Efficacy and safety of rechallenge therapy with [177Lu]Lu-PSMA in metastatic castration-resistant prostate cancer: a systematic review and meta-analysis.

Background Lutetium-177 PSMA radioligand therapy ([¹⁷⁷Lu]Lu-PSMA-RLT) is an effective treatment option for patients with metastatic castration-resistant prostate cancer (mCRPC). Prospective studies reported favourable efficacy and safety outcomes of up to 6 cycles of [¹⁷⁷Lu]Lu-PSMA. This study aimed to evaluate the efficacy and safety of [¹⁷⁷Lu]Lu-PSMA rechallenge therapy in patients with mCRPC who progressed after an initial course of [¹⁷⁷Lu]Lu-PSMA-RLT.Methods This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. A systematic search was performed using relevant keywords in PubMed, EMBASE, and Scopus from establishment to March 2025. Primary endpoints included biochemical responses with a decline in prostate-specific antigen (PSA) of more than 50% and any PSA decline. Secondary outcomes included survival outcomes and treatment-related toxicity following rechallenge therapy with [¹⁷⁷Lu]Lu-PSMA. A random-effects model was used to generate pooled proportions through meta-analysis.Results Eleven studies with 307 patients were included in the final analysis. Of these, 196 received 177Lu-PSMA RLT alone, and 111 received tandem 177Lu/225Ac-PSMA RLT. The pooled proportions of patients with more than a 50% PSA decline and any PSA decline were 0.45 (95% CI: 0.36-0.54) and 0.71 (95% CI: 0.61-0.80), respectively. In a total of 102 patients, 44 (43%) showed low-grade 1-2 xerostomia; however, no cases of serious xerostomia (grade ≥ 3) were reported. Moreover, the pooled proportion of patients experiencing grade ≥ 3 toxicity was 0.14 (95% CI: 0.09-0.19).Conclusion Rechallenge therapy with [¹⁷⁷Lu]Lu-PSMA is a feasible and safe treatment option for late/end mCRPC patients. Tandem approaches with [225Ac]Ac-PSMA may help expand understanding of how to optimize outcomes after [¹⁷⁷Lu]Lu-PSMA progression. However, these findings require confirmation in prospective, randomized studies comparing different rechallenge strategies to define optimal sequencing and patient selection criteria in advanced prostate cancer.