For the first time since the government began compiling records, the rate of cancer has begun to decline, marking a tipping point in the fight against the second-leading cause of death among Americans.
Researchers already knew that the number of cancer deaths was declining as the result of better treatment, but the drop in incidence indicates that major progress also is being made in prevention.
“The drop in incidence … is something we have been waiting to see for a long time,” said Dr. Otis W. Brawley, chief medical officer of the American Cancer Society.
And “the continuing drop in mortality is evidence once again of real progress made against cancer, reflecting real gains in prevention, early detection and treatment.”
But the declines may be temporary, said Dr. Robert Figlin, of the City of Hope Comprehensive Cancer Center, in Duarte, Calif.
“Baby boomers are reaching the age at which they develop cancer … so we should not be surprised if it changes direction again,” he said.
Researchers also fear that the economic meltdown may trigger a new increase in incidence as fewer people feel comfortable paying for screening tests and increased stress leads some people to resume smoking.
Incidence rates for all cancers in men and women dropped by 0.8 percent per year from 1999 through 2005, with the rates for men dropping at about three times the rate for women.
The only ethnic groups for which rates did not decline were American Indians and Alaskan Natives.
The overall death rate declined by an average of 1.8 percent per year over the same period.
Currently, about 1.4 million Americans are diagnosed with cancer each year, and an estimated 560,000 die of it.
The decline in both incidence and death rates was due in large part to declines in five of the six most common cancers – lung, colorectal and prostate in men and breast and colorectal cancer in women.
The sixth most common form, lung cancer in women, leveled off.
Those cancers alone account for about half of both new cases and deaths.
“Lung cancer is the big one when it comes to cancer in the United States,” said Dr. John Glaspy, of the Jonsson Comprehensive Cancer Center at the University of California, Los Angeles.
The declines in lung cancer are due primarily to widespread reductions in smoking.
“It’s very tough for anybody not to conclude that social trends (against) smoking are having major effects on human life.”
The decline in breast cancer incidence is most likely due to the sharply reduced use of hormone replacement therapy beginning in 2002, as has been noted in several previous studies.
The drop in colon and rectal cancer, the report says, most likely stems from increases in screening, which leads to the identification and removal of polyps before they become cancerous.
It is not clear why the incidence of prostate cancer has declined, but it may be a result of a leveling-off in screening since 2002, the report’s authors said.
Overall, the incidence rates dropped for 10 of the top 15 cancers.
But not all the news is good.
For men, the incidence is rising for cancers of the liver, kidney and esophagus, as well as for melanoma, non-Hodgkin’s lymphoma and myeloma.
For women, the incidence is rising for cancers of the thyroid, pancreas and brain and nervous system, and for leukemia.
“This report gives us a better understanding of where we may need to redouble our efforts and try to find new ways of preventing … kidney, liver and other cancers that continue to show increases in both mortality and incidence,” said Dr. John Niederhuber, director of the National Cancer Institute.