Reviews/Targeted Therapy Prostate Cancer/Androgen receptor splice variant 7 predicts androgen receptor inhibitor resistance
Resistance · PC-RES-01 · v2
Borderline: within 4 points of the Established/Likely boundary, so a re-grade could land either side.
Several studies that followed men with advanced prostate cancer measured a short form of the androgen receptor, called AR-V7, in tumour cells circulating in the blood before starting enzalutamide or abiraterone. Men who tested positive consistently did far worse on these two drugs: they rarely saw their PSA fall and their disease progressed sooner [1][3]. The same groups showed that these positive men tended to live longer if given chemotherapy (a taxane) instead, so the signal appears specific to this drug class [2][5][12]. A dedicated multicentre study that blinded the analysis and used two different tests reached the same conclusion [3]. The panel treated the association as well supported, while noting it is not an all-or-nothing effect, the studies are observational rather than randomised, and the tests used do not all agree with one another.
The corpus demonstrates a consistent, independently replicated association between blood-based CTC AR-V7 positivity and poor outcomes on enzalutamide and abiraterone: 0% PSA response in AR-V7-positive men versus 53% and 68% in the original prospective cohort [1], and independent association with shorter PFS and OS in the blinded multicentre PROPHECY validation across two assays [3]. The association is framed explicitly as primary resistance and is drug-class specific, with no equivalent association seen for taxanes [5]. Treatment-specificity is reinforced by survival favouring taxanes over ARS inhibitors in AR-V7-positive men [2][12]. Convergent variant-biology support comes from AR-V9, coexpressed with AR-V7, predicting abiraterone resistance [16]. The contested point: The division is not over whether the association exists but over how absolute and how mechanistically specific it is: PROPHECY records residual PSA responses of 0% to 11% in positive men, so positivity marks high likelihood rather than categorical resistance [3]. Whether AR-V7 is a drug-specific resistance mechanism or partly a marker of advanced disease is unresolved, since prevalence rises from 3% first-line to 31% third-plus line [2].
All 16 papers behind this claim with their DOIs and what each does to it, the panel’s arbitration, the evidence gap map and the open research questions. Free, and sent to your inbox.
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The association is not categorical: PROPHECY [3] reports AR-V7-positive men still had confirmed PSA responses of 0% to 11%, so AR-V7 positivity marks high likelihood, not absolute, primary resistance.
Possible confounding by disease stage/line of therapy: AR-V7 prevalence rises with line (3% first-line to 31% third-plus line in [2]), so AR-V7 may partly track tumour burden/advanced disease rather than a drug-specific resistance mechanism; adjustment is only partial.
Where it remains uncertain. The effect is strong but not categorical, with 0% to 11% confirmed PSA responses still seen in positive men [3], and prevalence rising with line of therapy from 3% to 31% [2] raises possible confounding by disease stage.
Aleatory
AR-V7-positive men still show confirmed PSA responses of 0% to 11% [3] and median outcomes vary within groups, so positivity is probabilistic, not deterministic.
The load-bearing papers from a corpus of 16, each classified by what it does to the claim. Every DOI is taken from the corpus the claim was graded on.
Index prospective finding of AR-V7 CTC association with resistance to enzalutamide (and, parallel data, abiraterone).
“The association between AR-V7 detection and therapeutic resistance was maintained after adjustment for expression of full-length androgen receptor messenger RNA.”
Panel auditInternal validity: medium · scope of inference: Men with mCRPC initiating enzalutamide or abiraterone, baseline CTC AR-V7 mRNA status.Key limitations: small sample · single institution · authors call for validation
Independent group (MSKCC) replication using a nuclear AR-V7 protein CTC assay.
“Patients whose samples had AR-V7-positive CTCs before ARS inhibition had resistant posttherapy PSA changes (PTPC), shorter rPFS, shorter time on therapy, and shorter OS than those without AR-V7-positive CTCs.”
Panel auditInternal validity: medium · scope of inference: Men with progressive mCRPC changing therapy, CTC AR-V7 protein status before ARS inhibitor or taxane.Key limitations: no p value for the key within-ARS comparison · mixed treatment lines
Prospective multicentre blinded validation across two independent assays — the strongest confirmation of the association.
“AR-V7 detection by both the Johns Hopkins and Epic AR-V7 assays was independently associated with shorter PFS (hazard ratio, 1.9 [95% CI, 1.1 to 3.3; P = .032] and 2.4 [95% CI, 1.1 to 5.1; P = .020], respectively) and OS (hazard ratio, 4.2 [95% CI, 2.1 to 8.5] and 3.5 [95% CI, 1.6 to 8.1], respectively) after adjusting for CTC number and clinical prognostic factors.”
Panel auditInternal validity: high · scope of inference: High-risk men with mCRPC starting abiraterone or enzalutamide, baseline CTC AR-V7 status.Key limitations: high-risk population only · moderate sample size
Convergent variant-biology support linking AR-V7-associated variants to abiraterone resistance (predictive quantity is AR-V9).
“AR-V9 was frequently coexpressed with AR-V7.”
Panel auditInternal validity: medium · scope of inference: CRPC-stage patients initiating abiraterone, AR-variant mRNA in metastatic tissue and CTCs.Key limitations: resistance HR is for AR-V9 not AR-V7 · no isolated AR-V7 contrast
4 of 16 papers shown. The full review lists all of them, with the panel’s arbitration →
Claims are graded at each quarterly release, and re-graded between releases only when a pivotal trial lands. Every change is a new version of the claim.
Independent prospective replication including a dedicated blinded multicentre validation establishes the association, held just at the Established band edge by observational design and assay heterogeneity rather than any contradictory evidence.
Release 2026-q4 re-graded every claim from its corpus under protocol v0.19. An earlier release's grade is shown for the record; it came from an earlier protocol and is not a movement.
Assumptions that carry weight but are not themselves established.
The panel records the gap that would most move the claim, and the study that would close it.
No randomised biomarker-stratified trial. Every included study is observational [1][2][3][5][12], so AR-V7 remains an association and cannot be read as a validated causal resistance mechanism for treatment decisions. The panel rates this the highest-importance open gap for the claim, and names the study design that would close it: A prospective trial randomising CTC AR-V7-positive men to ARS inhibitor versus taxane with PFS and OS endpoints.
Open question: Does selecting treatment by CTC AR-V7 status improve survival compared with standard sequencing? Why it is still open: All corpus evidence is correlative [1][2][3][5][12]; no interventional biomarker-stratified comparison is present.
Priors is a sceptical first reader, not peer review, and not medical advice.
Release 2026-q4 · graded 26 Oct 2026 · protocol v0.19