ATLANTA – The tide has turned in the nation’s battle against cancer.

Cancer deaths in the United States dropped for the second year in a row, health officials reported Wednesday, confirming that the trend is real and becoming more pronounced, too.

The news was cause for celebration among doctors and politicians.

“It’s very exciting,” said Dr. Felice Schnoll-Sussman, a cancer physician at New York-Presbyterian Hospital/Weill Cornell Medical Center. “When we saw the first decline, the number wasn’t that enormous. But once you start to see a trend like this, it obviously makes you feel like “We must be doing something right!”‘

Cancer deaths in the U.S. in 2004 fell to 553,888 – a drop-off of 3,014 deaths, or 0.5 percent, from the year before, according to a review of U.S. death certificates conducted by the National Center for Health Statistics and released by the American Cancer Society.

Cancer deaths also fell in 2003, the first drop seen since 1930. But that decline was so small – just 369 deaths – that experts were hesitant at the time to say whether it was a triumph of medicine or just a statistical fluke.

Now, it appears “it’s not only continuing; the decrease in the second year is much larger,” said Ahmedin Jemal, an American Cancer Society researcher.

Experts are attributing the success to declines in smoking and to earlier detection and more effective treatment of tumors. Those have caused a fall in the death rates for breast, prostate and colorectal cancer – three of the most common cancers. The lung cancer death rate in men has also been falling, but the female rate has reached a plateau.

On a visit to the National Institutes of Health in Bethesda, Md., President Bush hailed the drop in cancer deaths as a signal that medicine – especially federally funded research – is making strides against a disease that still kills nearly 1,500 Americans a day.

The Cancer Society did not release cancer death data broken down by state, race or ethnicity. Those statistics are to be completed later this year.

The largest drop in deaths among the major cancers was in colorectal cancer. Colorectal cancer deaths dropped by 1,110 in men and by 1,094 in women. Experts said much of the credit goes to screening exams such as colonoscopies that detect polyps and allow doctors to remove them before they turn cancerous.

Some doctors say at least part of the success can be attributed to “the Katie Couric effect.” A 2003 study found colonoscopy rates jumped more than 20 percent in the months after the “Today” show host underwent a colonoscopy on national television in 2000, after her husband died of colon cancer.

Increased insurance coverage of colonoscopies has also led to more diagnostic screenings, said Dr. A. Mark Fendrick, the University of Michigan physician who led that study.

For more than a decade, health statisticians charted annual drops of about 1 percent in the cancer death rate – that is, the number of deaths per 100,000 people. But the actual number of cancer deaths still rose each year because of the growing elderly population and the size of the population overall.

Then, in 2003 and 2004, the cancer death rate declined by about 2 percent each year, more than offsetting the effects of aging and population growth.

The American Cancer Society said it believes cancer deaths will continue to drop.

Others shared that optimism.

“We’re starting to see some real dividends” from screening, prevention and treatment efforts, said Dr. Otis Brawley, an Emory University researcher specializing in cancer epidemiology.