MUKESH ZOPE, DEEPALİ PATIL, DEVRAJ SINGH
Turkish Journal of Oncology - 2025;40(2):120-132
OBJECTIVE The study objective was to assess the dosimetric and radiobiological characteristics of flattened fitler (FF) and flattening filter-free (FFF) beam techniques in volumetric modulated arc therapy (VMAT) for patients with postoperative oral cavity cancer. METHODS 20 patients with oral cavity cancer underwent treatment for VMAT_FF. Subsequently, retrospective VMAT_FFF treatment plans were developed using the eclipse treatment planning system. Both treatment plans adhered to a Simultaneous Integrated Boost (SIB), delivering 60Gy to PTV60 and 54Gy to PTV54 in 30#. The assessment encompassed biological indices (e.g., NTCP) and physical dose metrics, including target coverage, conformity, dose homogeneity, and doses to organs at risk. RESULTS The dosimetric evaluation revealed negligible differences between the both techniques. The conformity index was similar for VMAT_FF (0.975±0.017) and VMAT_FFF (0.975±0.019, p=0.813). The monitor units required for VMAT_FFF (583±52.1) were significantly greater than VMAT_FF (530±69.9, p=0.001). NTCP values for critical structures, including the spinal cord, brainstem, and optic chiasm, were consistent at 0.00±0.00 for both techniques. For the parotid glands, NTCP values related to xerostomia show insignificant variation: 17.8±8.17 (right) and 20.3±11.2 (left) for VMAT_FF compared to 17.9±8.29 (right) and 20.7±11.4 (left) for VMAT_FFF. CONCLUSION Both VMAT_FF and VMAT_FFF techniques exhibited comparable dosimetric and radiobiological results for the treatment of oral cavity cancer. Although VMAT_FFF required a higher number of monitor units, it demonstrated similar clinical effectiveness, suggesting its appropriateness for therapeutic application.
