Abstract P6-09-12: Using multiphoton laser scanning microscopy to assess neoadjuvant therapy outcome in core needle biopsies: A novel methodology

Background : Over-expression of Human Epidermal Growth Factor receptor-2 (HER2) in breast cancer is associated with an aggressive clinical course and poor prognosis. Targeting HER2 over-expression has been shown to be a remarkably effective therapeutic modality in the metastatic, adjuvant and neoadjuvant setting and the pathologic response to neoadjuvant treatment in HER2-positive breast cancer has been shown to be an excellent surrogate for a good outcome. The stromal tumor microenvironment is implicated in fostering tumor growth, facilitating cell migration and ultimately resulting in metastatic disease. Specifically, the collagenous extracellular matrix, which includes fibrillar collagen, has been suggested to play a role in the migration of malignant breast epithelial cells within the surrounding stroma. We have developed a novel methodology which uses an intrinsic optical signature to quantitatively evaluate fibrillar collagen (Burke et al. BMC Cancer 15 (2015): 929). Here, we evaluate the ability of this quantitative methodology to predict the pathologic response after neoadjuvant HER2-targeted treatment as assessed by the Residual Cancer Burden score/class (RCB). This quantitative evaluation in pre-treatment biopsies is then correlated with the pathologic response to treatment in the post-therapy resection. Material and Methods : Clinical pathologic variables for 29 cases of HER2-positive breast cancer that had undergone neoadjuvant chemotherapy plus HER2-targeted therapy were retrieved from the medical record database at URMC, including the post-treatment RCB score and ER/PR/HER2 status. Second harmonic generation (SHG) is an intrinsic optical signal produced by fibrillar collagen. To quantify collagen microstructure in the pre-treatment core biopsy, we used SHG imaging to determine the average forward to backward-light scattering ratio (F/B). The F/B ratio is sensitive to structural properties of collagen fibers. Results: Logistic regression was used to assess the association between F/B and the binary response variable RCB class (0/1 or 2/3). A likelihood ratio test was used to calculate the p-value to test whether the regression coefficient for F/B was zero (i.e. no effect) in the tumor-stromal interface. The average F/B ratio at the leading edge of the tumor stratified by RCB class is shown in Table 1. When evaluated in the bulk of the tumor tissue, F/B was not correlated with RCB status; however, when evaluated at the leading edge of the tumor stromal interface, F/B was significantly correlated with RCB status (p=0.035). Conclusions : We have previously shown that the measurement of F/B in the primary tumor after resection is an independent prognostic indicator of metastasis-free survival in breast cancer. Our results in the current study furthers these observations and suggests that the evaluations of the microstructure of collagen fibers by F/B measurement from the pre-treatment biopsy, specifically at the leading edge of the tumor-stroma interface, may be useful for predicting pathologic response to trastuzumab-based neoadjuvant therapy. Further studies in a larger patient cohort are warranted. Citation Format: Desa DE, Turner BM, Buscaglia B, Hill RL, Strawderman RL, Hicks DG, Brown EB. Using multiphoton laser scanning microscopy to assess neoadjuvant therapy outcome in core needle biopsies: A novel methodology [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-09-12.