Clinical phenotypes of castration-resistant prostate cancer

Castration-resistant prostate cancer (CRPC) is defined as prostate cancer that no longer responds to androgen deprivation therapy. At the genome level, CRPC is a heterogeneous disease that is marked by a range of genetic and epigenetic lesions. These lesions differ from patient to patient, but have common pathway-based themes. Clinically, a range of phenotypic presentations or subtypes of CRPC are observed that mirror this underlying heterogeneity as the disease progresses; each phenotype carries a different prognosis and different implications for treatment. In this review, we discuss the clinical subtypes of CRPC based on histology; the presence of metastatic disease and pattern of spread; patient-reported symptoms; and levels of biomarkers, such as serum bone turn- over biomarkers, prostate-specific antigen, circulating tumor cell enumeration, and neuroendocrine biomarkers. We then address the potential relationship between these clinical phenotypes (with their underlying molecular subtypes) and therapeutic decision- making and prognosis, as well as ongoing research strategies.