Dosimetric comparisons of three-dimensional conformal radiotherapy, intensity-modulated radiotherapy, and helical tomotherapy in whole abdominopelvic radiotherapy for gynecologic malignancy

Objectives. The goal of this study was to dosimetrically compare 3-dimensional radiotherapy (3DCRT), intensity-modulated radiotherapy (IMRT), and helical tomotherapy (TOMO) plans for whole abdominopelvic radiotherapy (WART) in patients with gynecologic cancer. Methods. Ten patients were selected for WART planning. Doses were prescribed to planning target volumes (PTVs) as the followings: 30 Gy to PTV-whole abdominopelvis (PTV-WA), 40 Gy to PTV-para-aortic lymph node (PTV-PALN), 44 Gy to PTV-pelvis, and 50 Gy to gross target volume (GTV) in 20 fractions. Dose to whole liver, both kidneys, and spinal cord were constrained below each tissue tolerance, and bone marrow (BM)-sparing technique was adopted in IMRT and TOMO. Dosimetric parameters and treatment times were compared among plans. Results. Calculated doses in TOMO came most closely to the prescribed dose for coverage of PTV-WA, PTV-PALN, PTV-pelvis, and GTV compared to 3DCRT, and IMRT. In normal organs, TOMO had significantly better dosimetric profiles compared to IMRT and 3DCRT. TOMO significantly reduced V20Gy, and mean dose of whole liver, both kidneys, and spinal cord. The use of BM-sparing technique (BMS) did not impair coverage of target volume in IMRT and TOMO. While IMRT showed no differences of irradiated BM dose using BMS, TOMO with BMS reduced half V20Gy of BM compared to TOMO without BMS. Conclusions. TOMO showed dosimetric superiority in target coverage, sparing BM, and other normal organs compared to 3DCRT and IMRT. Clinical experiences will be needed for evaluation of feasibility of WART using TOMO in patients with gynecologic cancer.