The Treatment Outcomes of Oligometastatic Colorectal Cancer Patients Treated with Stereotactic Body Radiation Therapy: A Multi-Institutional Analysis TROD 02-008

Abstract

<h3>Purpose/Objective(s)</h3> Stereotactic body radiotherapy (SBRT) is increasingly being used to treat oligometastatic cancers, but high-level evidence to support policy decisions is lacking in patients with colorectal carcinoma (CRC). The purpose of this study was to determine the prognostic factors for survival in oligometastatic colorectal cancer patients treated with SBRT in a multicentric setting. <h3>Materials/Methods</h3> The clinical data of 437 oligometastatic CRC patients who received metastasis directed treatment (MDT) via SBRT at 18 institutions between February 2007 and February 2021 were reviewed retrospectively. Patients either had de novo oligometastasis (≤5 metastases) at the time of diagnosis or had oligometastatic recurrences during follow-up. All patients were treated with the goal of curing their metastasis, and 839 lesions were irradiated. <h3>Results</h3> The average age was 61 years (range; 27-92 years). The majority of patients (58.8%) had colon carcinoma with a single organ metastasis (88.8 %). The average number of metastatic lesions was 2 (range, 1-5). There were 103 patients with liver metastasis, 222 patients with lung metastasis, 58 patients with lymph node metastasis, 60 patients with bone metastasis, 32 patients with brain metastasis, and 6 patients with other organ metastasis. Before RT, the median CEA and Ca-19-9 levels were 5.16 ng/mL (range: 0-8181.1 ng/mL) and 19.4 (range: 0.60 - 3693), respectively. After RT, the median CEA and Ca-19-9 were 5.00 ng/mL (range, 0.4-5693v ng/mL) and 18 (range, 0 - 6577), respectively. The average period of follow-up was 15.2 months (range, 0.3-91.5 months). The rates of OS and PFS after two years were 76.3 % and 28.1 %, respectively. Age (p<0.001), pre-RT CEA (p=0.006), pre-RT Ca19-9 (p=0.02), post-RT CEA (p=0.01), and post-RT Ca19-9 (p=0.02) were all significant prognostic factors for OS in univariate analysis. Age (HR=1.03, 95 % CI, 1.01-1.04, p=0.004) and pre-RT CEA (HR=1.01, 95 % CI, 1.00-1.02, p=0.04) were independent predictors of OS in multivariate analysis, while post-RT CEA (HR=1.93, 95 % CI, 1.28-2.90, p=0.002) was an independent predictor of PFS. <h3>Conclusion</h3> SBRT to oligometastatic lesions was found to be a safe and effective treatment modality for patients with colorectal cancer. Survival was predicted by age, baseline CEA, and the Ca19-9 response to MDT. Additional prospective studies with larger cohorts are necessary to validate our findings.