Gene expression profiling testing is seen by patients and oncologists as a valuable aid in making decisions about whether or not to undergo chemotherapy. Many patients and oncologists rely heavily on the results (i.e., recurrence risk score) for treatment decision making. Patients expect tests to provide valid, personalized, individualized and authoritative results that determine the most appropriate course of treatment. While low and high risk results may meet these expectations, intermediate results defy them. Instead, people identified with intermediate risk face further confusion and anxiety in what is an already emotionally-laden decision. Oncologists use gene expression profiling testing for a range of purposes from communicating to patients, to reducing uncertainty and helping them feel more confident in their decisions for clinically indicated disease and beyond. Some oncologists expressed concern around overreliance on the results of gene expression profiling testing in treatment decision making, with inadequate consideration of other relevant clinical and pathological characteristics.Patients’ preferences for chemotherapy were viewed as critical to determining whether or not to proceed with gene expression profiling testing, as the value of testing is seen as contingent on its ability to be used in treatment decision making. While understanding patients’ preferences for and willingness to undergo chemotherapy were identified as critical to guide testing decisions, patients’ preferences were not used consistently by oncologists in deciding whether to order testing. Some patients did not understand the nature of testing and the possibility of it being fallible. Instead its certainty and validity was assumed through notions of testing being of a personalized and individual nature. Because of the need to communicate complex information about the nature and purpose of the test, elicit patients’ preferences for treatment, and make decisions based on the results, implementation of gene expression profiling testing would likely require additional time in terms of length and number of consultations with oncologists. Ordering the test at the appropriate time in care is important so as to avoid delays in testing and subsequent delays in treatment or by initiating unnecessary treatment.