Changes in net survival rates happen slowly and in small amounts. Comparing the periods of 2002 to 2008 and 2009 to 2015, nine sites had a detectable change in their five-year net survival rates.
We cannot say why the changes happened without a closer investigation. Better screening can improve net survival but probably did not in these cases. Out of the nine types with a detectable change, only stomach cancer had a meaningful change in the proportion of cases caught early. It was 23.1 percent of all invasive stomach cancers diagnosed from 2002 to 2008 and 25.6 percent of 2009 to 2015 diagnoses.
Prostate cancer had the only detectable decrease in five-year net survival. However, the decrease was small, from 98.1 percent during the 2002 to 2008 period to 96.0 percent for 2009 to 2015. A change in a screening recommendation in 2012 was possibly a part of this shift. The United States Preventive Services Task Force (USPSTF) recommended against routine screening for prostate cancer in men without symptoms. A decrease in screening could have delayed the diagnosis of prostate cancers until they reached a late stage and caused noticeable symptoms. For calculating the 2002 to 2008 net survival rate, 80.5 percent of the cases used were diagnosed at a localized stage. For the 2009 to 2015 rate, 77.2 percent were localized. Again, this was a small change.
Pancreatic cancer is mostly diagnosed at a late stage (see the Stage section). But the five-year net survival rate for pancreatic cancer increased a large amount for patients who caught it early.
Neither the USPSTF or the American Cancer Society (ACS) recommend patients without symptoms screen for pancreatic cancer. People should see a physician if they notice any of these symptoms (ACS 2019c):
Usually, these symptoms are caused by conditions besides pancreatic cancer.