Significance of Ki-67 Expression and Risk Category (St. Gallen 2007) in Elderly Breast Cancer Patients, with Emphasis on the Need for Postoperative Adjuvant Therapy

Breast cancer is increasing in the elderly. Although elderly breast cancer patients frequently receive less invasive therapy, its appropriateness is debatable. Ki-67 expression is a controversial prognostic factor and predictor of the efficacy of postoperative adjuvant therapy. This study investigated the value of the Ki-67 labeling index (LI) in elderly breast cancer patients, especially with respect to adjuvant therapy. This retrospective study investigated 82 primary breast cancer patients aged ≥ 70 years who underwent surgery between 1995 and 2005. Their clinicopathological findings were reviewed and their Ki-67 LIs were determined. The patients' mean age was 78 years, the mean observation period was 53.8 months, and 60 patients (73.2%) underwent adjuvant therapy. The St. Gallen (2007) risk category and the Ki-67 LI (mean, 15.3%) were both significantly correlated with relapse and prognosis. In the 31 cases with a low Ki-67 LI (< 10%), 1 patient who underwent adjuvant treatment relapsed, but there were no deaths. Among the intermediate- and high-risk patients, Ki-67 was low in 15; 1 patient who underwent adjuvant treatment relapsed, but there were no deaths. For elderly breast cancer patients aged ≥ 70 years categorized low risk by St. Gallen (2007) or with a low Ki-67 LI, the risk of relapse and death appears to be low regardless of adjuvant therapy. Though further investigation is needed to determine a method of measuring the Ki-67 LI and determining a cut-off value, our findings suggest that the Ki-67 LI helps with the selection of adjuvant therapy in elderly patients.