Picture 3. Higher grade tumors are more frequently Ki67 positive Prognostic impact of Ki-67 in Croatian women with early breast cancer (single-institution prospective observational study) Ivan Bilić, Natalija Dedić Plavetić, Marko Kralik*, Paula Podolski, Ana Koši Kunac, Damir Vrbanec Department of oncology, University Hospital Center Zagreb, Croatia *Department of radiology, University Hospital Center Zagreb, Croatia INTRODUCTION Ki-67 is increasingly gaining attention as important proliferation marker in breast cancer. It is considered to be relatively easy assayed by commercialy available kit for immunohistological annalysis of tumor tissue. However, despite it is widely adopted, it is still under scrutiny concerning the role in therapeutic decision-making. We found data on prognostic factors in Croatian women suffering from early breast cancer scarcely published. Here we present single-institution data on proliferation marker Ki-67 in patient cohort with primary operable breast cancer treated in Breast cancer unit of University Hospital Center Zagreb during years 2002 and 2003. Table 1. Description of the patient cohort (N=209) Age (yr) Mean 57,63; St.dev. 12,089; Median 56; Min 30; Max 87 Menopause (n) 135 Tumor type (n) Ductal - 129, Lobular - 44, Mixed - 11, Other - 31 Hystological grade (n) I - 33, II - 110, III - 72 ER positive (n) PR positive (n) 110 Her-2 positive (n) 35 Ki-67 (%) Mean 11,4; St. dev. 12,88; Median 7,2; Min 2; Max 64 Ki-67 <= 14% (n) 160 Follow-up (yr) Mean 8,127, St.dev. 2,756 Median 9,38, Min 0,397, Max 10,412 Died (n) 51 Relapse (n) 61 Died without relapse (n) 14 Relapse site (n) Local 16, Distant 41, Both 2, Contralateral 2 Picture 1. Overall survival is significantly lower in Ki67 positive group. MATERIALS AND METHODS Final total number of patients (pts.) was 209 pts (215 patients started; 6 were excluded being initially metastatic, or lost to follow-up). Median age at diagnosis was 56 years (min 30, max 87). Median follow up is 9.38 years (min 8 months, max 10.4 years). 135 pts. were menopausal at diagnosis. All pts. were diagnosed by pathohistological examination of extirpated tumor including immunohistochemistry (IHC) for estrogen (ER) and progesterone (PR) receptor, as well as Her-2 and Ki-67 determination. Her-2/neu confirming methods were FISH or CISH for suspected amplification (++ by IHC). Adjuvant therapy followed according to TNM stage and accepted ESMO guidelines, with exception of adjuvant trastuzumab, which was not reimbursed by health insurance at that time. Pts. were grouped according to Ki-67 expression (cut-off value 14% - percentage of positive nuclei per hundred tumor cells), grade, stage and ER/PR/Her-2 profiles (five breast cancer subtypes according to St. Gallen recommendations). Kaplan-Meier curve with log-rank test, or Kruskal-Wallis, Mann-Whitney test with Bonferroni correction were used for univariate, and Cox regresion analysis for multivariate models. Picture 2. Ki67 is significantly higher among patients who died during follow-up period 16 (mean) Picture 3. Higher grade tumors are more frequently Ki67 positive 9,67 (mean) RESULTS Overall survival (OS) significantly differs in Ki-67 positive vs. negative group (positive >14%, OS=77.9 vs. 62.2, p=0.023). Accordingly, pts. that died during follow-up have significantly higher Ki-67 value (16 vs. 9.67, p=0.003). DFS was not significantly affected by Ki67 positivity (data not shown). Ki-67 value correlated with histologic grade (10 vs. 16.8 vs. 38.9% in grades I to III, respectively – p<0.001, χ2=15.204). Kruskal-Wallis analysis confirmed non-equity of Ki-67 among grade-groups, but non-parametric test between I and II grade failed to reach statistic significance. Tumor grade had prognostic impact on OS (after 10 years, 90.1vs.77.7 vs. 57.4 in grades I to III, respectively – p=0.006) and on disease free survival (DFS) as well. Stratification according to five molecular intrinsic subtypes of breast cancer, using ER/HR/Her-2 and Ki-67 (luminal A (1) and B (2), Her-2 enriched luminal (3) and non-luminal (4) and (5) triple-negative) revealed significantly lower Ki-67 expression in luminal A-like and significantly higher in luminal B-like group than Her-2 enriched and triple negative-like groups (P<0.005). In multivariate regression analysis Ki-67 expression did not reveal significant impact on OS and DFS of patients stratified in aforementioned subtype-like groups. Picture 4. Overall survival is significantly lower among patients with higer tumor-grade Picture 5. Relapse is more frequent when tumor-grade is higher CONCLUSIONS Ki-67 alone had prognostic value for OS at 10 years follow-up in our cohort. Ki-67 level and tumor grade showed correlation, mostly significant, but tumor grade appeared to have stronger prognostic value than Ki-67. Grouping in molecular intrinsic-like subtypes of breast cancer according to IHC measurements of ER/PR/Her-2/Ki-67, showed Ki-67 difference between luminal A and B-like and the rest of subtypes, but failed to show prognostic impact concerning OS and DFS between groups.