During the period 1970-1989, age-adjusted mortality rates for lung cancer in Italy increased by more than 50%, while rates for larynx cancer in males decreased by approximately 13%. This study aims to interpret this difference, which seems to contradict the finding that cigarette smoking is a common major risk factor for both lung and larynx cancer. To this end, we jointly analyzed the time trends of incidence, survival and mortality. We first examined survival data taken from the population-based Lombardy Cancer Registry (northern Italy). Based on data referring to 860 incident cases of larynx cancer, diagnosed during the period 1976-1987, we estimated a 3% annual increase in relative survival. By contrast, no significant period effect was observed for survival rates of 2,259 incident cases of lung cancer.
National incidence rates were estimated using official mortality data and the above-described survival data. Age-adjusted estimated incidence rates increased, from 1970 to 1989, for both cancer sites: +55% for male lung, +56% for female lung, and +22% for male larynx. Moreover, the patterns of birth-cohort effect, which are diverging for mortality, are nearly parallel with regard to incidence. This analysis suggests that a substantial improvement in survival of larynx cancer patients may largely explain the differences in mortality trends for cancer of lung and larynx. © 1994 Wiley-Liss, Inc.