[301] The Predictive Value of P53 Expression to Anthracycline-Based Neo-Adjuvant Therapy in Triple Negative Breast Cancer Patients

Jian T Yang, Cheng Z Liu, William Dooley, Ronald Squires, Elizabeth Jett, Jeanene Parker. OUHSC, Oklahoma City, OK

Background: Triple negative breast carcinoma (TNBC) is an aggressive tumor without expression of estrogen/progesterone receptors and Her2/Neu. Anthrathycline-based neoadjuvant therapy (ABNT) is routinely used in high stage TNBC patients. It is effective in some patients but has serious toxicity. Previously we have found that the extent of response to ABNT in TNBC patients can be categorized into three groups. complete pathologic response (cPR), no response, and partial response. The aim of this study is to assess the predictive value of p53 expression in these distinct responding groups of TNBC patients. Predictive marker study would help for the patient selection for this regimen.
Design: Total 74 TNBC cases are included. 40 are no response/nearly no response cases (tumor reduced <20% of the original size and without marked treatment cytological changes) and 34 are cPR/nearly cPR cases (Microscopically scattered small tumor nests with marked therapeutic degenerative changes). Anti-p53(Bp53-11) immunohistochemical stain is performed using Ventana on formalin fixed paraffin-embedded tissues with appropriate positive and negative controls. The staining results show essentially biphasic distribution and are categorized as positive (diffusely strong stain), negative (no stain or weak stain in less than 50% of tumor cells), and intermediate. The data were assessed by chi-square for statistical significance.
Results: In 40 no response/nearly no response cases, 27 are negative (67.5%) for p53 expression; 11 positive (27.5%); and 2 intermediate (5%). In 34 cPR/nearly cPR cases, 9 are negative (26.5%) for p53 expression, 24 positive (70.5%), and 1 intermediate (3%). For the predictive value of p53 expression to ABNT, the sensitivity is 72% and specificity 71%. The positive predictive value is 69% and negative predictive value 75%. Chi-Square P = 0.0009, <0.001, extremely significant.
Conclusions: The results show that p53 expression is significantly associated with response to ABNT in TNBC patients. Positive p53 expression is in significantly higher numbers of cPR/nearly cPR patients and negative p53 expression is in significant higher numbers of no response/nearly no response patients. The data bank for the study will be expanded to get more statistical power and the mechanism of p53 expression to response to ABNT needs to be further investigated. Other predictive markers also need to be explored.
Category: Breast

Tuesday, March 20, 2012 9:00 AM

Platform Session: Section B, Tuesday Morning

 

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