An in vitro method of prognosis for the response to a treatment of an individual suffering from chronic myeloid leukemia, based on a leukemic biological sample taken from said individual, said method comprising: a. a step of measuring the expression level of the genes from at least one subgroup of genes chosen from a group of genes, said group of genes consisting of 25 genes, said 25 genes comprising or consisting of the nucleic acid sequences as set forth in SEQ ID NO: 1 to SEQ ID NO: 25, said subgroup consisting in 7 genes, said 7 genes comprising or consisting of the nucleic acid sequences as set forth in SEQ ID NO: 1 to SEQ ID NO: 7, a value of the measured expression level being obtained for each of the genes of said subgroup, b. a step of comparing the value attributed to the preceding step with each of said genes of said subgroup to the value attributed to each of said genes of said subgroup obtained from a healthy biological sample, in order to obtain a ratio for each of said genes of said subgroup of the expression level in the leukemic biological sample to the expression level in the healthy sample, and c. a step of determining a score S according to the following formula S = ∑ ratio i − ∑ ratio j where ratio i and ratio j represent respectively the ratios obtained for said genes of said subgroup comprising or consisting of the nucleic acid sequences as set forth in SEQ ID NO: i or SEQ ID NO: j, where i and j are integers, i varying from 1 to 5 and j varying from 6 to 7, so that: - if S is less than 1, said individual will have more than around a 40% chance of having a major molecular remission one year after the start of treatment with a first-generation tyrosine kinase inhibitor, and - if S is greater than or equal to 1, said individual will have less than around a 40% chance of having a major molecular remission one year after the start of treatment with a first-generation tyrosine kinase inhibitor. a. a step of measuring the expression level of the genes from at least one subgroup of genes chosen from a group of genes, said group of genes consisting of 25 genes, said 25 genes comprising or consisting of the nucleic acid sequences as set forth in SEQ ID NO: 1 to SEQ ID NO: 25, said subgroup consisting in 7 genes, said 7 genes comprising or consisting of the nucleic acid sequences as set forth in SEQ ID NO: 1 to SEQ ID NO: 7, a value of the measured expression level being obtained for each of the genes of said subgroup, b. a step of comparing the value attributed to the preceding step with each of said genes of said subgroup to the value attributed to each of said genes of said subgroup obtained from a healthy biological sample, in order to obtain a ratio for each of said genes of said subgroup of the expression level in the leukemic biological sample to the expression level in the healthy sample, and c. a step of determining a score S according to the following formula S = ∑ ratio i − ∑ ratio j where ratio i and ratio j represent respectively the ratios obtained for said genes of said subgroup comprising or consisting of the nucleic acid sequences as set forth in SEQ ID NO: i or SEQ ID NO: j, where i and j are integers, i varying from 1 to 5 and j varying from 6 to 7, so that: - if S is less than 1, said individual will have more than around a 40% chance of having a major molecular remission one year after the start of treatment with a first-generation tyrosine kinase inhibitor, and - if S is greater than or equal to 1, said individual will have less than around a 40% chance of having a major molecular remission one year after the start of treatment with a first-generation tyrosine kinase inhibitor. where ratio i and ratio j represent respectively the ratios obtained for said genes of said subgroup comprising or consisting of the nucleic acid sequences as set forth in SEQ ID NO: i or SEQ ID NO: j, where i and j are integers, i varying from 1 to 5 and j varying from 6 to 7, so that: - if S is less than 1, said individual will have more than around a 40% chance of having a major molecular remission one year after the start of treatment with a first-generation tyrosine kinase inhibitor, and - if S is greater than or equal to 1, said individual will have less than around a 40% chance of having a major molecular remission one year after the start of treatment with a first-generation tyrosine kinase inhibitor. - if S is less than 1, said individual will have more than around a 40% chance of having a major molecular remission one year after the start of treatment with a first-generation tyrosine kinase inhibitor, and - if S is greater than or equal to 1, said individual will have less than around a 40% chance of having a major molecular remission one year after the start of treatment with a first-generation tyrosine kinase inhibitor.