Castration-resistant prostate cancer with bone metastases: toward the best therapeutic choice

The treatment landscape for metastatic castration-resistant prostate cancer has evolved extremely in recent years and several drug classes are now available. Nonetheless, the lack of validated predictive biomarkers makes therapeutic choice and the best sequential approach difficult. The location of the metastatic site could be a valid criterion for choosing among the treatment options available. Although bone remains the most frequent metastatic site and a possible target for many drugs, recent data suggest a profound shift in the disease spectrum with visceral metastases increasing incidence. This review describes the presently available and ongoing therapies for patients with CRPC and bone metastases, focusing on the role of bone metastases as a possible driver for selecting therapies in these patients.

Neoadjuvant treatment with androgen receptor signaling inhibitors prior to radical prostatectomy: a systematic review

CONTEXT

There is an urgent need to develop novel treatment strategies in patients with unfavorable intermediate- and high-risk localized prostate cancer (PCa) to optimize the outcome of these patients. Androgen receptor signaling inhibitors (ARSI) have demonstrated a survival benefit in metastatic hormonesensitive and castration-resistant PCa. A similar benefit might be expected in the localized setting.

OBJECTIVE

To perform a systematic review about the role of neoadjuvant ARSI in unfavorable intermediate and high-risk localized PCa.

EVIDENCE ACQUISITION

We performed a systematic review of the following databases: MEDLINE (PubMed), EMBASE, Cochrane Library and Web of Science. Publications of ASCO were consulted to identify meeting abstract with early results of ongoing trials. This systematic review was performed and reported in accordance with the PRISMA guidelines.

EVIDENCE SYNTHESIS

Pathological complete response (pCR) following neoadjuvant ARSI treatment was observed in 4%-13% of the patients. Minimal residual disease response ranged from 36% to 73.9% when defined as residual cancer burden < 0.25 cm³ at final pathology and from 8% to 20% when defined as the diameter of the remaining tumor < 5 mm. Despite intense neoadjuvant ARSI treatment, residual pT3 disease was observed in 48%-76% of the patients. In contrast, positive surgical margins (PSM) were present in only 5%-22%. Only one trial reported BCR following neoadjuvant ARSI therapy (44% BCR at a median follow-up of 4 years).

CONCLUSION

Despite intense neoadjuvant ARSI therapy, pCR is rarely attained and high proportions of pT3 disease are still observed at final pathology. In contrast, promising results are obtained in terms of PSMs. Long-term survival outcomes are eagerly awaited.

Improved Androgen Receptor Splice Variant 7 Detection Using a Highly Sensitive Assay to Predict Resistance to Abiraterone or Enzalutamide in Metastatic Prostate Cancer Patients

BACKGROUND

In metastatic castration-resistant prostate cancer (mCRPC), androgen receptor splice variant 7 (AR-V7) expression is associated with a low response to androgen receptor signaling (ARS) inhibitors such as abiraterone or enzalutamide.

OBJECTIVE

To perform a highly sensitive assay for detecting AR-V7 (hsAR-V7) in circulating tumor cells (CTCs) and evaluate its ability to predict response to ARS inhibitors.

DESIGN, SETTING, AND PARTICIPANTS

From 41 mCRPC patients, CTCs were prospectively enriched using AdnaTest platform and analyzed for AR-V7 with and without the highly sensitive assay.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The first objective of the study was to compare AR-V7 detection rates with and without the highly sensitive assay. Next, we investigated how AR-V7 (detected without the highly sensitive assay) and hsAR-V7 status influenced prostate-specific antigen (PSA) response and long-term clinical outcomes (PSA progression-free survival [PFS] and radiological PFS) after ARS-inhibitor treatment. Finally, discriminatory abilities of the assays were assessed by C-index to compare their impact on long-term clinical outcomes.

RESULTS AND LIMITATIONS

AR-V7 detection rates increased from 22% to 56% when the highly sensitive assay was used. The discriminatory abilities of hsAR-V7 for PSA PFS (C-index, 0.74; 95% confidence interval [CI], 0.60-0.88) and radiological PFS (0.70; 95% CI, 0.55-0.85) were higher than those of AR-V7 detected without the highly sensitive assay (0.60, 0.51-0.72, and 0.56, 0.44-0.67, respectively). After ARS-inhibitor treatment, PSA response was lower in hsAR-V7⁺ (53%) than in hsAR-V7^- (93%) patients (p = 0.016). AR-V7⁺ patients had shorter median PSA PFS (3.0 vs 10.6 mo, p = 0.032) and nonsignificantly shorter median radiological PFS (6.0 vs 14.8 mo, p = 0.24) compared with AR-V7^- patients. The hsAR-V7⁺ status was associated with shorter median PSA PFS (3.0 mo vs not reached, p = 0.0001) and radiological PFS (median, 6.0 mo vs not reached, p = 0.0026).

CONCLUSIONS

The hsAR-V7 assay achieved the highest AR-V7 detection rates among those reported in mCRPC. Discriminatory abilities for long-term clinical outcomes were better with hsAR-V7 assay.

PATIENT SUMMARY

We prospectively analyzed circulating tumor cells from men with metastatic castration-resistant prostate cancer for androgen receptor splice variant 7 (AR-V7) status using a highly sensitive assay. It yielded higher AR-V7 detection rates and predicted resistance to androgen receptor signaling inhibitors with better discriminatory abilities for long-term clinical outcomes.