A system and method for tracking a tumor includes a regression module for selecting, using a motion signal and a regression function, a feature signal from a set of feature signals, each feature signal in the set of feature signals represents a medical image of the body of the patient, wherein the motion signal represents a motion of a surface of a skin of the patient caused by the respiration, and wherein the regression function is trained based on a set of observations of the motion signal synchronized with the set of feature signals； and a registration module for determining the location of the target object using the feature signal and a registration function, wherein the registration function registers each feature signal to a breath-hold location of the target object identified.
