Circulating tumor cells versus objective response assessment predicting survival in metastatic castration-resistant prostate cancer patients treated with docetaxel chemotherapy

Circulating Biomarkers Predictive of Treatment Response in Patients with Hormone-sensitive or Castration-resistant Metastatic Prostate Cancer: A Systematic Review

BACKGROUND AND OBJECTIVE

Metastatic prostate cancer (mPCa) harbors genomic alterations that may predict targeted therapy efficacy. These alterations can be identified not only in tissue but also directly in biologic fluids (ie, liquid biopsies), mainly blood. Liquid biopsies may represent a safer and less invasive alternative for monitoring patients treated for mPCa. Current research focuses on the description and validation of novel predictive biomarkers to improve precision medicine in mPCa. Our aim was to systematically review the current evidence on liquid biopsy biomarkers for predicting treatment response in mPCa.

METHODS

We systematically searched Medline, Web of Science, and evidence-based websites for publications on circulating biomarkers in mPCa between March 2013 and February 2024 for review. Endpoints were: prediction of overall survival, biochemical or radiographic progression-free survival after treatment (chemotherapy, androgen deprivation therapy, androgen receptor pathway inhibitors [ARPIs], immunotherapy, or PARP inhibitors [PARPIs]). For each biomarker, the level of evidence (LOE) for clinical validity was attributed: LOE IA and IB, high level of evidence; LOE IIB and IIC, intermediate level; and LOE IIIC and LOE IV-VD, weak level.

KEY FINDINGS AND LIMITATIONS

The predictive value of each biomarker for the response to several therapies was evaluated in both metastatic hormone-sensitive (mHSPC) and castration-resistant prostate cancer (mCRPC). In patients with mCRPC, BRCA1/2 or ATM mutations predicted response to ARPIs (LOE IB) and PARPIs (LOE IIB), while AR-V7 transcripts or AR-V7 protein levels in circulating tumor cells (CTCs) predicted response to ARPIs and taxanes (LOE IB). CTC quantification predicted response to cabazitaxel, abiraterone, and radium-223 (LOE IIB), while TP53 alterations predicted response to 177Lu prostate-specific membrane antigen radioligand treatment (LOE IIB). AR copy number in circulating tumor DNA before the first treatment line and before subsequent lines predicted response to docetaxel, cabazitaxel, and ARPIs (LOE IIB). In mHSPC, DNA damage in lymphocytes was predictive of the response to radium-223 (LOE IIB).

CONCLUSIONS AND CLINICAL IMPLICATIONS

BRCA1/2, ATM, and AR alterations detected in liquid biopsies may help clinicians in management of patients with mPCa. The other circulating biomarkers did not reach the LOE required for routine clinical use and should be validated in prospective independent studies.

PATIENT SUMMARY

We reviewed studies assessing the value of biomarkers in blood or urine for management of metastatic prostate cancer. The evidence indicates that some biomarkers could help in selecting patients eligible for specific treatments.

Bone flare after initiation of novel hormonal therapy in patients with metastatic hormone-sensitive prostate cancer: A case report

BACKGROUND

The 2020 European Association of Urology prostate cancer guidelines recommend androgen deprivation therapy (ADT) in combination with apalutamide and enzalutamide, a new generation of androgen receptor antagonists, as first-line therapy. A decrease in prostate-specific antigen (PSA) levels may occur in the early stages of novel hormonal therapy; however, radionuclide bone imaging may suggest disease progression. During follow-up, PSA, radionuclide bone imaging, and prostate-specific membrane antigen (PSMA) positron emission tomography – computed tomography (PET-CT) are needed for systematic evaluation.

CASE SUMMARY

We admitted a 56-year-old male patient with metastatic hormone-sensitive prostate cancer. Initial radionuclide bone imaging, magnetic resonance imaging (MRI), and PSMA PET-CT showed prostate cancer with multiple bone metastases. Ultrasound-guided needle biopsy of the prostate revealed a poorly differentiated adenocarcinoma of the prostate with a Gleason score: 5+4 = 9. The final diagnosis was a prostate adenocarcinoma (T₄N₁M₁). ADT with novel hormonal therapy (goseraline sustained-release implant 3.6 mg monthly and apalutamide 240 mg daily) was commenced. Three months later, radionuclide bone imaging and MRI revealed advanced bone metastasis. However, PSMA PET-CT examination showed a significant reduction in PSMA aggregation on the bone, indicating improved bone metastases. Considering that progressive decrease in the presenting lumbar pain, treatment strategies were considered to be effective.

CONCLUSION

ADT using novel hormonal therapy is effective for treating patients with prostate adenocarcinoma. Careful evaluation must precede treatment plan changes.

Evaluation of [68Ga]Ga-PSMA PET/CT for therapy response assessment of [177Lu]Lu-PSMA radioligand therapy in metastasized castration refractory prostate cancer and correlation with survival

PURPOSE

The aim of this retrospective study was to evaluate the use of [68Ga]Ga-PSMA PET/CT in therapy response assessment (TRA) of mCRPC patients treated with [177Lu]Lu-PSMA-617 and its correlation with overall survival (OS).

METHODS

Thirty-nine patients were included in the study. Patient-/lesion-based early and late response assessment (ERA/LRA) was defined as PET2 (after two therapy cycles) vs. PET1 (before the first cycle) (n = 29) and end of treatment PET vs. PET1 (n = 17), respectively. PET-based response (PET parameters; modified (m) PERCIST/EORTC), biochemical response (ΔPSA; category-based) and category-based clinical response (CRA) was tested for correlation/agreement. PET-based TRA was correlated with OS.

RESULTS

A significant correlation/agreement was shown between PET parameters and CRA as well as biochemical response in LRA of all lesions and between mPERCIST-based and category-based PSA response assessment in LRA (bone lesion-based, P = 0.045, κ = 0.184). At ERA, OS was significantly higher in CR/PR/SD compared to progressive disease applying mPERCIST/EORTC criteria (P = 0.0024).

CONCLUSION

In [177Lu]Lu-PSMA-617-treated mCRPC patients OS of the group of CR/PR/SD was significantly higher compared to the progressive disease group (mPERCIST/EORTC) in ERA. Therefore, [68Ga]Ga-PSMA PET might serve as a complementary diagnostic tool for TRA offering prognostic value regarding OS.

Clinical prognostic value of circulating tumor cells in the treatment of pancreatic cancer with gemcitabine chemotherapy

Pancreatic cancer (PC) is a highly malignant tumor type with a high early metastasis rate and no obvious symptoms. Gemcitabine is a first-line chemotherapeutic drug for PC. Since there is no distinct method to determine the efficacy of chemotherapy with gemcitabine in patients with PC, the purpose of the present study was to determine whether positivity for circulating tumor cells (CTCs) in patients with advanced PC is associated with response to gemcitabine chemotherapy and to explore whether CTCs may be used as a predictor of prognosis of patients with advanced PC undergoing chemotherapy. First, immunomagnetic microspheres (magnetic beads; MIL) were prepared to detect CTCs. The patients' clinical characteristics and survival data, as well as efficacy and adverse effects of chemotherapy, were prospectively obtained and their association with CTCs was analyzed. The results indicated that CTC-positive patients with advanced PC had a higher probability of developing resistance to gemcitabine chemotherapy than CTC-negative patients. Survival in the CTC-negative group was significantly higher than in the CTC-positive group (χ²=14.58, P<0.001). CTC-positive patients with advanced PC also had shorter progression-free survival (PFS) after chemotherapy with gemcitabine (P=0.01). In conclusion, CTC-positive patients with PC are more likely to develop gemcitabine resistance, have poor PFS and low incidence of thrombocytopenia. CTCs are expected to become a prognostic indicator for chemotherapy response in patients with PC.

Position of Circulating Tumor Cells in the Clinical Routine in Prostate Cancer and Breast Cancer Patients

Simple Summary

Many different therapies are applied to fight tumor disease. Blood-based biosources, like circulating tumor cells (CTCs), offer the opportunity to monitor the healing progression and the real-time response to the therapy. In this review, we analyze the outcomes of the clinical trials and scientific studies of prostate and breast cancer performed in the decade between April 2010 and April 2020. Additionally, we describe the abstracts from the 4th Advances in Circulating Tumor Cells (ACTC) meeting in 2019. We discuss the potential therapeutic opportunities related to the CTCs and the challenges ahead in the routine treatment of cancer.

Abstract

Prostate cancer and breast cancer are the most common cancers worldwide. Anti-tumor therapies are long and exhaustive for the patients. The real-time monitoring of the healing progression could be a useful tool to evaluate therapeutic response. Blood-based biosources like circulating tumor cells (CTCs) may offer this opportunity. Application of CTCs for the clinical diagnostics could improve the sequenced screening, provide additional valuable information of tumor dynamics, and help personalized management for the patients. In the past decade, CTCs as liquid biopsy (LB) has received tremendous attention. Many different isolation and characterization platforms are developed but the clinical validation is still missing. In this review, we focus on the clinical trials of circulating tumor cells that have the potential to monitor and stratify patients and lead to implementation into clinical practice.

Analysis of AR/ARV7 Expression in Isolated Circulating Tumor Cells of Patients with Metastatic Castration-Resistant Prostate Cancer (SAKK 08/14 IMPROVE Trial)

Despite several treatment options and an initial high response rate to androgen deprivation therapy, the majority of prostate cancers will eventually become castration-resistant in the metastatic stage (mCRPC). Androgen receptor splice variant 7 (ARV7) is one of the best-characterized androgen receptor (AR) variants whose expression in circulating tumor cells (CTCs) has been associated with enzalutamide resistance. ARV7 expression analysis before and during enzalutamide treatment could identify patients requiring alternative systemic therapies. However, a robust test for the assessment of the ARV7 status in patient samples is still missing. Here, we implemented an RT-qPCR-based assay for detection of AR full length (ARFL)/ARV7 expression in CTCs for clinical use. Additionally, as a proof-of-principle, we validated a cohort of 95 mCRPC patients initiating first line treatment with enzalutamide or enzalutamide/metformin within a clinical trial. A total of 95 mCRPC patients were analyzed at baseline of whom 27.3% (26/95) had ARFL+ARV7+, 23.1% (22/95) had ARFL+ARV7−, 23.1% (22/95) had ARFL−ARV7−, and 1.1% (1/95) had ARFL−ARV7+ CTCs. In 11.6% (11/95), no CTCs could be isolated. A total of 25/95 patients had another CTC analysis at progressive disease, of whom 48% (12/25) were ARV7+. Of those, 50% (6/12) were ARV7− and 50% (6/12) were ARV7+ at baseline. Our results show that mRNA analysis of isolated CTCs in mCRPC is feasible and allows for longitudinal endocrine agent response monitoring and hence could contribute to treatment optimization in mCRPC.

Fractional uptake of circulating tumor cells into liver-lung compartments during curative resection of periampullary cancer

Circulating tumor cells (CTCs) are able to predict outcome in patients with breast, colon and prostate cancer and appear to be promising biomarkers of pancreatic carcinoma. The aim of the present study was to demonstrate a statistically significant portal-arterial difference of CTCs during curative resection of periampullary cancer. A commercially available instrument (Isoflux^R) was used to quantify blood content of CTC in 10 patients with periampullary cancer according to preoperative diagnostics. Portal and arterial blood samples (~8 ml each) were simultaneously collected intra-operatively following surgical dissection prior to division of the pancreas for tumor removal. Quantitative CTC analyses were performed according to standardized protocols for immune-magnetic enrichment of CTC. Flow cytometry was applied for qualitative evaluations of various CTC markers in 7 patients. There was a statistically significant difference in the number of CTCs collected in the portal blood [58±14 cells per 100 ml; mean ± standard error (SE)] vs. arterial blood [24±7 cells per 100 ml (SE), P<0.025]. A fractional uptake of ≥40% across liver and lung compartments of assumed malignant CTC was estimated to correspond to the appearance of ~410 tumor cells per minute during pancreatic resections based on estimated hepatic blood flow, measured tumor cell mass and tumor cell proliferation activity. Complications in the collection of portal blood were not observed. A significant uptake across liver or lung compartments of potentially malignant tumor CTCs from periampullary carcinoma may represent a model to capture, define and characterize cell clones with metastatic potential in liver and lung tissues following surgical resection.

Circulating tumor cells and survival in abiraterone- and enzalutamide-treated patients with castration-resistant prostate cancer

BACKGROUND

The outcome to treatment administered to patients with metastatic castration-resistant prostate cancer (mCRPC) greatly differs between individuals, underlining the need for biomarkers guiding treatment decision making.

OBJECTIVE

To investigate the prognostic value of circulating tumor cell (CTC) enumeration and dynamics, in the context of second-line endocrine therapies (ie, abiraterone acetate or enzalutamide), irrespective of prior systemic therapies.

DESIGN, SETTINGS, AND PARTICIPANTS

In a prospective, multicentre study blood samples for CTC enumeration were collected from patients with mCRPC at baseline (n = 174). In patients who responded for minimally 10-12 weeks a follow-up sample was collected.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

For baseline analysis, patients were stratified in <5 or ≥5 CTCs/7.5 mL, whereas for the analysis of CTC dynamics at 10-12 weeks, in patients with stable, increasing or decreasing CTC counts. Progression-free survival (PFS), overall survival (OS), and PSA changes at 10-12 weeks were compared between groups.

RESULTS

Patients demonstrating increasing CTCs on therapy had a shorter median PFS (4.03 vs 12.98 vs 13.67 months, HR 3.6, 95%CI 1.9-6.8; P < 0.0001) and OS (11.2 months vs not reached, HR 9.5, 95%CI 3.7-24; P < 0.0001), compared to patients with decreasing or stable CTCs. Multivariable Cox regression showed that prior chemotherapy (HR 4.1, 95%CI 1.9-8.9; P = 0.0003), a high baseline CTC count (HR 1.5, 95%CI 1.2-1.9; P = 0.002) and increasing CTCs at follow-up (HR 3.3, 95%CI 1.4-7.6; P = 0.005) were independent predictors of worse PFS. Previous chemotherapy (HR 7, 95%CI 1.9-25; P = 0.003), high baseline CTC counts (HR 2.2, 95%CI 1.4-3.7; P = 0.002) and increasing CTCs during therapy (HR 4.6, 95%CI 1.4-15; P = 0.01) were independently associated with shorter OS. ≥30% and ≥50% PSA responses less frequently occurred in patients with CTC inclines at 10-12 weeks on therapy (χ² test: P < 0.01).

CONCLUSIONS

CTC dynamics during therapy are associated with PSA response and provide independent clinical prognostication over PSA declines. Hence the study demonstrates the pharmacodynamic properties of CTCs.

EMT circulating tumor cells detected by cell-surface vimentin are associated with prostate cancer progression

Recent advances in the field of circulating tumor cells (CTC) have shown promise in this liquid biopsy-based prognosis of patient outcome. However, not all of the circulating cells are tumor cells, as evidenced by a lack of tumor-specific markers. The current FDA standard for capturing CTCs (CellSearch) relies on an epithelial marker and cells captured via CellSearch cannot be considered to have undergone EMT. Therefore, it is difficult to ascertain the presence and relevance of any mesenchymal or EMT-like CTCs. To address this gap in technology, we recently discovered the utility of cell-surface vimentin (CSV) as a marker for detecting mesenchymal CTCs from sarcoma, breast, and colon cancer. Here we studied peripheral blood samples of 48 prostate cancer (PCA) patients including hormone sensitive and castration resistant sub-groups. Blood samples were analyzed for three different properties including our own CSV-based CTC enumeration (using 84-1 mAb against CSV), CellSearch-based epithelial CTC counts, and serum prostate-specific antigen (PSA) quantification. Our data demonstrated that in comparison with CellSearch, the CSV-based method had greater sensitivity and specificity. Further, we observed significantly greater numbers of CTCs in castration resistant patients as measured by our CSV method but not CellSearch. Our data suggests CSV-guided CTC enumeration may hold prognostic value and should be further validated as a possible measurement of PCA progression towards the deadly, androgen-independent form.

Comparison of Timed Automata with Discrete Event Simulation for Modeling of Biomarker-Based Treatment Decisions: An Illustration for Metastatic Castration-Resistant Prostate Cancer

BACKGROUND

With the advent of personalized medicine, the field of health economic modeling is being challenged and the use of patient-level dynamic modeling techniques might be required.

OBJECTIVES

To illustrate the usability of two such techniques, timed automata (TA) and discrete event simulation (DES), for modeling personalized treatment decisions.

METHODS

An early health technology assessment on the use of circulating tumor cells, compared with prostate-specific antigen and bone scintigraphy, to inform treatment decisions in metastatic castration-resistant prostate cancer was performed. Both modeling techniques were assessed quantitatively, in terms of intermediate outcomes (e.g., overtreatment) and health economic outcomes (e.g., net monetary benefit). Qualitatively, among others, model structure, agent interactions, data management (i.e., importing and exporting data), and model transparency were assessed.

RESULTS

Both models yielded realistic and similar intermediate and health economic outcomes. Overtreatment was reduced by 6.99 and 7.02 weeks by applying circulating tumor cell as a response marker at a net monetary benefit of -€1033 and -€1104 for the TA model and the DES model, respectively. Software-specific differences were observed regarding data management features and the support for statistical distributions, which were considered better for the DES software. Regarding method-specific differences, interactions were modeled more straightforward using TA, benefiting from its compositional model structure.

CONCLUSIONS

Both techniques prove suitable for modeling personalized treatment decisions, although DES would be preferred given the current software-specific limitations of TA. When these limitations are resolved, TA would be an interesting modeling alternative if interactions are key or its compositional structure is useful to manage multi-agent complex problems.

Circulating tumor cells in prostate cancer: Precision diagnosis and therapy

The primary cause of tumor-associated mortality in prostate cancer (PCa) remains distant metastasis. The dissemination of tumor cells from the primary tumor to distant sites through the bloodstream cannot be detected early by standard imaging methods. Circulating tumor cells (CTCs) represent an effective prognostic and predictive biomarker, which are able to monitor efficacy of adjuvant therapies, detect early development of metastases, and finally, assess therapeutic responses of advanced disease earlier than traditional diagnostic methods. In addition, since repeated tissue biopsies are invasive, costly and not always feasible, the assessment of tumor characteristics on CTCs, by a peripheral blood sample as a liquid biopsy, represents an attractive opportunity. The implementation of molecular and genomic characterization of CTCs may contribute to improve the treatment selection and thus, to move toward more precise diagnosis and therapy in PCa. The present study summarizes the current advances in CTC enrichment and detection strategies and reviews how CTCs may contribute to significant insights in the metastatic process, as well as how they may be utilized in clinical application in PCa. Although it is proposed that CTCs may offer insights into the prognosis and management of PCa, there are a number of challenges in the study of circulating tumor cells, and their clinical utility remains under investigation.

Circulating Tumor Cell and Cell-free Circulating Tumor DNA in Lung Cancer

Circulating tumor cells (CTCs) are tumor cells that are separated from the primary site or metastatic lesion and disseminate in blood circulation. CTCs are considered to be part of the long process of cancer metastasis. As a 'liquid biopsy', CTC molecular examination and investigation of single cancer cells create an important opportunity for providing an understanding of cancer biology and the process of metastasis. In the last decade, we have seen dramatic development in defining the role of CTCs in lung cancer in terms of diagnosis, genomic alteration determination, treatment response and, finally, prognosis prediction. The aims of this review are to understand the basic biology and to review methods of detection of CTCs that apply to the various types of solid tumor. Furthermore, we explored clinical applications, including treatment monitoring to anticipate therapy resistance as well as biomarker analysis, in the context of lung cancer. We also explored the potential use of cell-free circulating tumor DNA (ctDNA) in the genomic alteration analysis of lung cancer.

A 2-Gene Panel Derived From Prostate Cancer-Enhanced Transcripts in Whole Blood Is Prognostic for Survival and Predicts Treatment Benefit in Metastatic Castration-Resistant Prostate Cancer

BACKGROUND

To determine a prognostic model derived from prostate cancer-enhanced transcripts in whole blood of castration-resistant prostate cancer (CRPC) patients and explore its applicability as a surrogate of treatment response.

METHODS

Six out of twenty-three selected transcripts were identified as specific for detection of metastatic prostate cancer cells in peripheral blood using quantitative polymerase chain reaction (qPCR). Their prognostic value was explored in whole blood samples of a training cohort (n = 22 CRPC patients, New York, USA). A resulting 2-gene panel (2GP) including KLK2 and TMPRSS2 was validated in an independent cohort with pre- and post-treatment blood draws after 9-16 weeks of systemic treament (n = 86 CRPC patients, Munich, Germany). Overall survival (OS), prostate-specific antigen progression-free survival (PSA-PFS), and clinical PFS were analyzed. Kaplan-Meier and cox regression analyses were performed.

RESULTS

An unfavorable 2GP (≥1 marker positive) identified patients with poor survival (median OS 10.0 months [95%CI 5.7-14.2] vs. not reached; P = 0.023). This was validated in an independent cohort at pre-treatment (median OS 7.8 [95%CI 6.5-9.2] vs. 17.3 months [95%CI 10.7-23.8]; P = 0.004) and post-treatment blood draw (median OS 5.0 [95%CI 0.0-10.0] vs. 18.0 months [95%CI 9.5-26.6]; P = 0.003). The 2GP independently predicted OS on multivariate analysis (hazard ratio 2.1 [95%CI 1.1-4.0]; P = 0.034) and performed better than PSA decline at correlation with OS. Conversion to favorable 2GP during treatment correlated with improved OS (7.8 to 20.9 months), PSA-PFS (2.8 to 12.0 months), and clinical PFS (4.6 to 8.0 months).

CONCLUSIONS

The established 2GP is prognostic for survival at pre- and post-treatment blood draw in CRPC patients and conversion to favorable 2GP predicts treatment benefit. Prostate 76:1160-1168, 2016. © 2016 Wiley Periodicals, Inc.

Prospective evaluation of [11C]Choline PET/CT in therapy response assessment of standardized docetaxel first-line chemotherapy in patients with advanced castration refractory prostate cancer

PURPOSE

The aim of this study was to prospectively evaluate the value of [¹¹C] Choline PET/CT in monitoring early and late response to a standardized first-line docetaxel chemotherapy in castration refractory prostate cancer (mCRPC) patients.

METHODS

Thirty-two patients were referred for [¹¹C] Choline PET/CT before the start of docetaxel chemotherapy, after one and ten chemotherapy cycles (or - in case of discontinuation - after the last administered cycle) for therapy response assessment. [¹¹C] Choline uptake (SUV_max, SUV_mean), CT derived Houndsfield units (HU_max, HU_mean), and volume of bone, lung, and nodal metastases and local recurrence were measured semi-automatically at these timepoints. Change in SUV_max, SUV_mean, HU_max, HU_mean, and volume was assessed between PET 2 and 1 (early response assessment, ERA) and PET 3 and 1 (late response assessment, LRA) on a patient and lesion basis. Results of PET/CT were compared to clinically used RECIST 1.1 and clinical criteria based therapy response assessment including PSA for defining progressive disease (PD) and non-progressive disease (nPD), respectively. Relationships between changes of SUV_max and SUV_mean (early and late) and changes of PSA_early and PSA_late were evaluated. Prognostic value of initial SUV_max and SUV_mean was assessed. Statistical analyses were performed using SPSS.

RESULTS

In the patient-based ERA and LRA there were no statistically significant differences in change of choline uptake, HU, and volume between PD and nPD applying RECIST or clinical response criteria. In the lesion-based ERA, decrease in choline uptake of bone metastases was even higher in PD (applying RECIST criteria), whereas in LRA the decrease was higher in nPD (applying clinical criteria). There were only significant correlations between change in choline uptake and PSA in ERA in PD, in LRA no significant correlations were discovered. Initial SUV_max and SUV_mean were statistically significantly higher in nPD (applying clinical criteria).

CONCLUSION

There is no significant correlation between change in choline uptake in [¹¹C] Choline PET/CT and clinically routinely used objective response assessment during the early and late course of docetaxel chemotherapy. Therefore, [¹¹C] Choline PET/CT seems to be of limited use in therapy response assessment in standardized first-line chemotherapy in mCRPC patients.

The use of circulating tumor cells in guiding treatment decisions for patients with metastatic castration-resistant prostate cancer

The therapeutic landscape of metastatic castration-resistant prostate cancer (mCRPC) has drastically changed over the past decade with the advent of several new anti-tumor agents. Oncologists increasingly face dilemmas concerning the best treatment sequence for individual patients since most of the novel compounds have been investigated and subsequently positioned either pre- or post-docetaxel. A currently unmet need exists for biomarkers able to guide treatment decisions and to capture treatment resistance at an early stage thereby allowing for an early change to an alternative strategy. Circulating tumor cells (CTCs) have in this context intensively been investigated over the last years. The CTC count, as determined by the CellSearch System (Janssen Diagnostics LLC, Raritan, NJ), is a strong, independent prognostic factor for overall survival in patients with mCRPC at various time points during treatment and, as an early response marker, outperforms traditional response evaluations using serum prostate specific antigen (PSA) levels, scintigraphy as well as radiography. The focus of research is now shifting toward the predictive value of CTCs and the use of the characterization of CTCs to guide the selection of treatments with the highest chance of success for individual patients. Recently, the presence of the androgen receptor splice variant 7 (AR-V7) has been shown to be a promising predictive factor. In this review, we have explored the clinical value of the enumeration and characterization of CTCs for the treatment of mCRPC and have put the results obtained from recent studies investigating the prognostic and predictive value of CTCs into clinical perspective.

Whole blood defensin mRNA expression is a predictive biomarker of docetaxel response in castration-resistant prostate cancer

This study tested the potential of circulating RNA-based signals as predictive biomarkers for docetaxel response in patients with metastatic castration-resistant prostate cancer (CRPC). RNA was analyzed in blood from six CRPC patients by whole-transcriptome sequencing (total RNA-sequencing) before and after docetaxel treatment using the Illumina’s HiSeq platform. Targeted RNA capture and sequencing was performed in an independent cohort of ten patients with CRPC matching the discovery cohort to confirm differential expression of the genes. Response to docetaxel was defined on the basis of prostate-specific antigen levels and imaging criteria. Two-way analysis of variance was used to compare differential gene expression in patients classified as responders versus nonresponders before and after docetaxel treatment. Thirty-four genes with two-fold differentially expressed transcripts in responders versus nonresponders were selected from total RNA-sequencing for further validation. Targeted RNA capture and sequencing showed that 13/34 genes were differentially expressed in responders. Alpha defensin genes DEFA1, DEFA1B, and DEFA3 exhibited significantly higher expression in responder patients compared with nonresponder patients before administration of chemotherapy (fold change >2.5). In addition, post-docetaxel treatment significantly increased transcript levels of these defensin genes in responders (fold change >2.8). Our results reveal that patients with higher defensin RNA transcripts in blood respond well to docetaxel therapy. We suggest that monitoring DEFA1, DEFA1B, and DEFA3 RNA transcripts in blood prior to treatment will be helpful to determine which patients are better candidates to receive docetaxel chemotherapy.