Methods for predicting negative consequences of a treatment of a patient with a therapy comprising determining the genetic status of the patients tumor with respect to p53 by determining in a sample of body fluid or a tissue sample of the patient containing tumor cells or cell-free tumor DNA whether the whole p53 gene is present in native form or whether the p53 gene has one or more mutations. In further embodiments the patient is predicted to be a patient who will suffer negative consequences of a therapy interfering with the cell cycle if the whole p53 gene is present in native form and a patient who will suffer negative consequences of a therapy inducing p53 dependent apoptosis if the p53 gene has one or more mutations. Methods of treatment are also contemplated.
