Time for action: actinium-225 PSMA-targeted alpha therapy for metastatic prostate cancer - a systematic review and meta-analysis

Rationale: Metastatic prostate cancer in the castration-resistant (mCRPC) setting remains challenging to treat. Prostate-specific membrane antigen (PSMA)-targeted alpha therapy (TAT) is emerging as a promising option. We aimed to systematically review the efficacy and safety of PSMA-TAT in patients with prostate cancer. Methods: A comprehensive search of PubMed/MEDLINE and EMBASE databases was conducted up to October 2024, adhering to the PRISMA guidelines. Selected studies were original research articles evaluating the efficacy and/or safety of PSMA-TAT including at least 10 patients. The outcomes measured included any prostate-specific antigen (PSA) response, ≥50% PSA reduction (PSA50), progression-free survival (PFS), overall survival (OS), and adverse events. PSA50 was pooled using a random-effects model, incorporating individual patient data on PSA50 and previous lines of treatment. Results: Eighteen studies involving 1,155 patients met the inclusion criteria. The majority included heavily pre-treated patients. The most commonly employed radiopharmaceutical was [²²⁵Ac]Ac-PSMA-617, in 15 studies. The pooled PSA50 response rate was 65% [95% Confidence interval (CI), 57-72%] with a moderate level of heterogeneity (I² = 81.17%, p < 0.001). Pooled response rates in patients who received none, one, and more than one prior line of treatment were 82% (95% CI, 73-90%), 72% (95% CI, 56-85%), and 55% (95% CI, 48-63%), respectively. PFS varied from 3 to 15 months, and OS from 8 to 31 months. Adverse events were predominantly mild (grades 1-2); severe adverse events (≥ grade 3) included anaemia (11%) and thrombocytopenia (6%). Conclusion: PSMA-TAT holds promising efficacy and an acceptable safety profile for treating metastatic prostate cancer. Randomised controlled trials are needed to optimise treatment protocols toward the implementation of PSMA-TAT into clinical practice.