Background: This study used data from the population-based Connecticut Tumor Registry, a unique resource for examining secular trends in cancer incidence rates since 1935.
Methods: Trends in average annual age-standardized incidence rates (ASRs) for invasive cancers in Connecticut residents were examined from 1935-1939 to 1990-1991.
Results: Trends in ASRs were complex, with some sites showing large increases but others only small changes since 1935-1939. Declines were evident for stomach and cervical since 1935-1939 and for colorectal cancer after 1980-1984. Since 1965-1969, when 2% or less of cancers were ascertained only by death certificates, exclusion of cancers of the breast and prostate (strongly affected by increased screening), smoking-related cancers, and cancers of other sites with identified causes (melanoma and human immunodeficiency virus-related cancers), resulted in little or no increase in the ASRs for all other sites combined. For young (20-44-year-old) adults, unexplained increases since 1965-1969 were limited to testicular cancer and Hodgkin's disease.
Conclusions: Reducing cancer incidence rates will require expanded primary prevention efforts (mainly involving behavioral changes) and more etiologic research on common cancers whose causes are poorly understood (e.g., breast and prostate cancer) and rarer cancers showing unexplained recent increases (i.e., testicular cancer and Hodgkin's disease).