Prostate cancer is one of the most common cancers diagnosed in men worldwide and can be detected with elevated prostate-specific antigen (PSA) levels in the blood.
Prostate diagnosis at stage IV
However, an elevated PSA level can also be caused by other conditions; thus, PSA usage in population-wide screening programmes has long been debated. In the US, prostate cancer screening guidelines changed in 2008 in favour of decreased use of PSA in the general population, and again in 2011 against screening in all ages. These guideline changes significantly affected the epidemiology of prostate cancer in the US, resulting in a higher proportion of incident cases diagnosed at stage IV in the US.
GlobalData epidemiologists used incidence data obtained from the Surveillance, Epidemiology, and End Results (SEER) programme from 2008–2015 and estimated a decrease in the incident cases of prostate cancer, from around 220,000 cases in 2008 to around 165,000–170,000 cases in 2019.
When examining the incident cases by stage, GlobalData observed that the proportion of stage IV cases increased from around 6% in 2008 to 11% in 2015 — an 83% increase. We also observed that changes in stage at diagnosis have slowed in recent years. It is likely that the impact of screening changes in 2008 and 2011 has stabilised.
When looking at the data from the perspective of the number of cases, though, we see a 27% increase in stage IV, but there are large decreases in incident cases in other stages.
The graph below compares incident cases by stages at diagnosis in 2008 and 2019; 2019 values were estimated by holding rates in 2015 constant. The changes in national screening programmes in 2008 and 2011 aimed to decrease unnecessary medical treatment in those who would not benefit from cancer diagnosis since prostate cancer patients often live a long life and die of other causes.
However, the increase in stage IV cases is concerning as these cases are the most severe, have metastasized to other locations in the body, and have the worst survival. The recommendation against PSA screening in men of all ages was supported by findings from a clinical trial in 2009 that there were no differences in prostate cancer mortality between screened and unscreened men. It would be important to study outcomes in prostate cancer epidemiology after the screening guideline changes in 2011 to confirm whether the recommendation to not screen is still valid.
Prostate cancer incident cases by stage at diagnosis, 2008 and 2019
GlobalData (2019). EpiCast Report: Prostate Cancer – Epidemiology Forecast to 2028, to be published