Study to Evaluate the Use of Capecitabine in Monotherapy and in Combination With Oxaliplatin in Elderly Patients as Adjuvant Chemotherapy for Locally Advanced Colorectal Cancer.

All patients with locally advanced colorectal cancer after radical surgical intervention who have not previously received systemic antitumor treatment will be randomized into two groups receiving fluoropyrimidines in mono-regimen and in combination with oxaliplatin.

Main objectives:

* to compare the 3-year disease-free survival and 5-year overall survival rates in the two groups.
* to identify, through a comprehensive geriatric assessment among elderly patients, the groups that benefit most from adjuvant chemotherapy.

Patients will be treated until progression of the process is detected or the maximum effect of therapy is reached (the longest duration of treatment is 6 months).

The study is a single-center, open-label, randomized Phase II study. The study will be divided into a screening phase (4 weeks prior to inclusion in the study), a treatment phase (up to 6 months) and a long-term follow-up phase (up to 28 days from the end of treatment - follow-up to assess the safety of therapy, up to 3 years from the end of treatment to assess survival and follow-up).

During the screening phase, patients with MR CRC will undergo examinations to fulfill the inclusion and exclusion criteria for the study.

Next, elderly patients meeting these criteria-who have locally advanced colorectal cancer-will be randomized in a ratio of approximately 1:1 into 2 groups.

The study is planned to include 160 patients, 80 in each group, for a total of 160 patients.

Patient groups

1. Capecitabine in mono-regimen
2. PCT according to XELOX regimen Stratification factors - gender m/f, age \<75 /\>75, presence of postoperative complications yes/no.

The patients will be treated until the progression is detected or the maximum effect of therapy is achieved (the longest duration of treatment is 8 cycles). At the end of the treatment period, all patients will enter the observation phase.

Eligibility Criteria:
Inclusion Criteria:

1. Age 70 years and older;
2. Obtaining informed consent to participate in the study;
3. Morphologically confirmed diagnosis of colorectal cancer;
4. Stage III colorectal cancer;
5. Underwent radical surgical intervention for primary colorectal tumor;
6. ECOG score of 0 - I;
7. Life expectancy of more than 6 months;
8. No history of systemic drug therapy for CRC;
9. Adequate liver, kidney and bone marrow function;
10. Absence of severe uncontrolled concomitant chronic diseases and acute illnesses.

Exclusion Criteria:

1. Having previously received any systemic therapy for CRC;
2. Time after surgical treatment of more than 12 weeks;
3. Stage I-II and IV disease;
4. Confirmed dihydropyrimidine dehydrogenase deficiency in blood by PCR (alteration of alleles c.\[190511G \> A\], c.\[1679T \>G\],\[2846A \> T\], \[1129-5923C \>G\], \[c.1236 G\>A(HapB3)\]);
5. Severe uncontrolled comorbid chronic diseases or acute illnesses;
6. Presence of a second malignancy (except for previously cured malignancies);
7. Any condition that, in the opinion of the physician, would interfere with the study procedures.