Cancer in decline?

The incidence of new cancer cases has been falling in recent years in the United States, the first time such an extended decline has been documented, researchers reported Tuesday.

Cancer diagnosis rates decreased by an average of 0.8 percent each year from 1999 to 2005, the last year for which data are available, according to an annual report by the National Cancer Institute, the American Cancer Society and other scientific organizations.-- NYT

It is likely a real effect and not e.g., an artifact of less screening. If you consider that the population has been greying over this period, this seems rather significant.

PS: from various census.gov sources, the median age of the US population in 2000 was 35.3 and in 2006 was 36.2.