Comparison of 3D conformal and intensity modulated radiotherapy in early stage oral tongue cancer: dosimetric and radiobiological evaluation

Background: The aim of this study was to compare the dosimetric and radiobiological efficiency of various intensity modulated radiotherapy (IMRT) techniques with 3D conventional radiotherapy (3D-CRT) technique in the treatment of early stage oral tongue cancer. Materials and Methods: This study was performed on 38 CT images of patients who were planned with 3D-CRT and three sets of IMRT treatment plans including five, seven and nine fields with prescribed dose of 66 Gy to planning target volume. The dose volume histograms, homogeneity index (HI), conformity index (CI) and normal tissue complication probability (NTCP) of main organs at risk were derived using Prowess Panther treatment planning system. Results: The results of this study indicated an increase in HI and CI for IMRT plans compared to 3D-CRT. Furthermore, IMRT techniques led to a statistically significant reduction in received dose by mandible (up to 10.10 Gy) and thyroid (up to 13.59 Gy) compared to the conventional technique used; whereas, it led to a statistically significant increase in received dose by parotid glands (up to 7.62 Gy) and brain stem (up to 9.87 Gy). In addition, IMRT increased (up to 12.79%) the probability of occurrence of parotid xerostomia and decreased mandibular complications (up to 7.76%) in comparison to conventional treatment. Conclusions: It can be concluded that IMRT can be more successful in improving oral tongue cancer treatment with more conformity and homogeneity. However, IMRT may not be required for all patients with oral tongue cancer at early stage of the disease.