Aim: This study aimed to compare the response, dosimetric parameters and toxicities of IMRT with Flattening Filter(FF) photon beam and Flattening Filter Free(FFF)photon beam in Oral Cavity cancers.

Material and Methods-This study was conducted as prospective observational study on total of 60 cases of oral cavity cancerat our institute during study period of 2 years. All 60 participants were randomly assigned into either of the two treatment group IMRT-FF and IMRT-FFF.Patients were followed and assessment of dosimetric parameters, response and toxicities grading was done.

Results- Two groups were comparable with respect to baseline variables and tumor characteristics and treatment (p>0.05).  Mean number of fractions, as well as dose to brainstem, spinal cord and parotid were significantly higher in FF group as compared to FFF group (p<0.05). The response rate following radiation was found to be significantly better in FFF group as compared to FF group (p<0.05). Skin toxicities were significantly higher in FFF group at 3 months (p<0.05) whereas parotid as well as oral cavity were significantly higher in FF group at 3 and 6 months (p<0.05).

Conclusions-Intensity Modulated Radiation Therapy (IMRT) is common modality used for management of oral cavity cancer. FF photon beam and FFF photon beam, both modalities were compared in this study and we found that removal of flattening filter helps in equivalent delivery of dose of radiation to target tissue, with reduced scattering and leakage of radiation dose to adjacent normal tissues thereby reducing the risk of toxicities of organ at risks.