Genomic testing for breast cancer has become a common practice. The two main tests at our institution are Oncotype DX® and MammaPrint®. Each test has unique features and criteria. We sought to compare the practice pattern between these tests and compare them to patients who did not undergo any genomic testing. Methods: This is a retrospective review of all breast cancer patients between May 2008 and August 2011. Data was primarily thorough our tumor registry database. In some cases individual charts were also reviewed. Results: We analyzed 1093 breast cancers in 1064 patients. The average age was 62. The stage at diagnosis was 19% DCIS, 41% stage I, 24% stage II, 11% stage III and 5% stage IV. Of the 1093 cancers, 70 (6%) had an Oncotype test performed, 180 (16%) had a MammaPrint test done, 4 (0.4%) had both test, and 839 (77%) had no genomic test performed. Patients with an Oncotype test were more likely to be stage I than those with a MammaPrint (66% vs 48%). Additionally, patients who had a MammaPrint test more often received chemotherapy when compared to either the Oncotype test or no genomic testing. With a mean follow-up of 1.5 years, there have been 28 recurrences (0 in the Oncotype group, 5 in the MammaPrint group, and 23 in the no genomic testing group). All five of the MammaPrint recurrences were high risk and received adjuvant chemotherapy. Of the 23 recurrences in the no genomic testing group, eight patients were node negative and could have been considered appropriate for genomic testing, 6 of these eight did not have adjuvant chemotherapy. Conclusions: There are distinct practice pattern differences between Oncotype DX® and MammaPrint® utilization. MammaPrint testing was ordered more often in higher staged patients and was associated with an increased use of chemotherapy. This may relate to MammaPrint's previous requirement for fresh tissue that typically occurs before the final nodal status is known. This difference should diminish with the recent availability of MammaPrint on FFPE tissue. All patients who underwent genomic testing and developed a recurrence had been treated with adjuvant chemotherapy. In contrast, patients who did not have a genomic test and experienced a recurrence may have benefited from genomic testing. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P2-06-04.