Management of Progressive Metastatic Castration-Resistant Prostate Cancer

Introduction to Treatment Options

The National Comprehensive Cancer Network recommends immediately discontinuing bicalutamide and switching to enzalutamide or abiraterone plus prednisone as first-line therapy for castration-resistant prostate cancer (CRPC), while continuing LHRH agonist/antagonist therapy and initiating mandatory bone-protective therapy with denosumab or zoledronic acid 1, 2, 3

Enzalutamide demonstrates superior efficacy compared to bicalutamide, with median time to progression of 15.7 months versus 5.8 months for bicalutamide (HR 0.44), representing a 76% reduction in risk of progression or death (HR 0.24) 1, 3
The National Comprehensive Cancer Network recommends enzalutamide as a category 1, preferred treatment for patients with metastatic CRPC without prior novel hormone therapy 1, 3
Enzalutamide has no significant cardiovascular concerns compared to placebo, with major adverse cardiovascular events occurring in only 5% versus 3% on placebo 1, 3
Common side effects of enzalutamide include fatigue (33-34%), diarrhea (21%), hot flushes (20%), hypertension (12%), and headache (12%), with seizure risk remaining low at 0.6-0.9% 1, 3
Abiraterone is a category 1 recommendation for post-docetaxel CRPC and category 2A for pre-chemotherapy asymptomatic/minimally symptomatic CRPC 4, 5

The National Comprehensive Cancer Network recommends denosumab 120 mg subcutaneously every 4 weeks as a preferred option for bone-protective therapy, which is superior to zoledronic acid in delaying skeletal-related events (HR 0.82, P=0.0002) 2, 7
Zoledronic acid 4 mg intravenously every 3-4 weeks is an alternative option, with dose adjustment required for renal impairment (not recommended if creatinine clearance <30 mL/min) 6, 2

Urgent spine MRI is recommended if any back pain or neurological symptoms occur to rule out spinal cord compression, which occurs in approximately 95% of patients with metastatic spinal cord compression 7
Restaging with CT and bone scan is recommended before initiating new therapy 8
Baseline PSA, testosterone level, liver function tests, and complete blood count are recommended, with monitoring of PSA and clinical examinations every 3 months 1, 5, 8

If progression occurs on enzalutamide or abiraterone, the National Comprehensive Cancer Network recommends considering docetaxel 75 mg/m² every 3 weeks, radium-223 for symptomatic bone metastases, or sipuleucel-T if not previously received 4, 2
For patients with prior docetaxel, cabazitaxel or alternative novel hormone therapy (abiraterone if received enzalutamide, or vice versa) are recommended 5, 6

Median survival for metastatic CRPC is less than 2 years, with time to castration resistance averaging 14-30 months from ADT initiation 2
More than 90% of CRPC patients have bone metastases, and early referral to palliative care services is recommended for symptom management and quality of life optimization 2, 8