OBJECTIVES: Monitoring disease status and treatment planning for mCRC is contingent upon CT scan findings. Yet, due to limitations of case identification in the claims data, the frequency of CT scan in patients with mCRC in the real world setting and its impact on treatment duration is unknown. We devised a method to explored the utilization of CT scan and treatment pattern among mCRC patients who received National Comprehensive Cancer Network (NCCN) recommended first-line chemotherapies in combination with bevacizumab. METHODS: The De-identified Clinformatics® Data Mart (OptumInsight, Eden Prairie, MN) covering January 2008 to December 2016 was used for this exploratory analysis. Patients with mCRC and at least 180-day continuous insurance enrollment were identified using ICD codes. Receients of FOLFOX or FOLFIRI +bevacizumab were identified using HCPCS codes and the data of their 1^st treatment was registered as index date. SAS® software were used for data processing and analysis. RESULTS: A total of 1,120 colorectal cancer patients in the 1% sample of the OPTUM enrollees were captured and 32 of them received predefined treatments. Among the identified patients, 24 were FOFLOX recipients and 8 firstly received FOLFIRI; 68.75% were male; the median and mean age were 67.5 (41-84) and 66. The median and mean treatment duration were 153 (12-308 ) and 134.5 days respectively. 46.9% of the patients switched between the two therapies under study. The mean total CT scan frequency is 2.59 (1-9). The mean CT scan frequency per cycle (14 days) is 0.27 (0.08-0.75). CONCLUSIONS: The patient population and treatment patterns conform to the previously described treatment patterns in US and thus a valid dataset for exploring frequency of CT scan. We are accessing the 100% sample of OPTUM claims and will apply a regression model to estimate the association between CT scan frequency and treatment duration.