Combined diffuse optical spectroscopy and contrast-enhanced magnetic resonance imaging for monitoring breast cancer neoadjuvant chemotherapy: a case study

Monitoring tumor response to therapy can enable assessment of treatment efficacy, maximizing patient outcome and survival. We employ a noninvasive, handheld laser breast scanner (LBS) based on broadband diffuse optical spectroscopy (DOS) in conjunction with contrast-enhanced magnetic resonance imaging (cMRI) to assess tumor response to presurgical neoadjuvant chemotherapy. DOS and cMRI scans are performed after the first and fourth cycles of a doxorubicin/cyclophosphamide regimen in a patient with invasive ductal carcinoma. DOS measurements are used to quantify bulk tissue optical and physiological parameters, which are mapped to $T2$- and $T1$-weighted cMRI images. Initial DOS measurements show high tumor/normal contrast in total hemoglobin concentration (THC, $56±7$ versus $27±4μM$) and water fraction ($81.4±1%$ versus $24±3%$) colocalized with regions of strongly enhancing $T2$-wieghted and cMRI signals. After the fourth cycle of chemotherapy, we observe decreases in peak MRI contrast-enhancement values (37.6%) and apparent lesion volume (21.9 versus $13.7cm3$), which corresponds to physiological changes measured by DOS, including a 20 to 25% reduction in the spatial extent of the tumor and a 38.7% drop in mean total hemoglobin content (THC, 41.6 versus $23.4μM$). These data provide in vivo validation of the accuracy of broadband DOS and the sensitivity of optical methods to changes in tumor physiology.