Background or Purpose: To compare the cost-performance between planned short-course radiation and upfront concurrent chemoradiation on metastatic rectal cancer. Methods: A total of 75 patients with metastatic rectal cancer who underwent planned short-course radiation or upfront concurrent chemoradiation were enrolled. The Kaplan-Meier method was used to compute the survival rates. The χ2 test was used to compare baseline characteristics. The Cox proportional hazards model was applied to determine the prognostic influence of clinicopathological factors. Results: The planned short-course radiation is superior to upfront concurrent chemoradiation in overall survival for the patients with metastatic rectal cancer (34.8 vs. 20.2 months, P = 0.010). The planned short-course radiation was an independent prognostic factor (P = 0.009, HR (95% CI) = 0.319(0.135–0.752)). The efficacy of radiation on downstaging was similar between planned short-course radiation and upfront concurrent chemoradiation. The total cost of concurrent chemoradiation is 4.52-fold more expensive than that of short-course radiation (340,142 vs. 75,106 NT dollars, respectively). Conclusions: Based on the impressive cost-performance of planned short-course radiation compared with upfront concurrent chemoradiation (better OS, modest downstaging and lower cost), planned short-course radiation should be the preferred radiation approach for managing metastatic rectal cancer.