Abstract
BACKGROUND: There is growing evidence to support the hypothesis that radical treatment of pulmonary oligometastatic disease with stereotactic body radiation therapy (SBRT) can improve oncological outcomes. However, some reports suggest colorectal cancer (CRC) pulmonary metastases are associated with radioresistance. The present systematic review aimed to assess the local control (LC), overall survival (OS), and progression-free survival (PFS) of patients with CRC pulmonary metastases treated by SBRT. Secondary outcomes included assessment of peri-procedural complications and identification of prognostic factors on LC. METHODS: Electronic databases were systematically searched from their dates of inception using predefined criteria. Summative statistical analysis was performed for patients with CRC pulmonary metastases, and comparative meta-analysis was performed for patients with CRC versus non-CRC pulmonary metastases. RESULTS: Using predefined criteria, 18 relevant studies were identified from the existing literature. LC for CRC pulmonary metastases treated by SBRT at 1-, 2-, and 3-year were estimated to be 81%, 66%, and 60%, respectively. OS and PFS at 3-year were 52% and 13%, respectively. Patients with CRC pulmonary metastases were associated with significantly lower LC compared to non-CRC pulmonary metastases [HR, 2.93; 95% confidence interval (CI), 1.93-4.45; P<0.00001], but higher OS (HR, 0.61; 95% CI, 0.45-0.82; P=0.001). There were no reported periprocedural mortalities and low incidences of periprocedural morbidities. CONCLUSIONS: These findings may have implications for patient and treatment selection, dose fractionation, and support the hypothesis that CRC pulmonary metastases may require higher biological effective doses while respecting normal tissue constraints when treated with SBRT.