Comparative Dosimetric and Radiobiological Evaluation of Dental Structures and Normal Tissue Complication Probability

Head and neck cancers require highly conformal radiotherapy techniques to achieve optimal tumor control while minimizing damage to the surrounding critical structures. The present study aimed to compare advanced radiotherapy planning techniques with an emphasis on dental structures and radiobiological outcomes.

This retrospective observational dosimetric study was conducted on radiotherapy planning records of 25 patients treated over a 10-year period with head and neck malignancies. For each patient, two radiotherapy plans were generated on the same computed tomography dataset using identical optimization parameters. Target volumes and organs at risk (OAR), including the dental structures, parotid glands, mandible, and spinal cord, were contoured. Dose-volume histogram parameters, such as the mean dose, maximum dose, and volume-based indices, were analyzed. Radiobiological evaluation was performed using normal tissue complication probability (NTCP) modeling for xerostomia and mandibular osteoradionecrosis. Statistical analysis was performed using paired tests with a significance level of less than 0.05.

Both techniques achieved comparable target volume coverage; however, significant improvements in plan quality were observed with the arc-based delivery. The conformity index was higher (0.87 ± 0.04 versus 0.82 ± 0.05; p < 0.001), and the homogeneity index was improved (0.078 ± 0.015 vs. 0.091 ± 0.018; p < 0.001). Mean dose to the parotid glands was significantly reduced (24.6 ± 3.8 gray versus 29.8 ± 4.2 gray; p < 0.001). Dental structures demonstrated lower mean dose (30.4 ± 8.1 gray versus 36.1 ± 8.9 gray; p = 0.002) and reduced volume receiving 30 gray (40.8 ± 13.1% versus 50.4 ± 14.2%; p = 0.001). The mandibular dose parameters were also significantly reduced (p = 0.001). Radiobiological analysis showed a significant reduction in predicted xerostomia (27.3 ± 9.8% versus 38.4 ± 11.6%; p < 0.001) and mandibular osteoradionecrosis (5.2 ± 3.9% vs. 8.7 ± 5.4%; p < 0.001).

Advanced radiotherapy planning techniques provide superior dose conformity, improved sparing of dental structures and OAR, and a significant reduction in predicted complication probabilities. These findings support their clinical use for optimizing treatment outcomes and improving the long-term quality of life in patients with head and neck cancer.