[264] Luminal A Versus Luminal B Tumors: Significance of Proliferation Index in ER Positive HER2 Negative Tumors

E Marchetti, D Dabbs, J Yu, S Beriwal, R Bhargava. Magee-Womens Hospital of UPMC, Pittsburgh, PA

Background: According to gene expression profiling studies, luminal tumors are divided into two groups with distinctly different prognosis. Luminal A (LUMA) tumors have significantly better prognosis than luminal B (LUMB) tumors. The identification of these 2 groups based on immunohistochemistry (IHC) is currently a contentious issue. Several IHC based definitions exist, including the most recently proposed Ki-67 labeling index (LI) cut-off of 14% to distinguish between LUMA and LUMB tumors (JNCI.2009;101:736-750).
Design: In order to examine the validity of several definitions, we studied 56 ER positive, HER2 negative tumors using IHC. These cases were part of a database of tumors subjected to neoadjuvant chemotherapy. All patients have previously received hormonal and chemotherapy. Following pathology parameters were evaluated with respect to tumor recurrence: overall tumor grade, mitosis score, Ki-67 LI (≥14% {high} versus < 14% {low}), progesterone receptor (PR) status, and positivity for androgen receptor (AR) and FOXA1. AR was studied as some studies have suggested relatively good prognosis for AR positive tumors.
Results: Eight patients had recurred and 48 patients were free of tumor at an average follow up period of 47 months. There was no significant difference between tumor size, age and stage between patients who recurred versus those that were free of tumor. Compared to patients that were free of disease, the patients that recurred had a significantly higher Ki-67 labeling index and showed lack of AR. Other variables were not statistically significant.

Table 1
Recurred (n=8)Free of tumor (n=48)P value
Overall tumor gradeGrade 1: 0Grade 1: 80.406
Grade 2: 7Grade 2: 37
Grade 3: 1Grade 3: 3
Mitosis scoreScore 1: 6Score 1: 400.709
Score 2: 2Score 2: 7
Score 3: 0Score 3: 1
Ki-67 LI (n=50)Low: 1Low: 290.003
High: 7High: 13
Average: 31Average: 15
PR status (n=56)Neg: 2Neg: 60.35
Pos: 6Pos:42
AR status (n=49)Neg: 3Neg: 40.04
Pos: 5Pos: 37
FOXA1 status (n=47)Neg: 0Neg: 0NA
NA: Not applicable

Conclusions: This is a small study with limited average follow up information; however the results suggest that following information in ER positive tumors may be of value in predicting prognosis: level of proliferation activity as measured by Ki-67 labeling index, and AR status. FOXA1 is almost always intensely reactive in all ER positive tumors and has limited value in predicting prognosis.
Category: Breast

Monday, March 22, 2010 1:00 PM

Poster Session II # 58, Monday Afternoon


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