2Department of Physics, V.B.S. Purvanchal University, Prof. Rajendra Singh (Rajju Bhaiya) Institute of Physical Sciences for Study and Research, Jaunpur-India DOI : 10.5505/tjo.2025.4496 OBJECTIVE
The study objective was to assess the dosimetric and radiobiological characteristics of flattened filter (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.