The number of cancer deaths dropped to 556,902 in 2003, down from 557,271 the year before, according to a recently completed review of U.S. death certificates by the National Center for Health Statistics.
"It's smoking, it's earlier diagnosis, and it's improvement in treatment," Dr. Michael Thun, director of epidemiological research for the American Cancer Society, told CBS Radio News. "The biggest amount of credit goes to reductions in smoking over the last 40 to 50 years."
It's the first annual decrease in total cancer deaths since 1930, when nationwide data began to be compiled, "so it's the first downturn in nearly 75 years," Thun said.
The decline is welcome news in the medical community, said Arthur Caplan, University of Pennsylvania bioethicist.
"The war on cancer" has not always gone well in the public's eyes, Caplan noted. Despite decades of scientific research and screening campaigns, radiation and chemotherapy cancer treatments remained harsh and total deaths continued to rise, he noted.
"It's no surprise this dip in numbers would be greeted with joy by 'the commanders,' if you will, in the war on cancer," Caplan said.
For more than a decade, health statisticians have charted annual drops of about 1 percent in the cancer death rate — the calculated number of deaths per 100,000 people. But the actual number of cancer deaths still rose each year because the growth in total population outpaced the falling death rates.
"Finally, the declining rates have surpassed the increasing size of the population," said Rebecca Siegel, a Cancer Society epidemiologist.
Experts are attributing the success to declines in smoking, and the earlier detection and more effective treatment of tumors. Death rates have fallen for lung, breast, prostate and colorectal cancer, according to American Cancer Society officials, who analyzed the federal death data.
Those are the four most common cancers, which together account for 51 percent of all U.S. cancer deaths.
The breast cancer death rate has been dropping about 2 percent annually since 1990, a decline attributed to earlier detection and better treatment. The colon and rectum cancer death rate, shrinking by 2 percent each year since 1984, is also attributed to better screening. The prostate cancer death rate has been declining 4 percent annually since 1994, though the reasons for that are still being studied.
The lung cancer death rate for men, dropping about 2 percent a year since 1991, is because of reductions in smoking. The lung cancer death rate for women, however, has held steady, a sign that reflects a lag in the epidemic among women, who took up smoking later.
The total number of cancer deaths among women actually rose by 409 from 2002 to 2003. Among men, deaths fell by 778, resulting in a net decrease of 369 total cancer deaths.
With such a small drop in deaths, it's possible they will rise again when 2004 data is tabulated, said Jack Mandel, chairman of epidemiology at Emory University's Rollins School of Public Health.
Cancer is diagnosed more often in older people than younger people, and the large and aging population of Baby Boomers may push cancer statistics a bit. Even so, that should be offset by treatment improvements and declines in smoking and cancer incidence.
"I still think we're going to see a decline," Mandel said.
"One would predict that the number would continue to decrease," Thun said. "It may be hard to continue this when the baby boomers hit the late 60s and 70s, but in the near future, we would expect this to continue."
Thun said individuals can help the downward trend continue.
"Probably the easiest thing to do is, when you see your doctor next time, ask if you're getting the recommended screening for breast cancer for a woman and for a man, colon cancer," he said. "That can save your life."