Dosimetric comparison of stereotactic MR-guided radiation therapy (SMART) and HDR brachytherapy boost in cervical cancer
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The standard of care in locally advanced cervical cancer (LACC) is concomitant chemoradiotherapy followed by high-dose-rate brachytherapy (HDR-BT). Although previous studies compared HDR-BT with stereotactic body radiotherapy (SBRT), there is scarce data regarding the dosimetric outcomes of stereotactic MR-guided adaptive radiation therapy (SMART) boost in lieu of HDR-BT. In this single-institutional in-silico comparative study, LACC patients who were definitively treated with external beam radiotherapy followed by HDR-BT were selected. Target volumes and organs at risk (OARs) were delineated in MRI and HDR-planning CT. An HDR-BT and a SMART boost plan were generated with a prescribed dose of 28 Gy in four fractions for all patients. The HDR-BT and SMART boost plans were compared in regard to target coverage as well OARs doses. Mean EQD2 D90 to HR-CTV and IR-CTV for HDR-BT plans were 89.7 and 70.5 Gy, respectively. For SMART, the mean EQD2 D90 to HR-PTV, HR-CTV, and IR-CTV were 82.9, 95.4, and 70.2 Gy, respectively. The mean D This dosimetric study demonstrates that SMART can be applied in cases where HDR-BT is not available or ineligible with acceptable target coverage and OAR sparing. However, prospective clinical studies are needed to validate these results.