Multi-institutional analysis of extracranial oligometastatic colorectal cancer patients treated with stereotactic body radiation therapy: TROD 02-008 study.

Purpose: To investigate the treatment outcomes of extracranial oligometastatic colorectal cancer (CRC) patients treated with stereotactic body radiotherapy (SBRT).

Materials And Methods: The clinical data of 388 extra-cranial oligometastatic CRC (≤ 5 lesions) patients and 463 lesions treated with SBRT at 19 cancer institutions were retrospectively analyzed. The prognostic factors predicting overall survival (OS), progression-free survival (PFS), and local control (LC) were assessed in uni- and multivariable analyses.

Results: The median age was 62 years (range, 29-92 years). The majority of the patients (90.5%) received surgery and systemic treatment for their primary tumor, had ≤ 2 metastasis (83.3%), had single organ involvement (90.3%), and staged using flouro-deoxyglucose positron emission tomography (FDG-PET/CT) (76%). The median fraction and total radiation doses were 10 Gy (range: 6-34 Gy) and 50 Gy (range: 8-64 Gy), respectively, delivered in a median of 4 fractions (range: 1-8). The median follow-up time for the entire cohort was 30.7 months (interquartile range: 27.0-34.3 months). The 3‑year OS, PFS, and LC rates were 64.0%, 42.3%, and 72.7%, respectively. The 3‑year LC rate was significantly higher in patients receiving BED ≥ 100 Gy than those receiving BED < 100 Gy (76.0% vs. 67.3%; p = 0.04). The 3‑year PFS and OS rates were higher in patients receiving BED ≥ 100 Gy than those receiving BED < 100 Gy (33.2% vs. 25.2%; p = 0.03; 53.7% vs.  44.8%; p = 0.02). Single metastasis and complete response after SBRT were independent prognostic factors for survival in multivariable analysis.

Conclusions: In this multi-center study, we demonstrated that SBRT is an effective treatment option of metastatic lesions in oligometastatic CRC patients by providing promising LC rates. Higher SBRT doses beyond BED ≥ 100 Gy were associated with improved LC and survival. LC of treated lesion and lower tumor burden after SBRT were associated with better outcomes.