ESTRO 2024 - Abstract Book

S1865

Clinical - Mixed sites, palliation

ESTRO 2024

Metastasis-directed therapy (MDT) with stereotactic body radiation therapy (SBRT) is emerging as an effective, novel, therapeutic option for oligometastatic disease (OMD). However, a lack of phase III data, consensus guidelines and concerns for severe toxicity limit its widespread use in certain clinical scenarios. Randomized controlled trials (RCTs) routinely report hazard ratios (HRs) which lack clear clinical interpretation as well as medians which provide only a local summary of survival. Restricted-mean survival time (RMST) is the duration of time a patient is expected to survive over the follow-up period, providing a robust alternative and clinically interpretable summary of survival. We analyzed the efficacy of SBRT in OMD using RMST.

Material/Methods:

All registered RCTs of local ablative radiotherapy in OMD in ClinicalTrials.gov through 2022 were identified. Patient level data were reconstructed from published Kaplan-Meier survival curves, and the HRs and RMST differences were estimated for surrogate endpoints (SEs) and overall survival (OS).

Results:

Five phase II and one phase III studies comprising 426 patients met the inclusion criteria. The most common primary disease site was lung cancer at 53.8% of patients, followed by prostate (31%), and breast or colorectal cancer (4.2% each). The MDT modality was radiotherapy in 94.5%, radiotherapy and surgery in 2.5%, and surgery alone in 2.9%. The RMST differences for SEs ranged from 4.6 months (95% CI 1.4-7.8) in a study by Iyengar et al. to 11.1 months (95% CI 5.0-17.2) in SABR-COMET. The RMST differences for OS in SABR-COMET, Gomez et al., and SINDAS studies were 12.6 (95% CI 2.6-22.7), 15 (95% CI 3.8-27) and 7.9 months (95% CI 4.1-11.6), respectively.