If you would have said that 40% of all protate cancers are discovered after death, we would have had no argument. For the most typical PC, patients diagnosed after 70 will not get any treatment, because they will die long before the disease becomes a threat.
However, breast and colon cancer are the prevelant cancers in the US, and the #1 & #2 cancer killers, respectively. The statement that 40% of all cancers are discovered post mortem doen not hold up.
And, by the way, these are NCI stats, are they not?