OBJECTIVES: To evaluate health care costs incurred by CRC patients post metastases  METHODS: Adult patients with a CRC diagnosis between January 1, 2005 and May 31, 2010 were identified from the Impact Intelligence Oncology Management (IIOM) registry. Patients with stage 4 CRC at diagnosis or development of metastasis were included. Registry data included original stage and date of diagnosis. Linked health care claims from a large US health insurance database affiliated with OptumInsight were used to identify health care costs and patient characteristics. To account for survival, Lin’s regression of total 4-year health care costs was conducted comparing stage and controlling for patient characteristics. Variable follow-up ended at earliest of death, disenrollment from health plan, or study end (11/30/10). RESULTS: A total of 598 patients, followed for an average of 653 days after first evidence of metastases, were included. At original study diagnosis, 310 patients were stage 4, 197 were unknown stage, and 91 stage 0-3. Mean unadjusted total cost was $252,200; outpatient hospital visits (excluding radiation, surgery) comprised the bulk of that, at a mean cost of $71,334. Hospitalization costs, with or without surgery (mean, $56,862), accounted for 33% of unadjusted mean total medical cost ($176,135). Outpatient office visits, chemotherapy, and biologics were also costly (mean, $36,217, $31,112, $38,276, respectively). On Lin’s regression, mean predicted total 4-year costs were: $361,197 (stage 4), $267,728 (originally stage 3; p=0.014 vs stage 4), $319,146 (originally stage 0-2; p=0.514), and $351,833 (originally unknown stage; p=0.757). Looking at the entire IIOM population (n=1,298), patients with metastasis, either at index diagnosis or later, had significantly greater costs than patients whose CRC did not metastasize (difference: $138,326; p<0.001). CONCLUSIONS: Predicted 4-year costs were highest among patients who initially presented with stage 4 CRC, and lowest among patients who presented with stage 3 and developed metastatic disease.