Abstract P3-09-08: Patterns of oncotype DX testing and adjuvant chemotherapy use in a tertiary care centre
Authors: Sudan Gautam , Mates Mihaela , Wilma Hopman 
Published: May 2015

Abstract
Introduction:
The Oncotype DX Recurrence Score (RS) is a 21-gene signature, retrospectively validated prognostic marker and predictor of response to adjuvant chemotherapy (ACT) in estrogen receptor (ER) positive breast cancer (BC). In 2010 RS became publicly funded in Ontario for patients with estrogen-positive, HER2 negative and node negative breast cancer. The aim of our study was to explore the pattern of RS testing and use of adjuvant chemotherapy at the Cancer Centre of Southeastern Ontario (CCSEO) since the introduction of RS testing. Additionally we compared the RS tested patients with a matched cohort treated for early BC prior to 2010.
Methods:
A retrospective paper and electronic chart review was undertaken of patients with early BC (stage 1 and 2) with the following pathologic features: T1-T2, N0/N1mic, ER positive and Her-2neu negative. We collected patient demographics, co-morbidities, surgical data, tumour characteristics, ACT use, Adjuvant! mortality estimates and breast cancer outcomes. Cohort A included patients who underwent RS testing (2010 – 2013) and cohort B patients treated prior to 2010. The two cohorts were compared using chi-square tests for categorical data, and independent samples t-tests and the Mann-Whitney U for continuous data.
Results:
160 patients were included in our analysis of which 83 underwent RS testing. Compared to cohort B, cohort A was older (median age 60 versus (vs) 48, p&lt;0.001); had higher postmenopausal status (77 vs 34%, p&lt;0.001); higher rates of breast conserving surgery (88 vs 74%, p=0.024) and sentinel node biopsy (94 vs 26%, p&lt;0.001). Cohort A also had larger tumors (T2 23 vs 5%, p=0.010), higher stage (stage 2 - 24 vs 6%, p=0.002) and higher Adjuvant! mortality estimates above 15% (18 vs 8%, p=0.054). Despite this the use of ACT decreased significantly (20 vs 98%, p&lt;0.001). The majority of patients received adjuvant endocrine treatment (&gt; 90% in both cohorts). Of the 83 patients in cohort A 55 (66%) had low risk RS (0-17), 18 (22%) intermediate risk (18-30) and 10 (12%) high risk RS. ACT was received by 2 of 55 patients with low RS; 6 of 18 patients with intermediate RS and 9 of 10 with high RS. Median follow-up was only 16 months in cohort A vs 74 months in cohort B. 92% of patients in cohort B remain recurrence free. To date only 2 patients in cohort A have recurred, both of which had high RS scores and received ACT.
Conclusion:
In patients with early BC undergoing RS testing at CCSEO we observed a higher proportion of low risk RS as compared to the literature. Additionally, despite larger tumors, higher stage disease and higher Adjuvant! mortality estimates above 15%, the proportion of patients undergoing ACT has significantly decreased since the introduction of RS testing. So far this has not translated into a negative long-term disease outcome although longer follow-up is needed for real-world validation.
Citation Format: Gautam Sudan, Mihaela Mates, Hopman Wilma. Patterns of oncotype DX testing and adjuvant chemotherapy use in a tertiary care centre [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P3-09-08.