***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background Stereotactic body radiation therapy ( SBRT ) is an emerging treatment option for liver tumors . This study evaluated outcomes after SBRT to identify prognostic variables and to develop a novel scoring system predictive of survival . Methods The medical records of 52 patients with a total of 85 liver lesions treated with SBRT from 2003 to 2010 were retrospectively review ed . Twenty-four patients had 1 lesion ; 27 had 2 or more . Thirteen lesions were primary tumors ; 72 were metastases . Fiducials were placed in all patients prior to SBRT . The median prescribed dose was 30 Gy ( range , 16 – 50 Gy ) in a median of 3 fractions ( range , 1–5 ) . Results With median follow-up of 11.3 months , median overall survival ( OS ) was 12.5 months , and 1 year OS was 50.8 % . In 42 patients with radiographic follow up , 1 year local control was 74.8 % . On univariate analysis , number of lesions ( p = 0.0243 ) and active extralesional disease ( p < 0.0001 ) were predictive of OS ; Karnofsky Performance Status ( KPS ) approached statistical significance ( p = 0.0606 ) . A scoring system for predicting survival was developed by allocating 1 point for each of the three following factors : active extralesional disease , 2 or more lesions , and KPS ≤ 80 % . Score was associated with OS ( p < 0.0001 ) . For scores of 0 , 1 , 2 and 3 , median survival intervals were 34 , 12.5 , 7.6 , and 2.8 months , respectively . Conclusions SBRT offers a safe and feasible treatment option for liver tumors . A prognostic scoring system based on the number of liver lesions , activity of extralesional disease , and KPS predicts survival  following SBRT and can be used as a guide for prospect i ve validation and ultimately for treatment decision-making 
    Output:
    
CONCLUSION SBRT for liver oligometastases is an effective option for patients with advanced CRC , with encouraging local control and survival .