Although I am sure Eric is correct that some doctors guess at the statistic they quote, Most (if not all) NCI designated Cancer Centers participate in the NCI's SEER(Surveillance,Epidemiology, and End Results)and SRP (Surveillance Research Program)programs along with maintaining significant databases of their own.

The NCI states that the SEER Program is the nation�s authoritative source of cancer incidence and survival data
from population-based cancer registries covering approximately 26% of the U.S. population

The number of data elements collected in SEER is more comprehensive than for any other national cancer surveillance system. SEER includes data on patient demographics, primary tumor site, tumor morphology and stage at diagnosis, first course of treatment, and follow-up for vital status. A repository of tissue specimens and a collection of biomarker information from laboratory health records.