Study: Less smoking leads to less lung cancer

A new American Cancer Society study finds that, by even a conservative estimate, reductions in smoking accounted for about 40 percent of the decrease in cancer-death rates among men between 1991 and 2003.

The study, published Tuesday in the journal Tobacco Control, is the first to systematically address the dramatic impact of tobacco-control efforts over the last 40 years or so on cancer-death rates.

According to the society, the age-adjusted overall U.S. cancer-death rate peaked in 1991. Between 1991 and 2003, the mortality rate from cancer dropped by 16.1 percent in men and 8.4 percent in women.

"The greater decline in cancer-death rates among men is due in large part to their substantial decrease in tobacco use. We need to enhance efforts to reduce tobacco use in women so that the rate of decline in cancer-death rates becomes comparable to that of men," said Betsy Kohler, president of the North American Association of Central Cancer Registries, who was not involved in the study.

The decrease in lung cancer and overall cancer mortality among men began about 30 years ago after a downturn in their smoking rates. No decrease in lung-cancer mortality has yet occurred among women, who generally took up regular smoking 20 to 30 years after men and have been slower to stop smoking. Lung cancer remains the leading cancer killer for men and women.

Overall U.S. smoking rates fell by half between the mid-1960s and the mid-'90s, to about 27 percent of adults, and about 22 percent of adults smoke today. Government surveys show that about 25 percent of men and 20 percent of women smoke regularly, but smoking rates among younger women remain relatively high. Experts say women's gains in cancer deaths will take time to catch up with men's. And smoking rates for both sexes remain well above the goal of 12 percent or lower that public-health officials have set for adults for the end of this decade.

"The bottom line is that sustained progress in tobacco control is essential if we are to continue to make progress against cancer," said Dr. Michael Thun, co-author of the study and vice president for epidemiology and surveillance research for the cancer society.

He and co-author Amedin Jemal used two approaches to estimate the impact of reductions in smoking on cancer-death rates and the number of cancer deaths.

First, the researchers projected the increase in the rates of lung-cancer deaths in men and women that would have occurred had they continued to rise at historic rates. The scientists concluded that without the decline in smoking, there would be no decrease in death rates today, no matter what other advances in detection and treatment took place.

In their more conservative approach, the researchers simply applied the 1991 lung-cancer death rate in men to the U.S. male population in each year between 1991 and 2003. From this, they estimated that about 146,000 lung-cancer deaths were prevented or delayed by the drop in cancer rates, with reductions in smoking accounting for at least 40 percent of that figure.