Methods for detecting inactivation of the homologous recombination pathway (brca1/2) in human tumors

A method for predicting tumor deficiency in the DNA homologous recombination (HR) pathway in a patient suffering from cancer, comprising the steps consisting of:

• determining the ploidy of the tumor sample;
• quantifying the number of rearrangements in the genomic DNA of a tumor sample obtained from said patient;
• comparing the number of rearrangements per genome to a reference, wherein a number of rearrangements resulting in segments of at least 3 megabases superior to said reference is indicative of HR deficiency.

A method for treating cancer in a patient, comprising the steps of:

• quantifying the number of rearrangements in the genomic DNA of a tumor sample obtained from said patient, wherein the number of rearrangements corresponds to the number, per genome, of breakpoints resulting in segments of at least 3 megabases, preferably at least 4 megabases, even more preferably at least 5, 6, 7, 8 9, 10, 11 12, 13, 14, 15, 16, 17, 18, 19 or 20 megabases.
• comparing said number of rearrangements to a predetermined reference;
• administering a therapeutically effective amount of a PARP inhibitor and/or an alkylating agent, if said patient has a number of rearrangements superior to said reference.