CancerPal, based on the input of two measurements of tumor size in cm or tumor-marker values calculates a tumor-specific exponential growth function which it uses to calculate the tumor-specific and marker-specific growth, acceleration and deceleration growth rates of tumors in the presence or absence of therapy. The calculations include tumor volume and marker doubling times as well. The App lets physicians monitor precisely the response to therapies by comparing tumor growth to the projected growth value, which more accurately reflects drug effects.