In certain embodiments, the present invention, the present invention provides a method of treating a cancer in a subject, comprising: (a) administering to the subject a predetermined dosage of an anti-CTLA4 antibody (b) detecting the level of the anti-CTLA4 antibody in a sample of the subject and (c) increasing the dosage of the anti-CTLA4 antibody in the subject if the level of the anti-CTLA4 antibody from step (b) is below a threshold exposure level, such that the cancer is treated.