Platinum-based chemotherapy is not standard of care for unselected or genetically selected metastatic castration-resistant prostate cancer (mCRPC) patients. A retrospective assessment of 71 patients was performed on platinum use in the Netherlands. Genetically unselected patients yielded low response rates. For a predefined subanalysis of all patients with comprehensive next-generation sequencing, 30 patients were grouped based on the presence of pathogenic aberrations in genes associated with DNA damage repair (DDR) or aggressive variant prostate cancer (AVPC). Fourteen patients (47%) were DDR deficient (DDRd), of which seven with inactivated BRCA2 (BRCA2mut). Six patients classified as AVPC. DDRd patients showed beneficial biochemical response to carboplatin, largely driven by all BRCA2mut patients having >50% prostate-specific antigen (PSA) decline and objective radiographic response. In the wild-type BRCA2 subgroup, 35% had a >50% PSA decline (P = .006) and 16% radiographic response (P < .001). Median overall survival was 21 months for BRCA2mut patients vs 7 months (P = .041) for those with functional BRCA2. AVPC patients demonstrated comparable responses to non-AVPC, including a similar overall survival, despite the poor prognosis for this subgroup. In the scope of the registration of poly-(ADP)-ribose polymerase inhibitors (PARPi) for mCRPC, we provide initial insights on cross-resistance between PARPi and platinum compounds. By combining the literature and our study, we identified 18 patients who received both agents. In this cohort, only BRCA2mut patients treated with
PURPOSE Although most patients with microsatellite instable (MSI) metastatic castration-resistant prostate cancer (mCRPC) respond to immune checkpoint blockade (ICB), only a small subset of patients with microsatellite stable (MSS) tumors have similar benefit. Biomarkers defining ICB-susceptible subsets of patients with MSS mCRPC are urgently needed. METHODS Using next-generation T-cell repertoire sequencing, we explored immune signatures in 54 patients with MSS and MSI mCRPC who were treated with or without ICB. We defined subset-specific immune metrics as well as T-cell clusters and correlated the signatures with treatment benefit. RESULTS Consistent overlaps between tumor and peripheral T-cell repertoires suggested that blood was an informative material to identify relevant T-cell signatures. We found considerably higher blood T-cell richness and diversity and more shared T-cell clusters with low generation probability (pGen) in MSI versus MSS mCRPC, potentially reflecting more complex T-cell responses because of a greater neoepitope load in the MSI subset. Interestingly, patients with MSS mCRPC with shared low pGen T-cell clusters showed significantly better outcomes with ICB, but not with other treatments, compared with patients without such clusters. Blood clearance of T-cell clusters on ICB treatment initiation seemed to be compatible with T-cell migration to the primary tumor or metastatic sites during the process of clonal replacement as described for other tumors receiving ICB. CONCLUSION The MSI mCRPC subset shows a distinct T-cell signature that can be detected in blood. This signature points to immune parameters that could help identify a subset of patients with MSS mCRPC who may have an increased likelihood of responding to ICB or to combination approaches including ICB.
The clinical utility of circulating tumor cells (CTC) as a non-invasive multipurpose biomarker is broadly recognized. The earliest methods for enriching CTCs from whole blood rely on antibody-based positive selection. The prognostic utility of CTC enumeration using positive selection with the FDA-approved CellSearchTM system has been demonstrated in numerous studies. The capture of cells with specific protein phenotypes does not fully represent cancer heterogeneity and therefore does not realize the prognostic potential of CTC liquid biopsies. To avoid this selection bias, CTC enrichment based on size and deformability may provide better fidelity, i.e., facilitate the characterization of CTCs with any phenotype. In this study, the recently FDA-approved Parsortix® technology was used to enrich CTCs from prostate cancer (PCa) patients for transcriptome analysis using HyCEADTM technology. A tailored PCa gene panel allowed us to stratify metastatic castration-resistant prostate cancer (mCRPC) patients with clinical outcomes. In addition, our findings suggest that targeted CTC transcriptome profiling may be predictive of therapy response.
Background
Molecular tumour boards (MTB) optimally match oncological therapies to patients with genetic aberrations. Prostate cancer (PCa) is underrepresented in these MTB discussions. This study describes the impact of routine genetic profiling and MTB referral on the outcome of PCa patients in a tertiary referral centre.
Methods
All PCa patients that received next-generation sequencing results and/or were discussed at an MTB between Jan 1, 2017 and Jan 1, 2020 were included. Genetically matched therapies (GMT) in clinical trials or compassionate use were linked to actionable alterations. Response to these agents was retrospectively evaluated.
Results
Out of the 277 genetically profiled PCa patients, 215 (78%) were discussed in at least one MTB meeting. A GMT was recommended to 102 patients (47%), of which 63 patients (62%) initiated the GMT. The most recommended therapies were PARP inhibitors (n = 74), programmed death-(ligand) 1 inhibitors (n = 21) and tyrosine kinase inhibitors (n = 19). Once started, 41.3% had a PFS of ≥6 months, 43.5% a PSA decline ≥50% and 38.5% an objective radiographic response.
Conclusion
Recommendation for a GMT is achieved in almost half of the patients with advanced prostate cancer, with GMT initiation leading to durable responses in over 40% of patients. These data justify routine referral of selected PCa patients to MTB’s.
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