Abstract P3-07-03: Magee Decision Algorithm™: A safe and effective method to make therapy decisions without oncotype DX® testing
Authors: Bhargava Rohit , Clark Beth Z , Carter Gloria J , Dabbs David J 
Published: March 2020

Background: Magee Equations™ are multi-variable models that can estimate oncotype DX® (ODX) score (Flanagan M, 2008. PMID: 18360352 and Klein ME, 2013. PMID: 23503643). One of the equations (Magee Equation 3) has been shown to predict for pathologic complete response to neoadjuvant chemotherapy in ER+/HER2-negative tumors (Farrugia DJ, 2017. PMID: 28548119).

We recently described a decision algorithm using Magee Equations and tumor mitotic activity score to safely forgo ODX testing (Bhargava R, 2019. PMID: 30395177).

Methods: The current study tests the accuracy of Magee Decision Algorithm (MDA) using a large in-house database. According to the algorithm, if all Magee Equation scores are &lt;18, or 18-25 with mitosis score of 1, then ODX testing is not required as the actual ODX recurrence score (RS) will be ≤25 (these cases were labeled as “do not send-expect low risk”). If all Magee equation scores are 31 or higher, then also ODX testing is not required as the actual score will be &gt;25 (labeled as “do not send-expect high risk”). All other cases could be considered for testing (labeled as “send’). We analyzed all ER+, HER2 negative cases (including HER2 IHC 2+ cases with HER2 copies of 4 to &lt;6) sent for ODX testing with available pathology parameters for calculation of all Magee Equations. A total of 1824 cases over 11 year period sent for clinical ODX testing formed the basis of this study.

Results: Of the 1824 cases, 1266 (69.4%) were classified as “do not send” and 558 (30.6%) as “send”. The classification accuracy in the “do not send” group was 94.6% (see table 1).

Table 1:Do not send-expect high riskDo not send-expect low riskTotalActual ODX RS &gt;25166783Actual ODX RS ≤25111821183Total1712491266Accuracy of “do not send”: 16+1182/1266 = 94.6%Ability to predict low-risk (≤25): 1182/1249= 94.6%Ability to predict high-risk (&gt;25): 16/17= 94.1%

We further examined the clinical outcome in 67 cases that were expected to show an ODX RS of ≤25 but the actual ODX RS came back as &gt;25. Of these 67 patients, 36 received chemo-endocrine therapy, 2 received chemotherapy only, 24 had endocrine therapy alone (mostly an aromatase inhibitor), and 5 did not receive any systemic therapy. The average follow up was 78 months. The follow up duration was similar for the chemo-endocrine therapy group (inter-quartile range of 57-100 months) and in the endocrine therapy alone group (interquartile range of 60-97 months). There were 3 distant recurrences, 2 in patients that received chemo-endocrine therapy and one in a patient who did not receive any systemic therapy. No distant recurrences were recorded in the group that received hormonal therapy alone. Two of the patients with recurrence died of disease (one patient who received chemo-endocrine therapy and other who did not receive any systemic therapy). There were 2 other deaths in the cohort but the cause was unrelated to breast cancer.

Conclusions: The MDA using Magee equations and mitosis score accurately identifies cases that will not benefit from ODX (or other similar) testing. Such cases constitute ~70% of the routine clinical ODX requests. If Magee algorithm is regularly used in routine practice, then it will save $300,000 per 100 test requests. The occasional discordant cases (expected ≤25, but actual ODX RS &gt;25) appears to have an excellent outcome on endocrine therapy alone.

Citation Format: Rohit Bhargava, Beth Z Clark, Gloria J Carter, David J Dabbs. Magee Decision Algorithm™: A safe and effective method to make therapy decisions without oncotype DX® testing [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-07-03.