Qingyi Wei, MD, Ph.D.
Background: Salivary glands have been shown in previous research to be highly sensitive to radiation exposure. Exposure to gamma radiation (ie. X-rays) is a known risk factor for both benign and malignant salivary gland tumors. However, the precise mechanism for this adverse effect has not been determined. The focus of this study was to determine whether radiation-induced chromosome breaks are a risk factor for benign and malignant tumors and whether there were any differences in risk between the two types of tumors.
Advance: The authors performed a pilot case-control study of 57 salivary gland cancer patients and 105 controls with no history of salivary gland cancer. Blood lymphocytes were collected and cultured from all research participants. The blood cells were exposed to a single dose of gamma radiation. Five-hours later, slides of the exposed cells were prepared so that counts of chromosome breaks could be determined. There were highly significant increases in the number of breaks/cell from the lymphocytes of the salivary cancer patients. The patients with malignant salivary gland tumors were 40 times more likely to have breaks/cell values higher than the median of the controls. Patients with benign tumors were less likely (4.7 times) to have elevated breaks/cell as compared to the controls.
Implication: Although this study was small and needs to be confirmed in larger studies, it does show that exposure to gamma radiation is a likely risk factor for malignant and benign salivary tumors. If larger studies do indeed confirm these results, this finding could have public health implications regarding the frequency of use of gamma radiation in the practice of dentistry.
Citation: Zheng R, Wang LE, Bondy ML, Wei Q, Sturgis EM. Gamma radiation sensitivity and risk of malignant and benign salivary gland tumors: a pilot case-control analysis. Cancer. 2004 Feb 1; 100(3):561-7