Radiolabeled LHRH and FSH Analogues as Cancer Theranostic Agents: A Systematic Review.

G-protein-coupled receptors (GPCRs) play pivotal roles in tumor growth and progression. Among these, the luteinizing hormone-releasing hormone receptor (LHRH-R) and follicle-stimulating hormone receptor (FSH-R) represent promising translational targets, unlike luteinizing hormone receptors (LH-Rs). Indeed, both LHRH-R and FSH-R are selectively expressed in various cancers and their vasculature, offering opportunities for receptor-mediated imaging and therapy. This systematic review aims to evaluate radiolabeled LHRH- and FSH-derivative biomolecules, including peptides, monoclonal antibodies and nanocarriers, for their applications in cancer diagnosis and treatment. The systematic review was conducted following PRISMA 2020 guidelines. A systematic search of PubMed, Scopus and Web of Science was conducted for studies published between 2005 and 2025. A total of 248 records were identified, and 156 articles were screened after removing duplicate records. Two authors independently selected eligible studies. Quality of evidence was assessed by the (QUADAS) approach. A total of 25 studies met the inclusion criteria and were included in the final review. Radiolabeled LHRH and FSH derivatives showed receptor-specific tumor localization in both preclinical and clinical applications. FSH-R expression in tumor blood vessels supports its potential as a biomarker for early cancer diagnosis. FSHβ-derived peptides exhibit improved pharmacokinetics compared to monoclonal antibodies in PET imaging. LHRH analogues, particularly D-Lys-modified peptides, proved effective for SPECT, PET and therapeutic applications, particularly in breast and prostate cancer. The integration of radiolabeled LHRH and FSH derivatives with nanocarriers further enhanced probe stability and tumor targeting, increasing tumor accumulation and image contrast compared to free peptide. Radiopharmaceuticals targeting LHRH-R and FSH-R are promising tools for cancer imaging and treatment. Advances in nanotechnology enhance delivery precision and reduce systemic toxicity, thereby increasing its translational promise in oncology.