Abstract
PURPOSE: Beta-blockers, originally developed for cardiovascular conditions, have been explored for their potential role in cancer treatment. Propranolol, a non-selective beta-blocker, has shown promise in inhibiting stress-induced signalling pathways associated with cancer progression. This systematic review aims to assess the evidence for the repurposing of propranolol as a treatment for various cancers, particularly breast cancer to answer the research question: Does propranolol improve cancer outcomes, including survival and recurrence? METHODS: We conducted a systematic search of MEDLINE, EMBASE, Global Health, Web of Science, and the Cochrane Library, including studies up to July 2024. Randomised Controlled Trials (RCTs), systematic reviews, and meta-analyses were included if they assessed the effects of propranolol on cancer outcomes such as mortality, survival, recurrence, or biomarkers of tumour regression. A narrative synthesis was performed to summarise the findings. RESULTS: Thirty-one studies were included, consisting of 7 RCTs, 4 systematic reviews and 20 meta-analyses. The evidence suggests that propranolol may improve cancer outcomes, especially when administered perioperatively, by reducing recurrence risk. However, the results remain inconclusive regarding its use in combination with chemotherapy or radiotherapy, as studies showed mixed results. The timing of propranolol administration, alongside its combination with other cancer therapies, appears to be a key factor in its effectiveness. CONCLUSION: Propranolol has potential as an adjunctive therapy in cancer treatment, particularly in reducing recurrence risk during the perioperative period. However, further clinical trials are needed to better define its role in cancer therapy, particularly regarding optimal treatment regimens and patient populations.