Scintigraphic assessment of salivary dysfunction after radiation therapy using CT simulation technique in patients with head and neck cancers

Radiation therapy using CT simulation technique can provide shielding for normal tissue and significantly reduce radiation-induced xerostomia in head and neck cancer patient(pt)s. The aim of this study was to assess the salivary dysfunction after radiation therapy in pts with head and neck cancer and to evaluate the salivary shielding effect of CT simulation technique by salivary scintigraphy. Fifteen pts (mean age: 48±15) who had been irradiated to head and neck for various malignancies (papillary thyroid cancer: 5, nasopharyngeal cancer: 4, lymphoma: 3, other: 4) underwent salivary scintigraphy with Tc-99m pertechnetate before and 4-6 months after radiation theraphy (mean interval: 158±33 days). The mean neck radiation dose was 58±11 cGy. Ten salivary glands (9 parotid glands, 1 submandibular gland) were shielded from radiation (less than 30 cGy of mean dose in 80% volume of gland). Using salivary scintigraphy, secretory function (uptake20; glandular uptake at 20 minute/ background uptake) and excretory function (EF: %washout after stimulation of orange juice) of each glands were obtained. Fifty seven salivary glands were analyzed. In irradiated glands (n=47), the EF values of both parotid and submanidibular glands were significantly, decreased compared with before radiation (59.3±26.4 vs 15.9±28.4, 56.6±22.9 vs 12.6±21.9 respectively, p<0.005) and the uptake20 values of both parotid and submandibular glands were also significantly decreased after radiation (4.0±1.8 vs2.4±0.9, p<0.001, 5.3±1.9 vs 4.2±1.4, p<0.05). The uptake20 and EF values of shielded glands before and after radiation therapy showed no significant difference (3.9±1.9 vs 3.9±2.4, 56.97±27.8 vs 55.9±28.5, respectively). In radiation therapy of head and neck cancer, salivary dysfunction can be prevented using radiation shield by CT simulation technique. Salivary scintigraphy is a useful non-invasive tool for quantitative assessment of radiation-induced salivary dysfunction and shielding effect