Experience with Use of the Oncotype DX Gene Assay Test in a Multicenter Community-Based Healthcare System.
Authors: Gregg X. , Belnap T. , Rowley B. , Rees W. 
Published: December 2010

Abstract
Background:Oncotype DX has been validated to quantify the risk of distant recurrence and predict the benefit of chemotherapy (CT) in ER positive, node negative breast cancer treated with tamoxifen. A retrospective study was undertaken to assess the use of the Oncotype DX test at Intermountain Healthcare. Intermountain is a not-for-profit healthcare system with 21 inpatient facilities, 9 comprehensive cancer centers and 42 affiliated medical oncologists ranging from single practitioners to multiphysician groups.Methods: This study contains a group of T1-3 N0 ER+ breast cancer patients who received an Oncotype DX test paired with a control group of non-tested T1-T3 N0 ER+ patients receiving hormone therapy (HT) from the same period. Data comes from a supplemental database containing treatment and follow-up data from individual physician offices combined with data from Intermountain's cancer registry. To ensure data completeness, Genomic Health provided a list of relevant Oncotype DX results for study patients. The analysis was done using multivariate logistic regression and controlled for age, tumor size, grade and T stage.Results: From 2005 to 2008, Oncotype DX testing was performed on tumor specimens from 285 patients. 8 patients had positive nodes and 4 patients were ER negative. In addition, 9 patients did not and will not receive HT (5 refused, 4 contraindicated) and 9 patients have yet to begin HT. 11 patients were lost to follow-up. Of the remaining 244 patients who form the study group, six patients were Her-2 neu positive (1 high recurrence score (RS), 3 intermediate and 2 low). Tumor size ranged from &lt;1 cm to 7 cm, but 80% were &lt;2 cm. 120 study patients (49%) had a low RS, 95 (39%) intermediate and 29 (12%) high. Only 2% of patients in the low RS group received CT, whereas 93% of patients in the high RS group and 40% in the intermediate RS group received CT.An analysis of potential factors affecting CT treatment decision making in the intermediate RS group showed that 60% of the 15 patients under age 50 received CT, compared to 36% of the 80 patients age 50 and over. CT was given in 35% of grade 1, 40% of grade 2 and 50% of grade 3 tumors. 43% of patients with a &lt;1 cm tumor received CT compared to 42% of 1-2 cm tumors and 28% of tumors &gt;2 cm. Compared to our control group of 688 patients, Oncotype DX-tested patients are younger (p&lt;0.01), less likely to have T1a (p=0.03), more likely to have T1c (p&lt;0.01) or T2 (p=0.03) tumors and less likely to undergo CT (p&lt;0.01). Low RS patients are less likely to receive CT (p&lt;0.01) and high RS patients more likely to receive CT (p&lt;0.01), whereas intermediate RS patients showed no significant difference (p=0.07) but were trending toward receiving less CT than the control group.Conclusions:Virtually all patients with a low RS received only HT, while most patients with a high RS also received CT. In patients with an intermediate RS, younger age and higher grade may impact clinicians' decisions to administer CT, while a larger tumor size does not. Overall, patients undergoing Oncotype DX testing are less likely to receive CT. These data indicate that the use of Oncotype DX testing facilitated appropriate therapeutic decisions in most patients.
Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6058.