Prognostic factors and risk stratification for survival in oligometastatic colorectal cancer treated with stereotactic body radiotherapy.

Abstract

Purpose: This study aimed to evaluate treatment outcomes with associated prognostic factors, and to guide treatment strategies in colorectal cancer patients with oligometastatic disease (OMD) treated with stereotactic body radiotherapy (SBRT).

Materials and methods: This retrospective study included 74 colorectal cancer patients who received SBRT for 113 lesions (88 lung, 19 liver, and 6 lymph node). Each OMD was considered a separate case for patients repeatedly diagnosed with OMD. The log-rank test and Cox proportional hazards model were used to assess prognostic factors for progression-free survival (PFS).

Results: A total of 84 cases were analyzed. The median follow-up period was 32.2 months (range, 8.2 to 89.3 months). The 2-year PFS, widespread failure-free survival (WSFFS), and overall survival (OS) rates were 35.1%, 67.4%, and 80.8%, respectively. In the multivariable analysis, oligometastatic status (repeat/induced vs. de novo; hazard ratio [HR], 2.66; 95% confidence interval [CI], 1.40 to 5.04; p = 0.003) and planning target volume (PTV) volume (17.6 vs. <17.6 cm3; HR, 1.99; 95% CI, 1.09 to 3.62; p = 0.025) were significant prognostic factors for PFS. Cases with two risk factors for PFS demonstrated significantly worse OS and WSFFS (p < 0.05), whereas those with one risk factor did not show a significant difference compared to cases with no risk factors.

Conclusion: SBRT for oligometastatic colorectal cancer showed favorable clinical outcomes. Oligometastatic status and PTV volume were significantly associated with PFS. Risk stratification based on the number of poor prognostic factors of PFS may help guide treatment strategies for colorectal cancer patients with OMD.