The number of deaths declined by only a sliver -- just 369 out of more than half a million between 2002 and 2003, the latest years for which data are available.

But the American Cancer Society, which conducted the analysis, believes the downward trend is solid, and the group is projecting a substantially larger decrease this year.

'A Remarkable Turn'

The results "mark a remarkable turn in our decades-long fight to eliminate cancer as a major health threat," said the society's chief executive officer John R. Seffrin. "For the first time, the advances we have made in prevention, early detection and treatment are outpacing even the population factors that ... obscured that success."

The number of cancer deaths in women actually increased by 409 in 2003, but that growth was offset by a decline of 778 in men, for a net decrease of 369 cases, according to data from the National Center for Health Statistics in Hyattsville, Md..

"That may seem like a small number, but it represents an important milestone," said Dr. Michael Thun, scientific director of the cancer society.

The society estimates that deaths in 2006 will total about 565,000, down from an estimated 570,280 in 2005.

Substantial Economic Benefits

A continued decline could have substantial economic benefits. In 2005, according to the National Institutes of Health, direct medical costs of cancer care totaled $74 billion, while lost productivity and other effects added an additional $136 billion.

The decline is "not surprising, but it is very gratifying," said Dr. Michael A. Friedman, president of City of Hope National Medical Center in Duarte, Calif. "It has taken quite a long time for us to reach this point."

The disease still causes one in every four US deaths, making it second only to heart disease. But the rate of cancer deaths has been declining steadily by about 1 percent per year since 1991 as individual survival has improved.

When the government first began keeping records 75 years ago, the US population was only 123 million and cancer accounted for 114,186 deaths every year.

A cancer diagnosis was nearly equivalent to a death sentence, the only treatments being rudimentary surgery and blasts of radiation, which was first used at the turn of the century.

The first chemotherapy drugs, which were derived from the poisons used in chemical warfare, were developed during World War II, but did not see much use for another decade. The first recorded cure of a metastatic cancer with drugs only occurred in 1956, when methotrexate was used to treat a rare tumor called choriocarcinoma.

Reduction in Tobacco Use

The first major step toward prevention was the Surgeon General's report on smoking in 1964, which delineated the hazards of tobacco, but it took two decades for that message to begin having a profound effect on smoking rates.

By the 1970s, half of those diagnosed with cancer survived for five years. For those diagnosed during the last half of the 1990s, the rate has grown to 65 percent. Today, the National Cancer Institute estimates that there are 10.1 million living Americans who have had cancer. Over their entire lifetimes, men have just under a one in two risk of developing cancer, while women have a risk of just over one in three.

The biggest contributor to the falling death rate is the reduction in tobacco use over the last 30 years, according to Thun. Tobacco use accounts for 30 percent of all cancer deaths, including lung cancer and 14 other types. Lung cancer is the most common cause of cancer deaths in both men and women and will account for an estimated 162,460 deaths this year.

The incidence of lung cancer in men has fallen by about 24 percent since 1985. Among women, who did not begin smoking heavily until decades after men did, the incidence has leveled off since 1998 after a long period of growth.

Healthier Food

Other important contributors to the decline are breast, prostate and colorectal cancers.

Breast cancer deaths have declined about 2.3 percent per year since 1990 to an estimated 40,970 deaths in women this year and 460 in men. The declines are attributed to improvements in treatment and early diagnosis, which allows tumors to be detected while they are still curable.

Prostate cancer incidence has been rising and falling irregularly over the past decade as a result of changes in testing, but prostate cancer deaths have been falling steadily, to an estimated 20,360 this year. The death rates have been falling in both whites and blacks, but black men are still twice as likely to die from the disease.

Colorectal cancer deaths have been declining slowly, to an estimated 55,170 this year, as screening has increased -- although fewer than 50 percent of those for whom screening is recommended now receive it. Screening allows the identification of benign polyps, which can be removed before they turn cancerous.

Treatments for colorectal cancer have also been improving, and the incidence is falling, "but we don't know why for sure," Thun said.

"In general, people are eating more healthy food and going in for checkups more often," Friedman said.