CHICAGO – The United States has passed an important milestone in the fight against cancer, researchers reported Tuesday: For the first time, the recorded rate of new cancer cases has fallen for both men and women.

At the same time, a 15-year decline in cancer death rates has accelerated, meaning people in whom the disease has been diagnosed are living longer.

The report, published online Tuesday in the Journal of the National Cancer Institute, found the leading cancer scourges – including lung cancer, colon cancer and breast cancer – are on the wane, prompting experts to conclude that aggressive cancer-prevention and treatment efforts are paying off against the nation’s No. 2 killer.

“The drop in incidence seen in this year’s annual report is something we’ve been waiting to see for a long time,” said Dr. Otis Brawley, chief medical officer of the American Cancer Society.

While heralding the development, Brawley and other cancer experts sounded notes of caution. Fewer men and women are being screened for prostate and breast cancer, they noted, which can mean fewer tumors get identified. And as the population ages and the economy worsens, access to screening and medical treatments may decrease, eroding the gains.

The downward trend in new cancer diagnoses spans several years and was teased out through careful statistical analysis by researchers from the American Cancer Society, the National Cancer Institute, the U.S. Centers for Disease Control and Prevention, and the North American Association of Central Cancer Registries.

They found that cancer incidence – the rate at which new illnesses are diagnosed – dropped 0.8 percent annually between 1999 and 2006, a small but statistically significant reduction. The declines held for whites, blacks, Asian/Pacific Islanders and Hispanics.

Cancer death rates have been falling since 1993, but the report found that the rate of decline accelerated between 2002 and 2005, approaching nearly 2 percent a year. Experts credit more effective therapies and improved detection.

The positive trends don’t apply to all types of cancer. New cases are up for myeloma, non-Hodgkin lymphoma, melanoma, and cancers of the liver, kidney and esophagus. Death rates have risen for esophageal cancer in men, pancreatic cancer in women, and liver cancer for men and women.