Recent trends in the incidence of salivary gland cancer.

Beginning in 1985, a sudden and sustained doubling of salivary gland cancer incidence, among men only, is observed in the San Francisco-Oakland Metropolitan Statistical Area. Registry data are examined to determine the nature of this increase and its possible association with the AIDS epidemic. Changes in patient characteristics are assessed by comparing their distribution among recently diagnosed cases (1985-1988) to an expectation based on population growth and the age-specific incidence among patients diagnosed earlier (1973-1984). Based on the observed patterns, it is unlikely that the temporal increase in these tumours is a direct result of the AIDS epidemic or solely the result of a shift in the prevalence of established risk factors. The increase is predominantly seen in men over the age of 75 at diagnosis (O/E = 2.3, p = 0.02) and is observed among both those with and without a prior cancer (O/E = 2.7, p = 0.02 and O/E = 1.5, p = 0.06, respectively). Radiation for the prior cancer was not associated with increased occurrence. Military exposure is crudely approximated by examining birth cohorts. However, the cohort data do not support a hypothesis of military exposure.