Prostate cancer is the most commonly diagnosed cancer in men and the second leading cause of cancer-related death, accounting for 27% of new cancer diagnoses in men each year.
The standard initial treatment for advanced prostate cancer is androgen deprivation therapy (ADT), which suppresses the male hormones that fuel tumor growth. Many patients also receive additional drugs such as docetaxel or newer hormone-targeting agents alongside ADT.
Despite initial responses, most patients eventually develop metastatic castration-resistant prostate cancer (mCRPC) -- a stage where the disease continues to grow even when testosterone levels are kept very low. This is defined by rising PSA (prostate-specific antigen) levels on three consecutive tests or visible tumor progression on imaging.
mCRPC carries a significantly worse outlook than hormone-sensitive disease, making it the focus of intense research into new treatment strategies. This review summarizes currently approved therapies and promising experimental drugs.
Taxane chemotherapy -- specifically docetaxel and cabazitaxel -- forms the backbone of treatment for many patients with mCRPC. These drugs work by blocking the breakdown of cell scaffolding structures called microtubules, effectively halting cell division and triggering cancer cell death.
Two landmark trials, SWOG 99-16 and TAX 327, established docetaxel as a standard treatment, showing median overall survival of approximately 18 months compared to about 16 months for older chemotherapy drugs. The every-three-weeks dosing schedule proved more effective than weekly dosing.
Cabazitaxel was developed for patients who progress after docetaxel because it shows less cross-resistance. The TROPIC trial showed it extended survival to 15.1 months versus 12.7 months with an older drug. The CARD trial further showed cabazitaxel outperformed hormone-targeting drugs in patients who had already received prior hormonal therapy.
For patients with aggressive disease features (such as visceral metastases, low PSA with bulky tumors, or specific genetic defects in PTEN, TP53, and RB1), combining cabazitaxel with carboplatin has shown some benefit in early trials, although this approach is still being studied.
Androgen receptor axis targeted therapies (ARATs) are drugs that block testosterone's ability to activate prostate cancer cells, even when testosterone levels are already very low. The two most widely used are abiraterone acetate and enzalutamide.
Abiraterone acetate works by blocking an enzyme called CYP17A1, which is critical for producing androgens throughout the body and inside the tumor itself. It must be taken with a corticosteroid to prevent a side effect involving salt imbalance. Phase III trials demonstrated it extended median overall survival by roughly 3-4 months compared to placebo, both before and after chemotherapy.
Enzalutamide acts differently by directly blocking the androgen receptor at multiple steps: it prevents testosterone from binding, stops the activated receptor from entering the cell nucleus, and blocks it from attaching to DNA. The AFFIRM trial showed a 37% reduction in death risk, and the PREVAIL trial confirmed its benefit even in patients who had not yet received chemotherapy.
Both drugs are now considered standard treatment options at multiple stages of mCRPC, and the choice between them depends largely on prior treatments, patient health status, and individual tumor characteristics.
Radium-223 is a radioactive element that mimics calcium and naturally travels to areas of active bone formation, which are common sites of prostate cancer spread. Once there, it emits high-energy alpha particles that damage cancer cell DNA with minimal harm to surrounding tissue. The ALSYMPCA trial showed it extended survival to 14.9 months versus 11.3 months with placebo in patients with bone-only metastases.
However, combining radium-223 with abiraterone increased fracture risk and was found to be harmful, leading to restrictions on its use. Current guidelines require patients to have received at least two prior systemic treatments before using radium-223.
Lutetium-177-PSMA-617 (177Lu-PSMA-617) represents a newer approach called theragnostics -- combining diagnostics with treatment. It targets a protein called PSMA (Prostate Specific Membrane Antigen) that is highly expressed on prostate cancer cells. The radioactive lutetium is attached to a molecule that binds PSMA, delivering targeted radiation directly into cancer cells.
The landmark VISION trial enrolled 831 patients who had already received chemotherapy and hormonal therapy. Those treated with 177Lu-PSMA-617 lived a median of 15.3 months versus 11.3 months for standard care, with significantly delayed disease progression. A PSMA-positive result on a specialized PET scan is required before treatment.
Approximately 10-25% of mCRPC patients carry mutations in homologous recombination repair (HRR) genes -- the cellular machinery that fixes certain types of DNA damage. The most important mutations are in BRCA1, BRCA2, and ATM. These defects make cancer cells reliant on an alternative repair enzyme called PARP.
PARP inhibitors block this backup repair system. When both repair pathways are disabled, cancer cells accumulate so much DNA damage that they die -- a concept called synthetic lethality. This approach spares normal cells, which retain functional HRR pathways.
Olaparib became the first approved PARP inhibitor for prostate cancer following the PROfound trial, which showed it significantly extended progression-free survival (7.4 vs 3.6 months) in patients with BRCA1, BRCA2, or ATM mutations who had progressed on hormonal therapy. It has also been approved in combination with abiraterone as first-line mCRPC treatment, even without confirmed HRR mutations.
Other PARP inhibitors under study include rucaparib (TRITON2 trial, 43.5% objective response rate in BRCA-mutated patients) and talazoparib (TALAPRO-1, 29.8% response rate). The MAGNITUDE trial confirmed that combining niraparib with abiraterone benefits patients who carry HRR mutations, particularly those with BRCA1/2 alterations, but not patients without these mutations.
The PI3K/AKT/mTOR signaling pathway is overactive in up to 70% of advanced prostate cancers, often because of loss of a tumor suppressor called PTEN. This pathway drives uncontrolled cell growth. AKT inhibitors like ipatasertib and capivasertib block this pathway.
The IPAtential150 phase III trial tested ipatasertib combined with abiraterone in over 1,100 patients. In the subgroup with PTEN loss confirmed by lab testing, ipatasertib extended progression-free survival (18.5 vs 16.5 months), though the benefit was modest. In the general patient population without selecting for PTEN loss, no statistically significant benefit was seen.
Immunotherapy with immune checkpoint inhibitors has had limited success in unselected mCRPC patients because prostate tumors tend to have low mutation rates and suppressive immune environments -- making them what researchers call an immunologically cold tumor. However, patients with specific genetic features like microsatellite instability (MSI-H) or mismatch repair deficiency (dMMR) may benefit.
Pembrolizumab (anti-PD-1) showed low response rates of only 3-5% in unselected patients in the KEYNOTE-199 trial, but the FDA approved it specifically for the MSI-H/dMMR subgroup. Combination approaches pairing checkpoint inhibitors with chemotherapy or tyrosine kinase inhibitors like cabozantinib are still under investigation.
Bone metastases are one of the most common and debilitating features of mCRPC, causing fractures, spinal cord compression, and severe pain -- collectively called skeletal-related events (SREs). Several drugs have been developed specifically to reduce these complications.
Zoledronic acid, a bisphosphonate drug that inhibits bone destruction, reduced the proportion of patients experiencing at least one SRE from 49% to 38% and extended the time to the first SRE by approximately six months in a randomized trial. It did not, however, improve overall survival.
Denosumab is a targeted antibody that blocks RANKL, a key protein that drives osteoclast activity and bone breakdown in cancer-affected bone. Compared directly with zoledronic acid, denosumab delayed time to first SRE longer (20.7 vs 17.1 months). Both drugs carry risks of jaw bone death (osteonecrosis) and calcium deficiency.
Current guidelines recommend either zoledronic acid or denosumab for mCRPC patients with bone metastases who are at significant risk for skeletal complications, with denosumab considered slightly superior based on the comparison trial data.
A growing challenge in mCRPC is selecting the right treatment for each individual patient. Predictive biomarkers -- measurable molecular features that indicate likely response to a specific treatment -- are central to this goal.
AR-V7 is a mutant form of the androgen receptor that remains active without needing testosterone to bind it. Detecting AR-V7 in circulating tumor cells predicts resistance to hormone-targeting drugs like enzalutamide and abiraterone, while these patients still tend to respond to taxane chemotherapy. This makes AR-V7 a potentially valuable tool for choosing between treatment classes, though it is not yet validated for routine clinical use.
Liquid biopsy -- analyzing tumor material shed into the bloodstream, including circulating tumor DNA (ctDNA), circulating tumor cells (CTCs), and small RNA molecules (miRNA) -- is emerging as a less invasive alternative to tissue biopsy. ctDNA analysis can track treatment response and detect emerging resistance mutations in real time.
PTEN loss, found in 40-50% of mCRPC patients, activates the AKT pathway and predicts poor responses to hormonal therapies while identifying patients who may benefit from AKT inhibitors like ipatasertib. HRR gene mutations (especially BRCA1/2) predict response to PARP inhibitors, and these biomarkers now guide treatment selection in clinical practice.
The treatment landscape for mCRPC has undergone dramatic transformation in recent years. What was once limited to docetaxel chemotherapy now includes hormone-targeting agents, PARP inhibitors, targeted radiation therapies, and emerging immunotherapy combinations.
Despite these advances, mCRPC remains a lethal disease with no curative treatments available for most patients. Resistance to virtually all current therapies eventually develops, driving the need for ongoing research into new drug targets and combination strategies.
The optimal sequencing of available therapies -- deciding which treatment to use first, second, and beyond -- remains an open question. The prior treatments a patient has received heavily influence what comes next, and cross-resistance between drugs can limit options over time.
The authors emphasize that the identification and validation of predictive biomarkers should be a top research priority, as they are essential for developing tailored treatment strategies that match the right drug to the right patient at the right time.