Abstract P4-01-06: Diffuse optical tomography can predict pathologic complete response in patients with HER2+ or triple negative breast cancer undergoing neoadjuvant chemotherapy

Background Pathologic complete response (pCR) predicts clinical outcome in women who receive neoadjuvant chemotherapy (NACT) for breast cancer. Identifying who will have a pCR early during NACT has the potential to save patients months of ineffective chemotherapy and limit unnecessary toxicity; however, no method currently is standardly used. Diffuse optical tomography (DOT) uses near-infrared light to measure concentrations of oxyhemoglobin [HbO2], deoxyhemoglobin [Hb], total hemoglobin [HbT], and oxygen saturation [SO2%], and can assess tissue structure and vascularity. As it is inexpensive, fast, and does not require radiation or intravenous contrast no radiation nor IV contrast, DOT has the potential to become an integral part of NACT to predict responses to NACT. Given the particular significance for pCR in HER2+ and triple negative breast cancer (TNBC), we prospectively evaluated whether a 2 week change in DOT parameters could predict pCR after 5 months of NACT in these subtypes. Methods We conducted a prospective cohort study of women with stage II-IIIC breast cancer scheduled to receive NACT with 12 weeks of weekly taxol and four cycles of doxorubicin with cyclophosphamide (AC). We evaluated the associations between residual cancer burden (RCB: 0-3; pCR= RCB 0) and changes in DOT measures. Optical imaging was performed at baseline and before the following: Taxol #3, Taxol #5, AC #1, AC #2, and surgery. Correlation and t-testing were used to evaluate the relationship between 2-week DOT changes and pathologic response. Results In a prospectively accrued, longitudinal clinical study with DOT, at least 20 patients with HER2+ or TNBC were enrolled. For patients with these tumor subtypes, there was a significant association between pCR after 5 months of NACT (i.e. RCB 0) and change in the following DOT parameters comparing baseline to after 2 weeks of taxol: HBO (p=0.02), HBT (p=0.02), and S02% (p=0.03). No significant association was seen with HB (p=0.20) or water (p=0.85). When looking specifically at patients with TNBC (n=at least 8 patients), these associations were particulars strong between pCR and the following DOT parameters: HBO (p=0.004), HBT (p=0.009), and S02% (p=0.04). Additional patients are anticipated in this study are anticipated to complete NACT and will be reported at SABCS. Conclusions Optical imaging can provide imaging biomarkers to monitor breast cancer response to NACT. Early predictions of pathologic response to NACT can be made with high accuracy as early as two weeks after treatment initiation. These findings are specifically strong in TNBC, a group for whom pCR is predictive of clinical outcome. Citation Format: Kalinsky K, Lee S, Zhong X, Lim EA, Gunther JE, Hibshoosh H, Kim HK, Accordino M, Crew K, Hielscher A, Hershman DL. Diffuse optical tomography can predict pathologic complete response in patients with HER2+ or triple negative breast cancer undergoing neoadjuvant chemotherapy [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 P4-01-06.