Detecting predictive androgen receptor modifications in circulating prostate cancer cells.

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Androgen receptor (AR) modifications are a key mechanism of resistance to androgen deprivation therapy (ADT) in prostate cancer.
• Assessing these AR modifications is crucial for guiding treatment decisions, but obtaining tumor samples can be challenging.

Purpose of the Study:

• To develop and evaluate a method for simultaneously detecting common AR modifications (AR-V7 splice variant and AR point mutations) in circulating tumor cells (CTCs).
• To assess the clinical utility of detecting AR modifications in CTCs for predicting treatment response in prostate cancer patients with PSA progression.

Main Methods:

• A single-tube assay was developed combining immunomagnetic isolation of CTCs with quantitative real-time PCR and DNA pyrosequencing.
• The assay was prospectively applied to 47 patients with prostate cancer experiencing PSA progression.

Main Results:

• AR modifications were detected in 51% of patients with detectable CTCs.
• Seventeen patients had the AR-V7 splice variant, one had a p.T878A mutation, and one had both AR-V7 and a p.H875Y mutation.
• The estimated positive predictive value for therapy response/non-response based on CTC-AR status was approximately 94%.

Conclusions:

• Simultaneous detection of AR-V7 and AR point mutations in CTCs is feasible and provides valuable information for treatment selection.
• This approach has the potential to significantly improve prostate cancer treatment by enabling molecularly-informed therapy switches.
• The study estimated a substantial effect size (~27%) for molecularly-guided therapy adjustments, supporting its use in clinical trials.