OBJECTIVES: Medicare contracting reform resulted in the replacement of Medicare Part A/B claims processors, known as fiscal intermediaries (FIs) and carriers, with Medicare Administrative Contractors (MACs). This study examines the implementation of MACs on the receipt of chemotherapy and biologic agents for the treatment of metastatic colon cancer (mCC). METHODS: This retrospective study used Surveillance, Epidemiology and End Results (SEER) Medicare data to examine the receipt of National Comprehensive Cancer Network (NCCN) approved chemotherapy and biologic agents by elderly patients with mCC who were diagnosed between 2006 and 2009 and followed through 2011. The odds ratios associated with the interaction between pre/post MAC implementation and whether the implemented MAC had previously been a FI/carrier in the region were estimated using a generalized linear mixed model with a random effect for SEER-region.  Age, race, marital status, gender, Medicaid buy-in, poor-performance status, the Charlson Comorbidity Index and year of diagnosis were covariates in the model. RESULTS: The final sample included 9,509 patients.  4,034 (41%) received NCCN-approved chemotherapy at any time after diagnosis and 2202 (22%) received an NCCN-approved biologic at any time after diagnosis.  Individuals diagnosed post-implementation in a region where the MAC was not previously a FI/carrier had no reduction in the odds of receiving either NCCN-approved chemotherapy (odds ratio [OR]: 0.95, 95% confidence interval [CI]: 0.69–1.29) or NCCN-approved biologics (OR: 1.17, 95% CI: 0.85–1.61) at any time after cancer diagnosis as compared with patients diagnosed in the post period where the MAC was previously a FI/carrier.   CONCLUSIONS: Evidence was not found to support the hypothesis that MAC implementation impacted the odds of a Medicare mCC patient receiving NCCN-approved chemotherapy or biologic agents.  Future research should focus on examining the impact of Medicare contracting reform on specific treatment lines in combination with biologic use.