Comparison of SBRT for Oligometastatic Colorectal Cancer by Site: Lung vs. Liver.

Abstract

PURPOSE/OBJECTIVE(S)\nWe seek to report patient outcomes following Stereotactic Body Radiotherapy (SBRT) to the lung and liver for oligometastatic colorectal cancer (oCRC), and identify differences by tumor site and KRAS status.\n\n\nMATERIALS/METHODS\nAn IRB-approved prospective registry of 2138 lung SBRT patients and 294 liver SBRT patients was surveyed for patients with oCRC (defined as ≤ 5 lesions) involving the lung or liver treated with SBRT from 2005 to 2020. Patient, tumor, and treatment factors were analyzed. Actuarial rates for local control (LC), first local, regional or distant failure (TTFF), and overall survival (OS) were evaluated. Univariate analysis of outcome by KRAS status was conducted.\n\n\nRESULTS\n86 patients met study criteria, with 61 having lung, 24 patients having liver, and 1 patient having lung and liver SBRT. Median follow up was 24.8 months. Median age was 65.9 years (range 36.4 - 89.7), 63.9 for lung and 72.5 for liver (P\u202f=\u202f0.022). 56.3% of patients were male, 48.4% for lung and 76% for liver (P\u202f=\u202f0.018). Median KPS was 90 (range 70 - 100). 21.0% of lung patients had prior metastasis-directed therapy (MDT) (wedge resection, lobectomy). 60.0% of liver patients had prior MDT (surgery, bland embolization, RFA, Y-90). Mean liver lesion size (2.92 cm) was larger than mean lung lesion size (1.69 cm) (P < 0.0001). SBRT dose was 30 - 60 Gy in 1 - 8 Fx, with median dose of 50 Gy in 5 Fx for both lung and liver. 36% of patients were treated to 2+ synchronous lesions. 14% of patients had further SBRT to metachronous lesions. KRAS status was known for 71.3% of patients, 67.8% for lung, 80% for liver. Of those, KRAS mutation was present in 48.4% of patients, 47.6% for lung and 50% for liver. LC at 1 and 2 years was 87.9% (95% CI: 80.4 - 95.3) and 78.0% (95% CI: 68.1 - 88.0), respectively. OS at 1 and 2 years was 88.3% (95% CI: 81.5 - 95.1) and 74.1% (95% CI: 64.6 - 83.7), respectively. Median OS for all patients was 51.5 months, 59.0 months for lung and 19.5 months for liver (P < 0.0001). There was a statistically significant difference on log rank test between the lung and liver cohorts in both local control (P\u202f=\u202f0.008) and overall survival (P < 0.0001), see table. Median TTFF was 12.4 months for all patients, 14.3 months for lung and 5.1 months for liver patients (P\u202f=\u202f.690). There were no differences in LC or OS by KRAS status across all patients (P\u202f=\u202f.124 and P\u202f=\u202f.923 respectively), or for lung SBRT (P\u202f=\u202f.811 and P\u202f=\u202f.455 respectively), or liver SBRT (P\u202f=\u202f.167 and P\u202f=\u202f.247, respectively).\n\n\nCONCLUSION\nLocal control and overall survival with SBRT for oCRC were inferior in the liver compared to lung, likely due to larger lesion size, more extensive prior therapy, and more advanced age in the liver cohort. There were no differences in outcomes by KRAS status.