Epidemiologic evidence for the role of indoor tobacco smoke as an initiator of human breast carcinogenesis.

Earlier research suggested an appreciable latent period between the time of exposure to indoor tobacco smoke and the detection of breast cancer. A close relationship was found in the U.S. between state breast cancer mortality from 1978 through 1981 and state cigarette sales from 1950 through 1954 (R = 0.64, p less than 0.001). The correlation declined for sales in subsequent years but remained highly significant until 1970, but not thereafter. Thus, it appears that the role of indoor tobacco smoke in breast carcinogenesis is that of an initiator and/or an early-stage promoter in the process that leads after 15 to 30+ years to cancer. Trends in cigarette consumption from 1915 to 1965 paralleled breast cancer incidence in Connecticut women from 1935 to 1989. The 1953 and 1975 peaks in incidence were related to 1930 and 1953 peaks in cigarette consumption, respectively, showing a 22.5-year latent period. The drop in cigarette sales in the mid-1950s was followed by a surge to new highs in sales in the early 1960s in the great majority of the states. Approximately 23 years later, breast cancer incidence rates in the mid-1980s in all nine SEER populations are reflecting that surge in cigarette sales, rising to an all-time high in 1985. The earliest declines in breast cancer incidence should occur in New York and Connecticut, where cigarette sales have fallen most dramatically. By the year 2015, white women in the South, currently living with the men with the highest lung cancer rates in the U.S., are expected to show the highest breast cancer rates in the country.