Lowering the radiation dose to the submandibular gland of patients with head and neck cancer decreases xerostomia, according to a study presented on April 20 at the European Society for Radiotherapy and Oncology (ESTRO) meeting in Geneva.
Radiation oncologists at University Medical Center Utrecht (UMCU) showed for the first time that it is possible to reduce xerostomia in patients treated with radiotherapy for head and neck cancer if the radiation dose to a salivary gland (the submandibular gland) on the opposite side to the tumor is minimized, stated a university press release.
It is the largest study yet to show a correlation between radiation doses to the submandibular glands and their output of saliva. Guidelines for the recommended maximum dose could potentially be issued for use in clinical practice to benefit patients, according to the researchers.
Approximately 40% of head and neck cancer patients suffer from xerostomia in the long term, which causes problems with eating, sleeping, speech, tooth loss, and oral hygiene, leading to diminished quality of life, social isolation, and difficulty in the ability to work. Attempts to treat xerostomia and its consequences can be costly and are not very effective, the study noted.
Therefore, the UMCU researchers looked at using intensity-modulated radiotherapy (IMRT) to treat the tumors and spare the submandibular gland on the opposite side of the tumor and both parotid glands. They also wanted to determine the maximum radiation dose and how the treatment would affect patients' xerostomia.
They analyzed 50 patients with throat cancers in which cancer cells had not migrated into the contralateral lymph nodes and had not metastasized to other parts of the body. The patients were treated with the contralateral submandibular IMRT and compared with a historical group of 52 patients who had received radiotherapy that had spared only the parotid glands.
After six weeks and after one year, the researchers measured saliva flow objectively from the submandibular and parotid glands by stimulating saliva with citric acid on the tongue and catching the resulting saliva in specially designed cups. They also used a questionnaire to measure the patients' subjective experience of xerostomia.
Saliva flows from the contralateral submandibular glands were significantly higher at six weeks and at one year in patients who received a dose to the submandibular gland of less than 40 Gy, which translated into fewer complaints of xerostomia, the researchers reported. Using the new technique, they were able to keep the dose to less than 40 Gy in half of the patients.
All but one of the patients who could be treated with radiation doses of less than 40 Gy to the submandibular gland had small tumors (less than 4 cm in diameter). These patients consequently had fewer problems with xerostomia after a year.
The study could lead to guidelines recommending a maximum dose of 40 Gy for the submandibular gland, the researchers noted.
