Chapter 9 - Case Report #9—Biomarkers of Prostate Cancer

Abstract

Aside from their screening, diagnostic, and prognostic utilities, biomarkers are also considered predictive of treatment response. The prostate specific antigen (PSA) is the most widely used biomarker for prostate cancer screening and treatment follow-up, but it does have limitations, and so the development of more sensitive and more specific biomarkers become necessary. The first category is the PSA kinetics such as: PSA doubling time, which was very useful for our patient for treatment purpose; PSA velocity; PSA density; and age-specific PSA. Unfortunately, scientific evidence to date concerning those derivatives is not very optimistic. Then we have the PSA isoforms that includes: free PSA (fPSA), from which we can calculate the %fPSA; proPSA; intact PSA (iPSA); and benign PSA (bPSA). The prostate health index (PHI) is simply the following mathematical formula: ([−2]proPSA/fPSA)×√PSA. It combines all three evidence-based PSA biomarkers into a single score. Men with higher levels [−2]proPSA and PSA with lower levels of fPSA are more likely to have prostate cancer. The 4Kscore (4KS) is another biomarker that helps discriminate between indolent and aggressive prostate cancer. A prostate cancer antigen 3 PCA3 score below 25 is associated with a decrease in the likelihood of prostate cancer. C-reactive protein (CRP) is an acute-phase protein that has been associated with a poor prognosis of survival, as in our patient. Then we have the biomarkers for the follow-up response to treatment. For our patient, all the following were found useful: circulating tumor cells (CTC); neutrophil-to-lymphocyte ratio (NLR); circulating testosterone levels and androgen receptor splice variant 7 (AR-V7).