The gene expression profiling assay OncotypeDx (ODx) prognosticates the risk of estrogen receptor positive (ER+) breast cancer (BC) recurrence and assesses the likely benefit from adjuvant chemotherapy in addition to endocrine therapy. There have been several attempts to develop algorithms that provide similar outcome prediction to the ODx assay with the use of routine clinicopathological characteristics. Ki67 is frequently incorporated into these assessments, although there is no standard cut-off for its use.
We retrospectively reviewed the electronic medical records of 330 patients with early stage ER+ BC for whom ODx recurrence score (RS) was available. Patients were diagnosed and treated at two specialized cancer centers between 2014 and 2017. Our objective was to determine the ki67’s median differences between ODx risk groups. We used Spearman rho for the correlation between Ki67 and ODx score and used Kruskal-Wallis test for compare medians, pairwaise comparison for the intergroup relations.
Mean age at diagnosis was 57.42 years (range 28-89). Mean tumor diameter was 15.67 mm. 78.9% were intermediate histologic grade and 9.7% patients had lymph node involvement. Median expression of ER and PR were 90% (5-100) and 70% (0-100), respectively. We assessed the correlation between Ki67 and ODx score, with a pearson r:0.31, p < 0.001. The data showed a directly proportional trend between Ki67 and ODx score. Median Ki67 was 20 (1-100). According to ODX RS, 61.5% of tumors were low risk, 30.3% were intermediate risk and, 8.2% were high risk. Median Ki67 within each category group is as follows: low: 15 (IQR:15), intermediate: 20 (IQR:18) and high: 40 (IQR:35), with a statistically significant difference between medians (p < 0.001). In the Pairwise comparison intergroup the data showed: Low-Intermediate (p < 0.05), Low-High (p < 0.001), Intermediate-High (p < 0.001).
The data showed directly proportional trend between Ki67 and ODx score. In our population there is a statistically significant difference between Ki67 medians according to ODx risk groups.
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