A computerized method for determining an objective tumor response to an anti-cancer therapy using cross-sectional images includes receiving a cross-sectional image of digital medical image data, identifying a set of pixels within the cross-sectional image corresponding to a target lesion, and analyzing the set of pixels with an image processing module to identify an upper and lower threshold of pixel intensities within a total range of pixel intensities, define a subset of pixels from the set of pixels that correspond to vascularized tumor and that have pixel intensities greater than or equal to the lower threshold and lower than or equal to the upper threshold, and derive a vascular tumor burden for the set of pixels. The method further includes determining the objective tumor response for the target lesion, wherein the objective tumor response is based on the vascular tumor burden.