A wide-ranging search for benign and malignant tumors of the major and minor salivary glands among members of the Life Span Study sample of the Radiation Effects Research Foundation identified 41 malignant and 94 benign incident tumors, including 14 malignant and 12 benign tumors of the minor salivary gland, plus 10 major gland tumors of unknown behavior. Dose-response analyses found statistically significant increases in risk with increasing A-bomb dose for both cancer and benign tumors. Estimated relative risks at 1 Sv weighted tissue kerma (RR1Sv, with 90% confidence interval in parentheses) were 4.5 (2.5-8.5) for cancer and 1.7 (1.1-2.7) for benign tumors. When analyzed by histological subtype within these two broad groups, it appeared that most of the dose response for malignant tumors was provided by an exceptionally strong dose response for mucoepidermoid carcinoma [11 exposed cases with dose estimates, RR1Sv = 9.3 (3.5-30.6)], and most or all of that for benign tumors corresponded to Warthin's tumor [12 cases, RR1Sv = 4.1 (1.6-11.3)]. There was a marginal dose response for malignant tumors other than mucoepidermoid carcinoma [RR1Sv = 2.4 (0.99-5.7)] but no significant trend for benign tumors other than Warthin's tumor [RR1Sv = 1.3 (0.9-2.2)]. Re-examination of the original data from published studies of other irradiated populations may shed new light on the remarkable type specificity of the salivary tumor dose response observed in the present study.

METHODS.certained from the tumor and tissue registries of Hiroshima and Nagasaki and 1 Consultant, Radiation Effects Research Founsupplemented by additional case findings from autopsy, biopsy, and surgical specidation, Hiroshima and Nagasaki, Japan.mens maintained at RERF and other institutions. Pathology slides and medical documents were reviewed by a panel of four pathologists who classified tumors

These findings, supported by population-based analyses in a companion study reported elsewhere, suggest a causal role for ionizing radiation in salivary gland tumorigenesis, particularly for mucoepidermoid carcinoma, and in the induction of one type of benign tumor (Warthin's tumor).