The U.S. cancer death rate fell again in 2006, a new analysis shows, continuing a slow downward trend that experts attribute to declines in smoking, earlier detection and better treatment.
About 560,000 people died of cancer that year, according to an American Cancer Society report released Wednesday. The new numbers show the death rate fell by less than 2 percent, but since that decline was better than the previous year, the cancer society applauded the progress.
Others said the change was not a big deal.
"The improvement was modest," said Dr. Michael Goodman, an Emory University researcher who specializes in cancer statistics.
Cancer is the nation's No. 2 killer, behind heart disease, and accounts for nearly a quarter of annual deaths. The cancer death rate has been falling since the early 1990s.
The new rate shows 181 cancer deaths per 100,000 people. That was down from about 184 in 2005.
It takes a rate decline of at least 2 percent to offset population growth and cause a drop in the actual number of cancer deaths. That happened in 2002 and 2003 for the first time since 1930. But it hasn't happened since.
The explanation for why the death rate has fallen depends on the type of cancer. For example, better screening has improved deaths from colon cancer. Treatment advances are more of a factor in leukemia death rates. And smoking cessation is the main reason behind improvements in male lung cancer deaths.
"What we call 'cancer' is really a great variety of different conditions," Goodman said.
Lung cancer accounted for nearly 30 percent of cancer deaths in 2006. Cancers of the colon and rectum accounted for 10 percent, breast cancer in females about 7 percent and prostate cancers in men about 5 percent.
The statistical report is based on the cancer society's analysis of federal data.
Separate numbers on specific cancer death rates for 2006 from the U.S. Centers for Disease Control and Prevention sheds more light on the picture. The CDC recently reported death rates fell for:
• Lung and trachea cancers, from 54 deaths per 100,000 in 2005 to 51.5 in 2006.
• Colorectal cancers, from 18 to 17 per 100,000.
• Breast cancer, from 27 to 23.5 per 100,000.
Overall, it's hard to know exactly what drives one year's decline in cancer deaths, because the answer is rooted in the past, said Ahmedin Jemal, the cancer society official who lead the research behind the new report.
"When you introduce a change in screening or prevention, it takes five years or 10 years" to see the impact on cancer death rates, Jemal said. Treatment advances can have a more immediate impact, he added.
Cancer society officials estimate that 650,000 deaths were avoided from 1990 to 2005 because of the decline in the death rate. They predict that 1,479,350 new cancer cases will be diagnosed in 2009, and that there will be 562,340 deaths.
The new report is being released Wednesday online, and will be published in the July/August print issue of a Cancer Society publication, CA: A Cancer Journal for Clinicians.