Correlating Ki67 and other prognostic markers with Oncotype DX recurrence score in early estrogen receptor-positive breast cancer

AimDecisions regarding adjuvant chemotherapy for early breast cancer 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 has been proposed as an economical alternative to Oncotype DX recurrence score (RS), which is a validated prognostic marker for disease recurrence and predictive marker for benefit from chemotherapy. This study aimed to determine in patients where conventional prognostic markers did not provide a clear recommendation for adjuvant chemotherapy, whether Ki67 could be a substitute for RS. MethodsWe reviewed all cases of luminal-type node-negative early breast cancer (T1-2, N0-1mi, M0, estrogen receptor positive, HER2 negative) referred for Oncotype DX testing by the multidisciplinary team at an Australian tertiary private hospital from 14th December 2006 to 31st December 2013, when conventional prognostic markers did not provide a clear recommendation for adjuvant chemotherapy. RS was correlated with Ki67, along with other conventional prognostic markers including tumor 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. ResultsA total of 58 patients were analyzed, median Ki67 was 15% (range 2-50%) and the median RS was 16 (range 3-65). There was no positive correlation between Ki67 and RS (r=0.01, P=0.93). No single conventional prognostic marker was shown to significantly correlate with RS, including tumor size (r=-0.02, P=0.88), grade (r=0.10, P=0.44), mitotic rate (r=-0.07, P=0.69) and lymphovascular invasion (r=-0.12, P=0.39). ConclusionKi67 and conventional prognostic markers do not correlate with Oncotype DX RS. In the setting where conventional prognostic markers do not show a clear indication for or against adjuvant chemotherapy as determined by consensus in a multidisciplinary team, Ki67 is not a substitute for Oncotype DX testing. RS may provide additional information to aid decision making for adjuvant chemotherapy.