Optical spectroscopy to monitor tumor response to immunotherapy

We used Diffuse Reflectance spectroscopy (DRS) to investigate functional changes within the tumor microenvironment when treated with different immunotherapy drugs. We injected the CT26 cell line into the flank of 35 mice that were assigned to 4 different groups: anti-PD-1, anti-CTLA-4, combination treatment, and IgG. The 4 groups were injected intraperitoneally on days 1, 4 and 7 (Day 1 – tumor at 80-120 mm3). DRS spectra were acquired simultaneously for 9 consecutive days and a lookup table (LUT)-based inverse model was implemented to decompose the spectral data. We found statistically significant differences in functional changes among the different immunotherapy groups.