Correlating Ki67 and other prognostic markers with Oncotype DX recurrence score in early breast cancer
Background: Breast cancer is a common problem. Decisions regarding adjuvant chemotherapy are complex. Ki67 is increasingly used, in conjunction with conventional prognostic markers, to help decide the use of adjuvant chemotherapy for early breast cancer. Ki67 may be an economical alternative to Oncotype DX recurrence score (RS), which is a validated prognostic marker for disease recurrence and predictive marker for response to chemotherapy.
Methods: All known cases (n=33) of Oncotype DX performed for early breast cancer (T1-2, N0-1mi, M0, ER positive, HER2 negative) at an Australian tertiary private hospital from 14th December 2006 to 30th May 2012 were analysed. RS was correlated with Ki67, along with other conventional prognostic markers including tumour size, grade, mitotic rate and lymphovascular invasion. Spearman’s rank order correlation coefficient and Pearson product-moment correlation coefficient (r) were used for ordinal and continuous variables respectively.
Results: The median Ki67 was 12 (range 2-50), the median RS was 19 (range 3-65). There was no positive correlation between Ki67 and RS (r=-0.17, P=0.344). No single conventional prognostic marker was shown to significantly correlate with RS, including tumour size (r=-0.218, P=0.222), grade (r=0.253, P=0.155), mitotic rate (r=-0.18, P=0.921) and lymphovascular invasion (r=-0.147, P=0.415).
Conclusion: Ki67 and conventional prognostic markers do not correlate with Oncotype DX recurrence score. In the setting where conventional prognostic markers do not show a clear indication for adjuvant chemotherapy, Ki67 is not a substitute for Oncotype DX testing.
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