Dose optimization for the treatment of anaplastic thyroid carcinoma: A comparison of treatment planning techniques

Purpose: To evaluate and compare dose optimization for the treatment of ana plastic thyroid carcinoma using a 3D conformal plan, and two 3D intensity-m odulated inverse plans. Methods and Materials: After patient immobilization using an alpha cradle a nd head-mask system, a postoperative CT scan was obtained to delineate the gross tumor volume (GTV), the clinical tumor volume (CTV), and adjacent cri tical structures. Treatment plans were generated using UM-Plan (University of Michigan), Peacock-Plan and Corvus (NOMOS Corporation, Sewickley, PA). I sodoses were displayed in the sagittal, coronal, and multiple axial planes, and dose-volume histograms (DVH) were generated for the GTV, CTV, and crit ical normal tissues. Treatment times were estimated to compare the practica lity of delivering each plan in a busy radiotherapy department. Results: All three treatment planning systems were able to deliver a minimu m dose of 60 Gy to the GTV while keeping the maximum spinal cord dose at or below 45 Gy, However, there were differences in the doses delivered to 50% and 5% of the cord, the minimum CTV dose, and the overall treatment time. The PeacockPlan best spared the uninvolved tissues of the posterior neck, a nd provided the lowest dose to the cord without compromising the CTV. Conclusions: Inverse treatment planning provides superior dose optimization for the treatment of anaplastic thyroid carcinoma. The radiobiologic impac t of intensity modulation for this tumor should be further tested clinicall y. (C) 2000 Elsevier Science Inc.