Abstract P3-06-26: Serum anti-p53 antibody titers predict pathological response to preoperative chemotherapy in women with HER2 positive or triple negative breast cancer

Background: In SABCS 2009, we reported that the high level of serum anti-p53 antibody titers was associated with response to preoperative chemotherapy in cases with primary breast cancer (SABCS 2009). Prognostic meaning of pathological complete response (pCR) after preoperative chemotherapy differs among various subtype, and there is a close relationship between pCR and prognosis in cases with HER2 positive or triple negative disease. The aim of this study is to evaluate the association between the high level of serum anti-p53 antibody titers and pCR in patients with HER2-positive or triple negative breast cancer. Patients and Methods: In this study, we analyzed 196 women with operable early stage breast cancer (T1-T3, N0-1) treated with preoperative chemotherapy and definitive curative surgery since 2002 to 2011. All of the patients received four cycles of FEC (fluorouracil 500 mg/m2, epirubicin 100 mg/m2, cyclophosphamide 500 mg/m2 q3w) followed by four cycles of docetaxel (75 mg/m2 q3w). The serum anti-p53 antibody titers were assessed by ELISA with the anti-p53 EIA Kit II (MESACUP anti-53 Test: MBL) in the pre-treatment serum samples. The test's cut-off value was determined to be 1.3 IU/ml based on reference distribution in healthy control individuals. The association between serum anti-p53 antibody titers and pCR was analyzed. Results: The subtype of tumors of 196 patients were classified to 86 of ER+/HER2−, 24 of ER+/HER2+, 29 of ER−/HER2+ and 57 of ER−/HER2−. The pCR was achieved 49 of 196 patients (25%). The pCR rate were 7%(6/86), 33%(8/24), 48%(14/29) and 37%(21/57) in the subtype of ER+/HER2−, ER+/HER2+, ER−/HER2+ and ER−/HER2− respectively. The range of serum anti-p53 antibody titers in the serum samples of 196 patients was between 0.40 and 5610 (the median was 0.40 and the average was 85.2). Excluding 86 cases with ER+/HER2−, relationship between serum anti-p53 antibody titers and pCR was evaluated. According to serum anti-p53 antibody titers with the patients of pCR, cut-off value of serum anti-p53 antibody titers was set to be 6 IU/ml. The pCR was observed in nine of 12 cases (75%) with high serum anti-p53 antibody titers, which was significantly higher than those with low titers (35%: 34/98; p = 0.01). Multivariate analysis showed that the only high anti-p53 antibody titer was an independent predictive factor for pCR due to preoperative chemotherapy (p = 0.01). Conclusion: p53 mutation analysis using serum anti-p53 antibody titers might be a useful predictive test for response to preoperative chemotherapy in patients especially with HER2 positive or triple negative breast cancer. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P3-06-26.