Background: Radiation oncology practices and health plans typically engage in fee for service (FFS) contractual relationships, which employ utilization management techniques to manage treatment accordance with recognized guidelines. FFS contracts often result in unpredictable revenue streams for practices and burdensome administrative processes for both practices and payers. Moreover, there are limited mechanisms in FFS arrangements for practices and payers to systematically measure quality. Radiation oncologists and health plans share the common goal of systematically improving quality of patient care while reducing administrative burden. Methods: In 2012, Humana collaborated with a large national radiation therapy provider to implement ‘bundled’ case rate reimbursement instead of FFS. The case rate model was developed with HealthHelp, a radiation oncology quality vendor, and the payments were developed in the context of the appropriate modality for each cancer type. Changes in practice patterns were measured in the Medicare population by average fraction ratios across breast cancer, bone metastases, and prostate cancer. Fraction ratios compare delivered fractions to standards established by the National Comprehensive Cancer Care Network guidelines. A ratio of 1.0 means that the delivered amount met the recommended guideline. Ratios nearer to one (over or under) demonstrate appropriate therapy. Ratios were compared for 2011 vs. 2013 using T-tests. Results: Conversion from a FFS to case rate reimbursement did not coincide with a change in fraction ratios for breast cancer treatment. Fraction ratios for both bone metastases and prostate cancer moved towards the target ratio of 1.0 after the move to case rate reimbursement. Conclusions: After the implementation of case rate reimbursement, fraction ratios improved for bone metastases and prostate cancer, while breast cancer fraction ratios did not change. Future work will evaluate additional markers of quality and practice efficiency measurements.