A method for determining, modulating or adjusting a treatment regimen with a chemotherapeutic agent in a patient affected with a colorectal cancer, wherein said agent is able to leverage or promote a tumor-targeted immune response, preferably by causing immunological cell death, said method comprising a) quantifying at least two biological markers which are CD8 and CD3 in a tumor sample from the patient, and b) comparing the values obtained in a) to predetermined reference values, and c) deciding to increase the exposure of the patient to the chemotherapeutic agent by deciding to increase the dose, the duration of treatment and/or the frequency of administration, when the values obtained in a) are superior to a predetermined reference value; wherein step a) is performed by quantifying the density of CD3+ cells in center of the tumor, the density of CD8+ cells in the center of the tumor, the density of CD3+ cells in the invasive margin, and the density of CD8+ cells in the invasive margin; wherein step b) further comprises classifying the patient in groups (Low, Intermediate, or High Immunoscore) as follows: Low IS corresponds to a mean percentile below 25%, Intermediate IS corresponds to a mean percentile between 25% and 70%, High IS corresponds to a mean percentile above 70%; wherein the mean percentile refers to the mean percentile of the 4 individual percentiles of the 4 markers (CD3ct, CD8ct, CD3im, CD8im) corresponding to the density of CD3 cells in CT and IM regions and the density of CD8 cells in CT and IM regions; wherein the chemotherapeutic agent is oxaliplatin, optionally combined with 5-fluorouracil and/or capecitabine; wherein, when the patient has been classified as belonging to the intermediate or high IS group, deciding to adjust the duration of the treatment regimen with the chemotherapeutic agent to at least six months, and the oxaliplatin dose to at least a cumulative dose of 700 mg/m 2 said method comprising a) quantifying at least two biological markers which are CD8 and CD3 in a tumor sample from the patient, and b) comparing the values obtained in a) to predetermined reference values, and c) deciding to increase the exposure of the patient to the chemotherapeutic agent by deciding to increase the dose, the duration of treatment and/or the frequency of administration, when the values obtained in a) are superior to a predetermined reference value; wherein step a) is performed by quantifying the density of CD3+ cells in center of the tumor, the density of CD8+ cells in the center of the tumor, the density of CD3+ cells in the invasive margin, and the density of CD8+ cells in the invasive margin; wherein step b) further comprises classifying the patient in groups (Low, Intermediate, or High Immunoscore) as follows: Low IS corresponds to a mean percentile below 25%, Intermediate IS corresponds to a mean percentile between 25% and 70%, High IS corresponds to a mean percentile above 70%; Low IS corresponds to a mean percentile below 25%, Intermediate IS corresponds to a mean percentile between 25% and 70%, High IS corresponds to a mean percentile above 70%; wherein the mean percentile refers to the mean percentile of the 4 individual percentiles of the 4 markers (CD3ct, CD8ct, CD3im, CD8im) corresponding to the density of CD3 cells in CT and IM regions and the density of CD8 cells in CT and IM regions; wherein the chemotherapeutic agent is oxaliplatin, optionally combined with 5-fluorouracil and/or capecitabine; wherein, when the patient has been classified as belonging to the intermediate or high IS group, deciding to adjust the duration of the treatment regimen with the chemotherapeutic agent to at least six months, and the oxaliplatin dose to at least a cumulative dose of 700 mg/m 2