Management of Nonmetastatic Castration-Resistant Prostate Cancer: Recent Advances and Future Direction.

OPINION STATEMENT: Nonmetastatic castration-resistant prostate cancer (nmCRPC) comprises a relatively narrow niche of advanced prostate cancer, but the treatment landscape for men with nmCRPC has drastically changed over the past year. Prior to the SPARTAN and PROSPER trials, men with nmCRPC were commonly treated with first-generation androgen receptor antagonists, such as bicalutamide or flutamide, or with estrogens or ketoconazole, none of which were associated with any proven survival benefit. The SPARTAN trial evaluated apalutamide versus placebo for men with nmCRPC and found that apalutamide significantly improved metastasis-free survival (MFS), the primary endpoint of this trial. Similarly, the PROSPER trial showed that enzalutamide significantly improved MFS compared with placebo for men with nmCRPC. In both trials, the data for overall survival was immature at the time of analysis. The SPARTAN and PROSPER trials led to the approval of apalutamide and enzalutamide, respectively, for men with nmCRPC. More recently, the phase 3 trial ARAMIS showed that darolutamide, a novel androgen receptor antagonist, also improves MFS compared with placebo for men with nmCRPC, and this trial is expected to garner regulatory approval for darolutamide in the nmCRPC setting. Novel imaging modalities are becoming more prevalent for the diagnostic evaluation of men with prostate cancer and are more sensitive than conventional bone or CT scans for detection of oligometastatic disease that previously was undetected. These modalities are likely to reduce the incidence and prevalence of nmCRPC in the near future. Ultimately, the treatment options for men with nmCRPC have significantly improved over the past 2 years.

DNA Damage Repair (DDR) Mutations and the Utility of High-Risk Genetics Clinics in Metastatic Castration-Refractory Prostate Cancer (mCRPC).

Germline pathogenic variants (PVs) in DNA-repair genes have garnered increasing attention in metastatic prostate cancer, and more patients are having somatic and germline DNA testing performed. Interpretation of germline DNA testing is a novel challenge for many clinicians, and the results of germline DNA-repair gene testing have significant implications for men with advanced prostate cancer and their children and siblings. Here, we report the case of a man with metastatic castration-refractory prostate cancer and a pathogenic, germline BRCA2 variant. We discuss the significance of his referral to a high-risk genetics clinic and the unique targeted therapy that he responded to.

RON kinase: A target for treatment of cancer-induced bone destruction and osteoporosis.

Bone destruction occurs in aging and numerous diseases, including osteoporosis and cancer. Many cancer patients have bone osteolysis that is refractory to state-of-the-art treatments, which block osteoclast activity with bisphosphonates or by inhibiting the receptor activator of nuclear factor κB ligand (RANKL) pathway. We previously showed that macrophage-stimulating protein (MSP) signaling, which is elevated in about 40% of breast cancers, promotes osteolytic bone metastasis by activation of the MSP signaling pathway in tumor cells or in the bone microenvironment. We show that MSP signals through its receptor, RON tyrosine kinase, expressed on host cells, to activate osteoclasts directly by a previously undescribed pathway that is complementary to RANKL signaling and converges on proto-oncogene, non-receptor tyrosine kinase SRC (SRC). Genetic or pharmacologic inhibition of RON kinase blocked cancer-mediated bone destruction and osteoporosis in several mouse models. Furthermore, the RON kinase inhibitor BMS-777607/ASLAN002 altered markers of bone turnover in a first-in-human clinical cancer study, indicating the inhibitor's potential for normalizing bone loss in patients. These findings uncover a new therapeutic target for pathogenic bone loss and provide a rationale for treatment of bone destruction in various diseases with RON inhibitors.