Volumetric-modulated arc therapy versus intensity-modulated radiotherapy for localized prostate cancer: a dosimetric comparative analysis of moderate hypofractionated radiation

Aim: To compare Intensity Modulated Radiotherapy (IMRT) and Volumetric-Modulated Arc Radiotherapy (VMAT) for patients receiving moderate hypofractionated radiotherapy. Introduction: Hypofractionated radiation has been established for localized prostate cancer; however, eligibility for this treatment depends on strict dosimetric constraints. Methods: CT simulation datasets of 23 patients with localized prostate adenocarcinoma were analysed, IMRT and VMAT plans were generated for each patient. Dose Volume Histogram (DVH) records, Monitor Units (MUs), treatment delivery times, conformality, and homogeneity indices were compared between the two techniques. Hypofractionated regimen parameters were assessed for each technique to evaluate plan eligibility for the short-course radiotherapy (60 Gy over 20 fractions). Results: Compared with IMRT plans, VMAT resulted in better PTV coverage (p=0.001) and significantly decreased bladder and rectal (D50) doses (p=0.019 and p=0.002, respectively). Both conformality and homogeneity were improved with VMAT but did not reach statistical significance. The mean MUs were lower with VMAT than with IMRT (662 vs 738). Moreover, the treatment time was shorter with VMAT than with IMRT (mean, 1.8 vs 7.1 minutes, p= 0.004). Four IMRT plans did not meet hypofractionated objectives and were deemed not eligible for short-course radiotherapy. All VMAT plans met the planning objectives. Conclusion: For hypofractionated prostate irradiation, VMAT resulted in improved PTV (D99) coverage and more sparing of surrounding tissues. VMAT used less MUs and shorter treatment time. VMAT could meet all constraints and made patients eligible for hypofractionated radiotherapy. Therefore, VMAT may be preferred for patients who undergo moderate hypofractionation scheme.