Prof Dr. Al. Trestioreanu Bucharest Institute of Oncology, Bucharest, Romania
Oana Gabriela Trifanescu , Liviu Bilteanu , Silvia Ilie , Diana Maria Bran , Inga Safta , Laurentia Minea Gales , Rodica Maricela Anghel
Background: Ki-67 is one of the most critical prognostic proliferation markers in breast cancer, used on a large scale by oncologists to select treatment options. This study aimed to validate Ki-67 as a prognostic marker and establish the optimal Ki67 cut-offs for stratifying patient prognosis and treatment decisions. Methods: Medical files of 582 consecutive patients with early breast cancer (stage IB-IIIA) who underwent surgery as a first treatment in our institution between 2005-2019 were retrospectively reviewed. Values of Ki-67 were divided into 5 categories: 0-9%, 10-19%, 20-29%, 30-39%, and more than 40%. Results: Kolmogorov-Smirnov and Shapiro-Wilk tests showed that the patient’s age (yrs) at diagnostic, Ki-67 (in %), tumor size (in mm), estrogen and progesterone receptors abundance (%), exhibit normal distributions (p < 0.05). Median age at diagnosis was 54.8 (± 11.5) years and mean Ki-67 of 25.5 ± 16.5 and a median value of 20. Stage distribution was: stage IB 5.5%, IC 12%, IIA 46.6%, IIB 20.4%, IIIA 15.5%. The mean tumor dimension at diagnosis was 21.3 mm. After a median follow-up of 48 months (6-118), estimated disease-free survival rates (DFS) for all patients at 3 and 5 years were 92% and 79%. Disease-free survival rates at 5 years was 96% for patients with Ki-67 0-9%, 90% for patients with Ki-67 10-19%, 80% for patients with Ki-67 20-29%, 75% for patients with Ki-67 30-39%, and 72% for patients with Ki-67 more than 40%. The difference between the median DFS and each ki67 category was statistically significant (p < 0.0001). Using the fit of mixture method, we identify a new cut-off of 29% that negatively predicts DSF for patients (HR = 4.51 95% CI = 1.69-12.04, p = 0.001). Pearson correlation coefficients (p < 0.05) for Ki-67 and DFS, age, ER%, PR%, p53, and tumor size were -0.110, -0.096, -0.139, -0.136, 0.301, and 0.175, respectively. Moreover, DFS was also negatively correlated (p < 0.01) with the patient’s age (-0.106) and tumor size (-0.180). Though the correlation coefficients were small, they oriented the creation of linear models of DFS as a dependent variable and Ki-67, tumor size, and age. DFS has a statistically significant dependence only on the first two variables (standardized coefficients -0.103, p = 0.045 and -0.161, p = 0.02). Conclusions: Ki-67 is a strong prognostic factor in early breast cancer patients. New Ki-67 cut-off levels that may be used in clinical practice were identified. In addition, multivariate analysis showed a significant statistical influence of other factors, such as Ki67 and tumor size. Such correlations can be the basis of a scoring system for progression risk.
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