Definition of Metastatic Castrate-Resistant Prostate Cancer (mCRPC)
Metastatic castrate-resistant prostate cancer is defined as prostate cancer that demonstrates clinical, radiographic, or biochemical progression despite maintaining castrate levels of serum testosterone (<50 ng/dL or <1.7 nmol/L), with evidence of distant metastases on imaging studies. 1
Core Diagnostic Criteria
The diagnosis of mCRPC requires three essential components to be present simultaneously:
1. Castrate Testosterone Environment
- Serum testosterone must be <50 ng/dL (<1.7 nmol/L) 1
- This must be laboratory-confirmed, not assumed
- Patients progressing on ADT should have testosterone levels verified before declaring castration resistance 1
2. Evidence of Disease Progression
Progression can be demonstrated through any one or more of the following:
Biochemical progression:
- PSA increase of >25% from nadir over baseline
- Requires two consecutive measurements at least one week apart
- Absolute PSA value must be >2.0 ng/mL 1, 2
Radiographic progression:
- New or enlarging soft tissue lesions (using RECIST criteria adapted for prostate cancer)
- Two or more new bone lesions on bone scan
- Can be detected by conventional imaging (CT, MRI, bone scan) or advanced imaging (PSMA-PET) 1, 2
Clinical progression:
- Symptomatic deterioration attributable to disease progression
- Development of new metastatic complications
3. Documented Metastatic Disease
- Presence of distant metastases confirmed on imaging studies
- This distinguishes mCRPC from non-metastatic CRPC (M0 CRPC) 1
- PSMA-PET imaging may detect metastases earlier and more sensitively than conventional imaging 3, 2
Critical Management Point
ADT must be continued indefinitely in patients with mCRPC to maintain castrate testosterone levels, even as the disease progresses and additional therapies are added 1. This is accomplished through continued orchiectomy or LHRH agonist/antagonist therapy.
Important Clinical Nuances
The mode of progression (biochemical vs. radiographic vs. both) does not significantly impact survival outcomes 3, though patients progressing biochemically tend to have higher PSA levels at progression (15 ng/mL) compared to those progressing radiographically (2 ng/mL) 3.
Common pitfall: Assuming castration resistance without confirming castrate testosterone levels—always verify testosterone <50 ng/dL before diagnosing CRPC 1. Some patients may have inadequate testosterone suppression from their current ADT regimen rather than true castration resistance.