Dosimetry evaluation of salivary glands in 3D conformal radiotherapy and intensity modulated radiotherapy in oral tongue cancer

The purpose of this study was to evaluate the dosimetric and radiobiological parameters of salivary glands in treatment of patients with oral tongue cancer by 3D conventional radiotherapy (3D-CRT) and intensity modulated radiation therapy (IMRT) techniques.

This study was performed on treatment planning of patients with oral tongue cancer in T2-3/N0 cancer staging. In this way, the treatment planning was performed on CT images for 3D-CRT and IMRT techniques (with 5, 7 and 9 fields) for all patients. Then, the homogeneity (HI) and conformity index (CI) of dose in the target volume and maximum, mean does of the salivary glands and normal tissue complication probability of parotid glands were computed and compared between different treatment.

Results of this study indicated an increase in HI and CI in IMRT compared to 3D-CRT (up to 61.54% and 28.78%). Moreover, the increase in the number of beams in the IMRT technique can lead to decrease in the mean dose of sublingual glands (up to 9.52%) and decrease in the maximum dose of the submandibular glands (up to 6.93%), while, the use of IMRT with 5 and 7 beams can lead to a significant increase in the probability of xerostomia in parotid gland (up to 8.61%) compare with 3D-CRT technique.

It can be concluded that IMRT technique with 9 fields led to improve the salivary glands protection, more homogeneity and conformity in the target volume and reducing the received dose of submandibular and sublingual glands compare to the 3D-CRT in patient with oral tongue cancer.