BACKGROUNDThere are many treatment options for metastatic colorectal cancer (CRC). However, to the authors' knowledge, national treatment patterns for metastatic CRC, and the stability of hospital treatment patterns over time, have not been well described. METHODSData from the 2006 through 2011 National Cancer Data Base were used to study adults with newly diagnosed metastatic CRC (84,161 patients from 1051 hospitals). Using hierarchical models, the authors characterized hospital volume in the use of different treatment modalities (primary site resection, metastatic site resection, chemotherapy, and palliative care). The authors then assessed variation in the receipt of treatment according to the hospitals' relative volume of services used. Finally, the extent to which hospital treatment patterns changed over the past decade was examined. RESULTSOverall use of volume of services varied widely (5.0% in the hospitals with low volumes of service to 22.3% in the hospitals with high volumes of service). As hospitals' volumes of services increased, adjusted rates of metastatic site surgery (6.6% to 30.8%; P<.001) and multiagent chemotherapy (37.8% to 57.4%; P<.001) use increased, but primary site resection demonstrated little variation (56.8% vs 59.5%; P=.024). It is interesting to note that use of palliative care also increased (8.1% to 11.3%; P=.002). Hospital treatment patterns did not change over time, with hospitals with high volumes of service consistently using more metastatic site resection and multiagent chemotherapy than hospitals with low volumes of service. CONCLUSIONSThere is wide variation in hospital treatment patterns for patients with metastatic CRC, and these patterns have been stable over time. It appears that much of the approach for metastatic CRC treatment depends on the hospital in which the patient presents. Cancer 2015;121:1755-1761. (c) 2015 American Cancer Society. Wide variation in hospital treatment patterns for patients with metastatic colorectal cancer has been stable over time. It appears that much of the approach for the treatment of metastatic colorectal cancer depends on the hospital in which the patient presents.