Abstract P2-11-12: Validation of modified Magee equations for predicting the oncotype DX recurrence score: A cost-effective alternative for estimating the risk of distant recurrence in receptor positive/node negative breast cancer patients
Authors: Turner BM , Skinner K , Huston A , Schiffhauer L , Shayne M , Ling M , Zhang Z , Jackson M , Tang P , Hicks D 
Published: August 2014

INTRODUCTION: Oncotype DX (ODX) (Genomic Health, Redwood City, CA, USA) is a multigene quantitative reverse transcription-polymerase chain reaction-based assay used to estimate the risk of distant recurrence for ER-positive, node negative-breast cancer patients. The quoted list price for ODX is $4.175.00. ODX reports a recurrence score (RS) that is divided into low (&lt; 18), intermediate (18-30), and high risk (≥ 30). The ODX RS has been shown to be prognostic and predict chemotherapy benefit in receptor positive breast cancer patients. The RS most highly weights genes related to proliferation (including Ki-67), HER-2, ER and PR. Klein et al. have previously shown that standard histological variables, in combination with semiquantitative ER, PR, HER-2, and Ki-67 results, can provide information similar to that found in the ODX RS using equations derived by linear regression analysis (Magee equations). In the current study, we have used a modification of these equations to validate their use in a cohort of breast cancer cases that were sent for ODX from our institution. MATERIALS AND METHODS: 233 cases (2009-present) with available ODX RS's (208 of these with Ki-67 results) were obtained from the pathology files at the University of Rochester Medical Center (URMC), and the histopathologic variables were extracted from the reports. Estimated RS's (URMC RS) were calculated by averaging results from the three published Magee equations, with a modification of the H-score for ER and PR. We estimated the H-score by multiplying the average intensity of staining by the% positive tumor cells. URMC RS's were compared with their paired ODX RS’s. RESULTS: The table shows the correlation between the ODX RS and URMC RS. 100% of cases with a high URMC RS also had a high ODX RS. There were no two step discordant results between a URMC RS and an ODX RS. A URMC RS correlated with an ODX RS of high, intermediate, and low in 7/12 (58%), 48/79 (61%) and 97/117 (83%) cases, respectively. Most of the discordant cases involved the intermediate/low groups, and the higher RS's in the discordant pairs were consistently close to the lower end cutoff point.The URMC RS and ODX RS would have resulted in similar treatment in 100% of patients.

Comparison of ODX RS and URMC RS; n = number of cases (URMC median, URMC range) ODX RS ⇒URMC RS ⇓HIGHINTERMEDIATELOWHIGH7 (35,32-40)00INTERMEDIATE5 (25,22-28)48 (22,18-30)20 (20,18-27)LOW031 (15,9-18)97 (14,7-18)

CONCLUSION: The modified Magee equations provide similar information as the ODX RS using information already generated by many laboratories, and may be a more cost-effective alternative than ODX in identifying breast cancer patients who might benefit from chemotherapy, or be spared its potential toxicity. If the estimated RS is clearly high or low, it is predictive of the ODX RS with a high degree of certainty. In our population a potential cost of $556,875.00 might have been avoided using the estimated RS. The estimated RS should not be dramatically different from the ODX RS. If there is a significant difference, this should be thoroughly investigated before decisions on adjuvant therapy are made.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-11-12.