P5-01-11: Small Node-Negative (T1b-cN0) Invasive Hormone Receptor (HR)-Positive Breast Cancers: Is There a Population Which Might Have Benefit from Adjuvant Chemotherapy?

Abstract

Abstract Background It has been widely accepted that small and node-negative breast cancers have an excellent prognosis and do not generally have clinical benefit from adjuvant chemotherapy. Recently, the role of adjuvant chemotherapy for small node negative breast cancers has been justified in some high-risk patients, which include HER2−positive and triple negative breast cancers. However, the question has been raised as to whether there are some patients who might have benefit from adjuvant chemotherapy in small node-negative HR-positive breast cancers. According to the current 2011 NCCN guideline, 21-gene RT-PCR assay can be considered for tumor size of more than 0.5 cm in HR-positive, HER2−negative cancers. In cases of high recurrence score (≥ 31), adjuvant chemotherapy in addition to endocrine therapy is recommended as category 2B. Because gene array cannot routinely be used in clinical practice and has not been validated in prospective randomized trials and the usefulness of it still needs to be defined, it would be better if there were valuable markers to determine risk for relapse in this setting. We hypothesized that there could be a population who might have clinical benefit from adjuvant chemotherapy in this small node-negative HR-positive tumors. Patients and Methods We retrospectively analyzed the clinicopathologic characteristics and outcomes of 538 postoperative HR-positive (ER-positive and/or PgR-positive) T1b-cN0 breast cancer patients between 2004 and 2007 at the Samsung Medical Center. We performed Cox regression multivariate analysis for relapse using variables from univariate analysis by log-rank test for relapse. Results: The median age at diagnosis was 46 years (range, 22–79). During the median 60.5 months of follow-up, the 5-year recurrence rate was 5.2%. Anthracycline-based adjuvant chemotherapy was administered to 44.8% of the patients. Adjuvant endocrine and radiation treatment were administered to 94.6% and 63.7% of the patients. There were significant differences according to histologic grade (HG), Ki67 index, and age of less than 35 years in univariate analyses regarding RFS (p=0.003, p<0.0001, and p=0.003, respectively by log-rank test). There was no significant difference according to tumor size of subcentimeter (< 1cm) (p=0.826). In Cox regression multivariate analysis, high Ki67 index and young age of less than 35 years were identified as independent risk factors for relapse (p<0.0001 for Ki67 index and 0.015 for young age). The high risk patients (n=24, 4.5%) who have high Ki67 index (more than 75%, 4+) or young age of less than 35 and more than 50% of Ki67 index showed better RFS with statistical significance for anthracycline-containing adjuvant chemotherapy (p=0.029). Conclusion: A patients’ population may exist who have clinical benefit from adjuvant chemotherapy in T1b-cN0 HR-positive breast cancer patients. Ki67 index and age are useful as valuable surrogate markers to predict recurrence and to have benefit from adjuvant chemotherapy in this population. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P5-01-11.