Abstract 149P
Background
Oncotype Dx recurrence score provides prognostic and predictive information for recurrence in early stage breast cancer. Patients with low oncotype Dx scores (=<25) are less likely to recur and often adjuvant chemotherapy is not necessary. However, a small minority of patients with low Oncotype Dx scores will experience recurrence. In this retrospective study, we examined whether high Ki67 could predict the distant recurrence in early stage breast cancer with low oncotype Dx scores.
Methods
This was a single center retrospective cohort study. Key inclusion criteria were: hormone receptor-positive, HER2 negative (T1-2 N0 M0) breast cancer diagnosed between 2008 and 2015 with a low oncotype Dx (=<25). Data cut-off was in December 2020 with a median follow-up of 7 years. Tumors that were >=15% + for Ki67 were considered “high Ki67” and those with less than 15% Ki67+ cells were classified as “low Ki67”. Fisher’s exact test was used to assess differences between Ki67 groups. Cox-regression models were used to assess differences in distant metastasis-free survival.
Results
We identified 278 consecutive patients with low Oncotype Dx scores. The median age at diagnosis was 60 (range 30 - 79), 274 patients were estrogen receptor (ER) >=90% and remaining 4 cases were ER 75-85%. 29 patients were low positive (=<10) for progesterone receptor (PR) and remaining 249 patients were PR high. 209 (75%) of tumors were <=2cm (T1) and 69 (25%) tumors were >2cm (T2). 271 (97%) patients received adjuvant anti-hormonal treatment for an average of 5 years (ranging from 6 months to 10 years). 148 (53%) patients were in Ki67-low and 130 (47%) were Ki67-high. Median oncotype Dx was 15 and 16 in low versus high-Ki67 groups. Of all cases in the study, 13 patients (4%) experienced distant metastasis. Recurrence rate was significantly higher in the Ki67-high group 9.2% (12/130) versus the Ki67-low group 0.7% (1/148) (P=0.001). Distant metastasis free survival was significantly shorter in patients with high vs. low Ki67 tumors (HR=12.7, 95%CI 1.7-98.2, P=0.014).
Conclusions
Among patients with low risk oncotype Dx, those with high Ki67 tumors are at higher risk of relapsing. Ki67 status may help to identify a subset of low risk Oncotype Dx patients who could benefit from adjuvant chemotherapy.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
A.A.N. Rose: Financial Interests, Personal, Advisory Board: Pfizer. All other authors have declared no conflicts of interest.