Dosimetric comparison of 3-dimensional conformal radiotherapy (3D-CRT) and volumetric-modulated arc therapy (VMAT) in locally advanced cancer cervix

Introduction:Dosimetric advantages of volumetric-modulated arc therapy (VMAT) over three-dimensional conformal radiotherapy (3D-CRT) are not established in a head-on comparison of a uniform group of locally advanced carcinoma of the cervix (LACC). Therefore, we conducted a dosimetric comparison of these two techniques in LACC patients. Materials and methods:Computed tomography (CT) data of histologically proven de novo LACC, including Stage IIB-IIIB and earlier stages deemed inoperable, were included in this prospective observational dosimetric study. Planning was initially done by 3D-CRT technique (dose of 45-50 center dot 4 Gy @ 1 center dot 8-2 Gy/# was used in the actual treatment), followed by VMAT planning and appropriate dosimetric comparisons were done in 39 cases. Results:For planning target volume coverage, D-95, D-98 and D-100 (p < 0 center dot 0001 for all parameters) and V-95 and V-100 (p = 0 center dot 002 and <0 center dot 0001, respectively) were significantly improved with VMAT. The conformity index (CI) was significantly better with VMAT (p = 0 center dot 03), while 3D-CRT had a significantly better homogeneity index (HI)(p = 0 center dot 003). Dose to the urinary bladder was significantly reduced with VMAT compared to 3D-CRT for V-20-V-50, except V-10. The doses to the rectum and abdominal cavity were significantly reduced with VMAT compared to 3D-CRT plans for all parameters (V-10-V-50). The number of organs at risks (OARs) for which constraints were met was higher with VMAT plans than with 3D-CRT plans, with at least four out of the five OARs protected in 46 center dot 1 versus 5 center dot 1% and all constraints achieved in 15 center dot 4% versus none. Conclusion:We conclude that in dosimetric terms, VMAT is superior to 3D-CRT for LACC.