Abstract P1-09-15: Tumor and serum DNA methylation in women receiving preoperative chemotherapy (PST) with or without vorinostat in primary operable HER2-negative breast cancer in TBCRC008

Abstract

Abstract Background: DNA methylation is a promising prognostic and predictive biomarker of response to treatment in advanced breast cancer (Fackler MJ. Can Res 2014). We evaluated whether baseline and change in tissue and serum methylation would predict pathological complete response (pCR) in patients with HER2-negative early breast cancer treated with PST. Methods: TBCRC008 was a multicenter placebo-controlled trial that investigated pCR (no invasive cancer in breast/axilla) following 12 weeks of preoperative carboplatin and albumin-bound paclitaxel with or without the histone deacetylase (HDAC) inhibitor vorinostat in 62 patients with HER2-negative breast cancer. We performed an exploratory planned biomarker study correlating baseline and change (D15) in tumor tissue and serum methylation with pCR. Methylation was measured using cumulative methylation index (CMI) in quantitative multiplexed methylation-specific polymerase chain reaction (QM-MSP) assays; cMethDNA assay for serum (Fackler MJ. Can Res 2014) and QM-MSP for tissue (Fackler MJ. Can Res 2004). The analysis population included all patients with available methylation and pCR data. Association between CMI level (log transformed baseline, D15, change) and pCR was evaluated using univariate as well as multivariable logistic regression models controlling for treatment arm and estrogen receptor (ER) status. Additional subgroup analyses assessed association of CMI level with pCR stratified by ER status and treatment arms, respectively. Spearman's correlation coefficient was performed to evaluate the correlation between tissue and serum CMI. Results: pCR data were available for 61 of 62 patients. One patient with unknown response was treated as a non-responder. The pCR rate was similar in both arms (vorinostat 25.8%, placebo 29%). Both tissue and serum CMI data were available in 55 (baseline), 50 (D15) and 46 (change) patients. Elevated serum methylation based on a predefined threshold (6.9 units) was identified in 23/59 (39%) patients. In univariate analysis, one log unit increase in tissue CMI levels at D15 was associated with a 40% lower chance of obtaining a pCR (odds ratio, OR=0.60, 95% CI 0.37-0.97; p=0.037). The multivariable analysis did not show a statistically significant association of tissue or serum CMI with pCR, although a similar trend in magnitude towards association with pCR was observed for D15 and change in tumor tissue CMI (OR 0.67 and 0.57, p=0.129 and 0.147 respectively). Subgroup analyses suggested a significant association between tissue CMI levels at D15 and pCR in the group treated with vorinostat [tissue OR: 0.44 (0.20, 0.93), p=0.03; serum OR 0.37 (0.13, 1.07), p=0.07] but not in the placebo group. No significant correlation was observed between tissue and serum CMI. Conclusion: This is the first study to evaluate the predictive role of tissue and serum methylation (CMI) in patients with early breast cancer treated with PST ± an HDAC inhibitor. Methylation was detected more frequently in tissue than serum. Tissue CMI levels at D15 may predict poor response to this regimen. Further evaluation of the predictive role of methylation in early breast cancer is warranted. Citation Format: Connolly RM, Fackler MJ, Zhang Z, Zhou XC, Goetz MP, Boughey JC, Walsh B, Carpenter J, Storniolo AM, Watkins S, Barielson E, Sukumar S, Stearns V. Tumor and serum DNA methylation in women receiving preoperative chemotherapy (PST) with or without vorinostat in primary operable HER2-negative breast cancer in TBCRC008 [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-09-15.