MONDAY, March 7, 2005 (HealthDay News) -- The gender gap in lung cancer rates in the United States is narrowing as rates among men decline while rates among women remain steady, according to a study in the March issue of Chest.
"Traditionally, lung cancer has been viewed as a disease of older male smokers, but that is not necessarily the case," study author Dr. Gregory P. Kalemkerian, of the University of Michigan Medical Center, said in a prepared statement.
"This data supports the fact that lung cancer is becoming a bigger problem in women every year. If these current trends continue, in 10 to 15 years, the incidence of lung cancer will be identical for women and men," he said.
Researchers from the University of Michigan Medical Center and Wayne State University analyzed data on nearly 82,000 female and 147,000 male lung cancer patients registered in a national database between 1974 and 1999.
Lung cancer incidence among men peaked in 1984, when 72.5 of every 100,000 men had the disease, then dropped to 47 men per 100,000 by 1991. However, the incidence of lung cancer among women peaked in 1991 at 33.1 per 100,000, but then remained steady at 30.2 to 32.3 per 100,000 from 1992 to 1999.
This means that the ratio of male-to-female lung cancer patients has changed from about 3.5-to-1 in 1975, to just 1.5-to-1 by 1999, the researchers report. The mean age of lung cancer diagnosis for both women and men was 66 years, with women accounting for close to 41 percent of lung cancer patients under age 50 and more than 35 percent of patients over age 50.
"The fact that women appear to be overrepresented among patients under the age of 50 is a reflection of increased smoking prevalence among women, especially early in the study period," Kalemkerian said.
"There is still controversy as to whether or not women are more susceptible to tobacco carcinogens, but our findings suggest that women and men are affected differently by their tobacco use. For example, nearly half the women (44.7 percent) developed adenocarcinoma, while the men were most likely to develop squamous cell carcinoma (36.3 percent)," he said.
This study also found that female lung cancer patients had higher survival rates than men at every stage of the disease. From 1975 to 1987, the five-year survival rate for women was about 12 percent greater than for men. From 1988 to 1999, the five-year survival rate for women was 6.5 percent higher than for men.
Male lung cancer patients frequently have other health problems, such as heart disease or severe emphysema, and that may explain why they have a lower survival rate, the researchers said.
The American Cancer Society's latest projections, released in January, also found a diminished gender gap in lung cancer rates overall. From 1998 to 2001, lung cancer continued to decrease in men and, for the first time, also in women, they report.
The American Cancer Society has more about lung cancer.