Assessing the Clinical Effectiveness of Radioimmunotherapy with Combined Radionuclide/Monoclonal Antibody Conjugates in Cancer Treatment: Insights from Randomised Clinical Trials

Background: Despite the development of advanced cancer therapies, achieving cancer eradication remains challenging. Radioimmunotherapy (RIT) is an innovative approach that combines radionuclides with monoclonal antibodies targeting tumour-associated antigens or those expressed by the tumour microenvironment. Over the past two decades, RIT has been extensively researched, along with two RIT products—90Y-ibritumomab tiuxetan and 131I-tositumomab. However, despite its demonstrated efficacy in non-solid tumours, RIT’s clinical use remains limited, and its effectiveness in solid tumours is inconclusive. This study aimed to analyse randomised controlled trials (RCTs) to evaluate the overall clinical effectiveness of RIT across different cancer types and its impact on treatment outcomes. Methods: A systematic search of PubMed, EMBASE, Scopus, CENTRAL, and Google Scholar was conducted from January 2000 to October 2024 in accordance with PRISMA guidelines and the PICOS framework. Studies were included if they were RCTs evaluating RIT for cancer treatment and reported treatment outcomes such as overall survival (OS), progression-free survival (PFS), disease-free survival, or time to progression (TTP). Data extraction was performed using a standardised Excel form, and study quality was assessed with the Joanna Briggs Institute Critical Appraisal Tool for RCTs. A narrative synthesis of the data was complemented by meta-analyses where feasible, particularly for progression- and survival-related endpoints. Results: Out of 2241 records identified, 20 RCTs encompassing approximately 3562 patients were included. The majority of trials focused on non-solid tumours, particularly non-Hodgkin’s lymphoma (NHL), while a smaller subset evaluated solid tumours such as lung, pancreatic, ovarian, and prostate cancers. Most non-solid tumour studies employed 90Y-ibritumomab tiuxetan or 131I-tositumomab, targeting the CD20 antigen, whereas limited evidence exists for RIT efficacy in solid tumours. Meta-analysis of progression-related outcomes yielded a pooled hazard ratio (HR) of 0.48 (95% CI: 0.39–0.59), indicating a 52% reduction in the risk of progression. In contrast, overall survival outcomes were more variable, with a pooled OS HR of 0.80 (95% CI: 0.60–1.07). Adverse events, predominantly haematological and nonhaematological toxicities, were common yet generally reversible. The findings suggest that RIT, especially when used as part of combination regimens, significantly improves treatment outcomes in non-solid tumours but has an inconsistent effect in solid tumour settings. Conclusions: The results underscore the clinical promise of RIT in treating non-solid tumours like NHL, where combination regimens yield superior outcomes compared to monotherapy. However, the inconclusive evidence in solid tumours highlights the need for further large-scale, well-designed RCTs to define the optimal use, dosing, and patient selection for RIT in these settings. Additionally, standardisation in outcome reporting and longer follow-up periods are essential for more accurate economic and clinical assessments. Overall, RIT represents a valuable therapeutic modality, yet its integration into cancer treatment regimens should be guided by further research aimed at mitigating toxicity and optimising combination strategies.