59 Are Choosing Wisely Guidelines Applicable to Patients With a High Ki-67 Proliferation Index and Magee Equation Score?

59 Are Choosing Wisely Guidelines Applicable to Patients With a High Ki-67 Proliferation Index and Magee Equation Score?

Background

Choosing Wisely guidelines discourage routine axillary staging in older women with early-stage hormone receptor–positive/HER2-negative (HR+/HER2–), clinically node-negative (cN0) breast cancer. This study aimed to determine if sentinel lymph node biopsy (SLNB) can be safely omitted in such patients with guidance of the Ki-67 index and Magee Equation (ME) score.

Materials and Methods

Patients diagnosed with early-stage (tumor<5 cm), HR+/HER2–, and cN0 breast cancer from January 2010 to December 2012 were retrospectively identified from a prospectively maintained single-institution registry. Patients with bilateral breast cancer, distant metastases, clinically suspicious lymph nodes, and receipt of axillary lymph node dissection were excluded. Variables included age, race, tumor size, Nottingham score, nuclear grade, HR H-scores, Ki-67 percentage, clinical T stage, type of surgery, number and pathologic status of nodes retrieved, ME result, recurrence, and follow-up time.

Low, intermediate, and high Ki-67 indices were defined as 0% to 15%, 16% to 30%, and 31% to 100%, respectively. ME utilizes the Nottingham score, HR H-scores, tumor size, and Ki-67 percentage to estimate the Oncotype DX Recurrence Score. ME result was defined as either low (≤25) or high (>25). Primary end point was recurrence-free survival (RFS) at 5 years. Secondary end points were locoregional recurrence-free survival (LRFS) and overall survival (OS).

Results

Of 538 patients who met inclusion criteria, 435 (79%) underwent sentinel lymph node biopsy (SLNB). Median follow-up time was 6.1 years. Ki-67 index was low, intermediate, high, and unknown in 312 (58%), 138 (26%), 76 (14%), and 12 (2%) patients, respectively. ME was low, high, and unknown in 415 (77%), 42 (8%), and 81 (15%) patients, respectively. In multivariable analysis adjusting for clinical T stage, nuclear grade, and HR H-scores, neither the Ki-67 index (P = .65) or ME score (P = .45) were associated with a difference in relapse-free survival (RFS), local recurrence-free survival (LRFS), or overall survival (OS). In patients who had both an elevated Ki-67 index or ME, no patient had a nodal burden greater than 2 positive nodes. In patients who did not undergo SLNB, Ki-67 index and ME score were not associated with differences in outcomes.

Conclusion

In this study, patients with early-stage HR+, cN0 breast cancer with an elevated Ki-67 index and ME score, a surrogate marker of increased genomic risk, were not at risk for worse outcomes, including RFS, LRFS, or OS. These results suggest that SLNB can be safely omitted in this population even when a patient has high Ki-67 indices or ME, as the lack of this pathological nodal information does not affect the postoperative treatment plan.