By Chris Adams

Cancer deaths in the U.S. have been falling for several years, mainly because of a reduction in smoking and the resultant decrease in lung cancer.

Detailing those numbers – and how researchers arrive at them – was the focus of  a talk by a Centers for Disease Control and Prevention expert with National Press Foundation fellows.

Jane Henley, an epidemiologist for the CDC’s Division of Cancer Prevention and Control, is an author of the “Annual Report to the Nation on the Status of Cancer,” a collaboration of several organizations for cancer incidence surveillance.

The U.S. has one of the most robust surveillance systems in the world, collecting data from cancer registries and mortality systems from all states. It covers 100% of the population and compiles demographic information (sex, race, address), clinical data (date of diagnosis, date of treatment) and diagnostic information (cancer site and stage).

The information is available for journalists, researchers and the public at large at the CDC’s data visualization site. It’s broken down into states, counties and even congressional districts. It allows journalists to get specific fast: A quick query on leukemia rates in Alabama’s congressional districts finds an estimated 566 new cases of leukemia in District 5 between 2012 and 2016. Of those, an estimated 296 people died.

Henley detailed how the CDC presents its statistics, including the difference between incidence and incidence rate – the number of cases (incidence) may be going up even if the percentage of people getting the cancer (incidence rate) may be dropping.