Background: Genomic tests provide critical information regarding risk of recurrence and inform treatment plans by identifying those patients who may safely forgo chemotherapy (CT) or shorten endocrine therapy (ET) duration. The IMPACT trial demonstrated that the 70 -gene risk of recurrence assay MammaPrint (MP) and 80-gene subtyping assay BluePrint (BP) inform treatment planning and increase physician confidence. However, not all genomic tests yield the same results. To examine consistency among genomic tests, we analyzed therapy implications for patients who received results from both MP/BP and Recurrence Score (RS). Methods: Using the FLEX cohort (NCT03053193), we examined 723 patients who received both MP/BP, and RS genomic assays. We assessed the potential clinical impact by examining the standardized reports of RS and MP/BP results. MP classified tumors as either ultralow, low, or high risk and BP further classified them as luminal, basal, or HER2. RS classified tumors as low (RS0-10), intermediate (RS11-25), or high (RS26-100). Clinical impact was defined as discordant genomic resulting in different treatment recommendations. Undertreatment indicates patients who may not have received CT based on RS but may have based on MP/BP and overtreatment those patients who would have received CT based on RS, but not based on MP/BP. ET duration too long is indicative of those patients that are ultralow risk by MP, regardless of RS classification, as those patients may have safely reduced the duration of their ET. Although outcomes are not available, treatment impacts are presuming a patient received both tests, but the treating physician opted to guide therapy according to the RS results rather than MP/BP. Results: We observed discordant results with a clinical impact in 49% (354) of patients, with 34% (244) who may be undertreated, 2% (11) potentially overtreated, and 14% (99) who may not be given the option to decrease ET to two years based on ultralow MP genomic risk. Of 114 concordant High-Risk tumors, 14% (16) were genomically Basal, and likely to require more aggressive CT than typically used in ER+ cancers. The table below summarizes the results. Conclusions: More than half of the patients in this cohort were at potential risk for undertreatment or overtreatment. The risk to patients is far more significant in the event of undertreatment, as this may result in incurable metastatic recurrence. Discordance between RS and MP/BP most often results in potential undertreatment if RS is used for treatment decision-making. Clinical trial information: NCT03053193.