Quantitative estimation of doses to salivary glands from using brachytherapy in head and neck cancers

To quantify the percentage doses received by salivary glands (SGDs) in head and neck interstitial brachytherapy (BT).

The study included 43 patients who underwent high-dose rate iridium-192 implant for oral cavity and oropharyngeal lesions treated with BT as a boost. BT dose varied with disease stage and external radiation dose, with the total mean dose of 66±4Gy. Patients were divided into two groups, midline and lateralized, based on anatomic implant location. Different dose parameters such as D(max), D(mean), DV(30%) of individual glands were derived from dose volume histogram representing the percentage maximum dose, mean dose, and dose received by 30% volume of individual SGDs, respectively. For better perception of the impact of BT on individual SGDs, the doses received are extrapolated to radical BT dose of 60Gy.

For lateralized implants, the highest dose received by ipsilateral parotid (PTD) was 12.3% seen in tonsillar implants. The contralateral PTD receives minimal doses. As expected, the ipsilateral submandibular gland (SMG) received high doses in the range of 80% of the total prescribed dose, whereas contralateral SMG received 10% of ipsilateral dose. For the midline implants, the mean dose range for PTD was 7-11% of the total prescribed dose and for SMG between 17% and 56%, depending on the location.

The study quantifies the percentage doses received by the individual SGDs in interstitial head and neck BT for use in future planning of the BT procedures and for salivary functional studies, prediction of damage, and quality-of-life parameters.