Abstract: A method for predetermining whether a cancer has a probability to become metastatic or recurrent, having the steps of: obtaining a sample cell population; assaying the sample cell population; detecting the rate of change of the sample cell population's pH over time; and comparing the pH change versus a predetermined pH rate of change. Also provided is a method of treating a patient having the steps of: isolating a cancer stem cell from a patient; culturing the cancer stem cell to produce a pool of descendant cells; culturing cells from the pool of descendant cells in the presence at least one compound among: anti-cancer drugs, myeloablative, chemotherapeutic, and immunotherapeutic agents, and a combination thereof; assaying over time, during the step of culturing, hydrogen ion concentration in the set of cells; and selecting a candidate therapeutic regimen for the patient based on a result of the assaying step.