Two alternative plans were then generated to deliver a 15Gy boost to gross disease: a 3D conformal plan, using 3–4 fields, and 5‐field IMRT plan. Boost volumes ranged from 25–60cc. The IMRT and 3D‐CRT boost plans were evaluated as individual graphic plans and as a cumulative with the first course treatment for a total dose of 72Gy (IMRT/IMRT and IMRT/3D‐CRT combinations). The comparison assessed target coverage, dose to critical structures (parotids, cord and oral cavity), hot spots and number of monitor units (MU). Results: Evaluated as a cumulative plan the IMRT/IMRT technique met all the constraints for critical structures (mean dose to parotid 26Gy, cord max 46Gy) and the hot spots were between 104–106%. The IMRT/3D conformal technique also met the constraints for the critical structures with hot spots between 103–105%. Both cumulative plans achieved 98.6–100% coverage of boost volumes. Evaluated as individual plans both the IMRT and 3D conformal boost plans achieved the desired coverage while keeping the dose to critical structures at a minimum; hot spots were located within the confines of the boost volume. The number of MU's ranged from 250–296 for the 3D‐CRT plan in comparison to 360–562 for the IMRT. Average planning time was 1.0 and 2.5 hours for the IMRT and 3D‐CRT boost, respectively. Conclusion: Both boost techniques are dosimetrically equivalent. Treatment technique can therefore be chosen based on the available clinical recourses.