A comparison of treatment plans using linac-based intensity-modulated radiation therapy and helical tomotherapy for maxillary sinus carcinoma

This study evaluated whether helical tomotherapy (TOMO) planning could achieve better isodose distribution for the maxillary sinus while concomitantly sparing the adjacent critical normal organs than linac-based step-and-shoot IMRT (s-IMRT) planning. TOMO and s-IMRT were established for 10 patients with maxillary sinus cancer. The prescription (66 Gy, 30 fractions) was used to cover the planning target volume (PTV) with a 95% isodose line. Each plan was independently optimized using the CORVUS planning system and Tomotherapy Hi-Art system. The treatment plans were compared using dose volume histogram (DVH), a dose homogeneity index (DHI) of the PTV, and equivalent uniform dose (EUD) and DVH of organs at risk (OARs). The TOMO plans demonstrated better dose homogeneity compared to the s-IMRT plans. The average V95% of the TOMO plans was similar to that of the s-IMRT (92.92% vs. 95.07%, respectively), but the average V107% was 0% for TOMO compared with 18.74% for s-IMRT. The average maximum dose reduction was 7 Gy, and DHI increased by 8% for PTV1 in TOMO compared with s-IMRT (79 Gy vs. 71 Gy and, 89% vs. 97%, respectively). The average EUD reduction for the optic nerve was 17%. In summary, planning with TOMO was superior to s-IMRT planning with respect to dose homogeneity within the PTV and sparing of the optic nerve.