A portable device and system, based upon Diffuse Optical Spectroscopy (DOS), for the detection of surface detectable cancers such as breast cancer and the determination of their response to therapy. The system may include hardware and software components that form a number of subsystems: an Optical-Electronic Subsystem, a Digitization Subsystem, an Optical Parameter Computation Subsystem, an Artificial Intelligence Subsystem, and a Presentation Subsystem. The system can be integrated into a hybrid architecture that utilizes other imaging techniques, such as X-ray mammography, for cancer detection.