Emerging Categories of Disease in Advanced Prostate Cancer and Their Therapeutic Implications

The treatment of advanced prostate cancer has changed significantly in the last decade, as a result of the introduction of multiple new systemic therapies that have had a positive impact on treatment outcomes. The increasing number of therapies, along with new insights into the biological underpinnings of prostate cancer, have led to a growing appreciation for the heterogeneity of the disease and an awareness of emerging subcategories that have direct therapeutic implications for the practicing clinician. In the metastatic hormone-naive setting, the extent of metastatic disease visible on scans can serve as a useful measure to guide treatment decisions; the addition of docetaxel chemotherapy to hormonal therapy has significant benefit in patients whose scans show more extensive disease. In the castration-resistant setting, abiraterone and enzalutamide have both had a transformative impact; however, the emergence of resistance to these therapies often heralds a more aggressive phenotype. Emerging clinically relevant subcategories include disease that demonstrates treatment-emergent neuroendocrine differentiation, as well as tumors with somatic and/or germline alterations in the DNA repair pathway. Identification of these subtypes has direct clinical relevance with regard to the potential benefit of platinum-based chemotherapy, poly (ADP-ribose) polymerase inhibitors, and likely further therapies as new therapeutic targets are identified in these groups.