Stereotactic ablative radiotherapy for oligoprogressive solid tumours: A systematic review and meta-analysis

Introduction: The aim of this systematic review and meta-analysis was to review evidence and pool outcomes to assess the effectiveness of stereotactic ablative radiotherapy (SABR) in patients treated for oligoprogressive metastases. Methods and Materials: A search was conducted January 2010 to January 2023 in five bibliographic databases for studies of patients with oligoprogressive disease treated with SABR to all lesions. Clinical outcomes included PFS (progression-free survival), OS (overall survival) and CST (change in systemic therapy). Descriptive statistics were used to summarize the data. Binary random effects model was used for pooled analyses. Results: 12,366 titles/abstracts screened, of which 25 met eligibility criteria and were included the review. All studies were published after 2017 with approximately 80% of the publications in 2021 and 2022. The primary tumour was prostate (n=8, 32%), kidney (n=6, 24%), colorectal (n=4, 16%) followed by breast (n=3, 12%), lung (n=2, 8%) and mixed (n=3, 12%). At 1 year, the pooled PFS was 44% (95% confidence interval [CI]: 34–53%, I²=91%); 53% (95% CI: 45–60%, I²=46%) in prostate, 49% (95% CI: 33–65%, I²=88%) in kidney, 62% (95% CI: 11–113%, I²=96%) in lung, 13% (95% CI: 3–24%, I²=39%) in breast and 30% (95% CI: 19–41%, I²=59%) in mixed. Discussion: There has been a surge in publications describing the use of SABR in oligoprogressive tumours. Published studies are mostly retrospective reported in prostate and kidney cancers, with limited evidence in other sites. Universal guidelines are recommended to ensure consistency in reporting and comparability of future studies.