Volumetric Modulated Arc Therapy versus Fixed-Field Intensity-Modulated Radiotherapy in Radical Irradiation for Cervical Cancer without Lymphadenectasis: Dosimetric and Clinical Results.

BACKGROUND: The aim of this study was to compare the dosimetric parameters, clinical complications, and efficacy of volumetric modulated arc therapy (VMAT) and fixed-field intensity-modulated radiotherapy (f-IMRT) in radical radiotherapy for cervical cancer without lymphadenectasis. METHODS: 84 cervical cancer patients undergoing treatment with VMAT and f-IMRT were selected. Dose-volume histograms were used to evaluate the dose distribution in the planning target volume (PTV) and organs at risk. The clinical complications and efficacy were observed. RESULTS: The homogeneity index (HI) and the conformity index (CI) of VMAT plans were both superior to the HI and CI of f-IMRT plans (p = 0.043, 0.025). VMAT plans resulted in a reduction in the V30 of the rectum and V40 of the bladder (p = 0.002). Furthermore, the monitor units (MUs) for VMAT were less than a quarter of those for f-IMRT. The treatment time for VMAT was less than a half of that for f-IMRT. Both clinical complications and efficacy showed no significant differences. CONCLUSION: VMAT plans showed superior dose coverage of the PTV, better protection of the rectum and bladder in dosimetry, and significantly reduced MUs and treatment time compared with f-IMRT. Clinical results were similar for both plans.

Dosimetric comparison of helical tomotherapy, VMAT, fixed-field IMRT and 3D-conformal radiotherapy for stage I-II nasal natural killer T-cell lymphoma.

BACKGROUND: The aim of this study was to compare radiotherapy plans for Stage I-II nasal natural killer/T-cell lymphoma (NNKTL) using helical tomotherapy (HT), volumetric-modulated arc therapy (VMAT), Fixed-Field intensity-modulated radiotherapy (IMRT), and three-dimensional conformal radiotherapy (3D-CRT). METHODS: Eight patents with Stage I-II NNKTL treated with IMRT were re-planned for HT, VMAT (two full arcs), and 3D-CRT. The quality of target coverage, the exposure of normal tissue and the efficiency of radiation delivery were analyzed. RESULTS: HT showed significant improvement over IMRT in terms of D98%, cold spot volume and homogeneity index (HI) of planning target volume (PTV). VMAT provided best dose uniformity (p = 0.000) to PTV, while HT had best dose homogeneity among the four radiotherapy techniques (p = 0.000) to PTV. VMAT obviously reduced treatment time (p = 0.010; 0.000) compared to HT and IMRT. Mean dose of left and right optic nerve was significantly reduced by IMRT compared to HT (19.86%, p = 0.000; 21.40%, p = 0.002) and VMAT (8.97%, p = 0.002; 9.35%, p = 0.001), and maximum dose of left lens of VMAT increased over the HT (36.25%, p = 0.043) and IMRT (40.65%, p = 0.001). CONCLUSION: The unexpected results show that both HT and VMAT can achieve higher conformal treatment plans while getting worse organs at risk (OARs) sparing than IMRT for patients with Stage I-II NNKTL. VMAT requires the shortest delivery time, and IMRT delivers the lowest dose to most OARs. The results could provide guidance for selecting proper radiation technologies for different cases.