Serum amylase and tissue polypeptide antigen as biochemical indicators of salivary gland injury during iodine-131 therapy.

The study evaluated the possibility of using serum alpha-amylase and tissue polypeptide antigen (TPA) as biochemical markers of radiation injury in the salivary gland of patients with thyroid carcinoma treated with iodine-131. The results demonstrated that the two molecules increased 1 day after 131I administration and returned to near control values on the 3rd day. The increase was greater and longer lasting in those patients treated with the higher 131I administered activity. However, when the patients were divided into groups based on recovery time, which determined patients with different radionuclide elimination rates, the increase in the two molecules was greater and more lasting in those subjects with a longer period of hospitalization. A comparison with the values obtained from patients with tumours of the head and neck treated with external radiotherapy demonstrated that after the 1st day of treatment the salivary gland received an absorbed dose which, based on alpha-amylase levels, ranged between 0.24 and 1.89 Gy and, based on TPA levels, between 0.28 and 2.29 Gy.