Rationale and Objectives
Imaging tumor response to neoadjuvant chemotherapy in vivo offers unique opportunities for patient care and clinical decision-making. Detailed imaging studies may allow oncologists to optimize therapeutic drug type and dose based on individual patient response. Most radiologic methods are used sparingly due to cost, thus important functional information about tumor response dynamics may be missed. In addition, current clinical standards are based on determining tumor size changes, thus standard anatomic imaging may be insensitive to early or frequent biochemical responses. Because optical methods provide functional imaging endpoints, our objective is to develop a low-barrier-to-access bedside approach that can be used for frequent, functional assessment of dynamic tumor physiology in individual patients.
Materials and methods
Diffuse Optical Spectroscopic Imaging (DOSI) is a non-invasive, bedside functional imaging technique that quantifies the concentration and molecular state of tissue hemoglobin, water, and lipid. Pilot clinical studies have shown that DOSI may be a useful tool for quantifying neoadjuvant chemotherapy response, typically by comparing the degree of change in tumor water and deoxy-hemoglobin concentration before and after therapy. Patient response at one week and mid-therapy have been used to predict clinical outcome. In this report we assess the potential value of frequent DOSI monitoring by performing measurements on 19 different days in a 51 year old subject with infiltrating ductal carcinoma (initial tumor size 60 × 27 mm) who received neoadjuvant chemotherapy (Anthracyclines and Bevacizumab) over an 18 week period.
A composite index, the Tissue Optical Index (TOI), showed a significant (~50%) decrease over the nearly 18 weeks of chemotherapy. Tumor response was sensitive to the type of chemotherapy agent, and functional indices fluctuated in a manner consistent with dynamic tumor physiology. Final pathology revealed 4 mm of residual disease, which was detectible by DOSI at the conclusion of chemotherapy prior to surgery.
This case study suggests that DOSI may be a bedside-capable tool for frequent longitudinal monitoring of therapeutic functional response to neoadjuvant chemotherapy.
Keywords: Near-infrared, optical imaging, tissue absorption spectroscopy, breast cancer, therapeutic monitoring