"Liquid biopsy" is a collective term that refers to the analysis of cancer-derived biomarkers isolated from the biological fluids of cancer patients. The analysis of these blood components can be used for early cancer detection, staging, prognosis, drug resistance monitoring, and minimal residual disease (MRD) monitoring. The "liquid biopsy" is based on the fact that cancer cells release their DNA into the bloodstream, known as ctDNA (circulating tumor DNA). A sample of the patient's peripheral blood is sufficient to test ctDNA. There have been many studies in the literature on the usefulness of liquid biopsy in the treatment of various malignancies, such as breast cancer, prostate cancer, and colorectal cancer. However, this has been a lack of prospectively obtained data analyzing the impact on the ctDNA assessment of the progression and recurrence of the primary disease or the type of treatment applied to improve long-term survival. The ctDNA test is not a widely recognized technology for assessing the progression of neoplastic disease.

Aim of the study/research hypothesis: the aim of the project is to clinically validate the value of the ctDNA test as a tool for early diagnosis of recurrence, assessment of cancer progression, the prognosis of treatment effects, and monitoring of therapy in patients with primary liver HCC or colorectal cancer metastases.

Description of the methodology: The main objective of the work will be achieved through the implementation of specific objectives: 1) Recruitment of 300 patients, including 100 patients with colorectal liver limited metastasis, 100 patients with hepatocellular carcinoma (HCC) and 100 patients in the control group who will be qualified for liver resection or transplantation, and in whom ctDNA level testing will not be tested. 2) Taking blood samples from the patients. The detection of ctDNA requires only the collection of 10 ml of the patient's blood and the collection of specimens from the tumor after resection. Blood will be collected before, one month, and 6 months after surgery during routine oncology check-ups. Tumor specimens will be taken from the backside table and sent for final histopathological examination. Control "follow-up" will take place for 18 months from the first ctDNA blood collection.

Based on the collected material, genetic analysis will be performed. In the first stage, a tumor section taken during liver resection, and DNA from the patient's blood will be analyzed the molecular (genetic) signature of the patient's tumor will be determined and several genetic changes characteristic of the change will be selected. Thereafter, the presence of the selected genetic variants will be assessed qualitatively and quantitatively in the pre-operative blood sample and all subsequent post-operative blood samples.

The investigators assume that in a blood sample taken 4 weeks after surgery, ctDNA should be undetectable or detected at a low level. In order to assess the change in the level of ctDNA in the postoperative period, a third examination will be performed - 6 months after the operation. Any level of detected ctDNA will be considered significant.

Each increase in the level of the analyzed mutations will indicate the potential progression of the disease. The results of molecular analyzes will be correlated with the assessment of imaging tests and the level of tumor markers performed as part of routine oncological control.

This is a prospective observational study with a defined study group. These are patients with colorectal cancer metastases limited to the liver, i.e. stage IV of the cancer process, or patients with hepatocellular carcinoma (HCC) qualified for radical surgery or liver transplantation. Patients in the control group (without ctDNA tests) will be treated in accordance with the best clinical knowledge and accepted international recommendations.

The statistical analysis of the results will use the SAS (Statistical Analysis System) software, considering the Kaplan-Meier method, log-rank tests, Cox proportional hazards regression, and logistic regression.

The investigators hypothesize that the use of ctDNA will enable the identification of early disease progression or will identify patients with the highest risk of recurrence. In addition, it will improve the supervision of diseases and enable possible modification of treatment in patients with stage IV colorectal cancer or patients after liver resection or transplantation for HCC. In the future, oncological prevention will consist in blood tests, which will enable early detection of even those cancers that show symptoms only at an advanced stage, which will potentially improve the effectiveness of treatment.

Health problem Hepatocellular carcinoma (HCC) is the most common primary malignant tumor of the liver. It is estimated that it accounts for 80-90% all cases of liver cancer. Liver cancer is one of the faster growing and worse prognosis cancers. It constitutes approximately 5.4% of all malignant tumors.

Colorectal cancer (CRC) is currently the third most common cancer in the world and in Poland. Every year in the Polish population about 20,000 people will be diagnosed with colorectal cancer. Most of them will be diagnosed in the advanced stage IV of the disease. About 50% of CRC patients will develop liver metastases during the natural course of disease progression. Surgery for liver metastases is the only potential treatment. Even after tumor resection surgery, the disease may continue to develop even if the patient is undergoing chemotherapy.

Furthermore, the accuracy and sensitivity of pathological and imaging methods for disease progression or molecular identification of residual disease (MRD) are limited, while when the specificity and clinical diagnostic utility of serum markers (CEA) is poor. CT/MRI/PET being part of the standard surveillance program increases ability to detect recurrences, but are not sensitive enough for small lesions, especially in patients after liver resection or modern chemotherapy, i.e. targeted therapy. Most patients have no measurable disease based on imaging until an obvious recurrence occurs. Often it is too late for any intervention. Each recurrence of the disease is also a failure of the chemotherapy. In addition, second line chemotherapy is less likely to work success in terms of long-term patient survival. Therefore, there is an urgent need to improve approaches to long-term non-invasive tumor monitoring and predict recurrence earlier than standard imaging, and to evaluate the effect of surgical intervention and chemotherapy, especially in stage IV cancer.

The awarding criterion - HCC is a rare disease. Awarding criterion - the area of surgery and diagnostics.

In the case of patients with colorectal cancer, the target group of patients to be included in the study are patients over 18 years of age with metastases of colorectal cancer. Colon limited to the liver, with no history of cancer other than colorectal cancer. The study will include synchronous and metachronous metastases according to: new definition.

In the case of hepatocellular carcinoma (HCC), the target group is patients with resectable HCC, in the case of liver resection or unresectable HCC in the case of liver transplantation. The study will include patients with or without cirrhosis. Qualification for liver transplantation and indication for transplantation liver disease will be taken into account, among others, using the French model of HCC (calculator), which takes into account the size and number of lesions and the AFP level.

Patients with or without cirrhosis will be qualified for liver resection. The group will include patients from the age of 18 to the age of 75 in the case resection and all patients qualified for liver transplantation at the liver transplantation qualification meeting.

Patients with completely removed primary tumor in the large intestine will be in the study group.

Chemotherapy is not an indication for the study. According to treatment standards, the vast majority of patients with colorectal cancer and/or metastases will undergo treatment chemotherapy. Currently, not enough scientific research has been conducted to determine how and whether chemotherapy administered to patients affects the results ctDNA. Additionally, the study assumes that patients will be covered by the standard of care in this group of patients.

Patients with extrahepatic lesions will not be included in the study. Patients with rapid disease progression on chemotherapy with a 6-month survival period uncertain will not be included in the research. Patients older than 75 years of age will also not be included in the study.

Patients undergoing steroid therapy and diagnosed with autoimmune diseases will not be included in the study.

The goal of surgical treatment is to achieve R0 resection of all liver metastases. Patients after liver resection with radiologically visible recurrence will undergo treatment further treatment according to the decision of the oncology team. Hepatic and extrahepatic recurrence does not exclude the patient from the study.

Detailed treatment protocol

1. Qualification of the patient for liver resection or transplantation. Assessment of patients at an oncology consultation.
2. Obtaining informed consent to participate in the study.
3. Randomization of patients in a 2:1 ratio by drawing a code indicating ctDNA testing (control group - without ctDNA testing)

3. Assessment of the patient immediately before surgery.

a. Physical and subjective examination. i. Assessment of quality of life using the Polish version of the EORTC QLQ-C30 form b. Performing laboratory and imaging tests in accordance with local protocol. i. Biochemical tests ii. Imaging tests 4. Collecting 10ml of blood for gDNA and ctDNA testing along with routine preoperative blood collection.

5. Surgery 6. Liver resection or orthotopic liver transplantation from a deceased donor. 8. Monitoring the patient in the surgical intensive care unit. 9. Monitoring the patient in the general room at the Department of General, Transplantation and Liver Surgery.

10. Discharge of the patient home and completion of surgical treatment. 11. Monitoring the patient in the general room of the Hepatology Clinic in the case of transplantation or in the Polyclinic in the case of liver resection.

12. Transplantation/surgical outpatient clinic: Assessment on the 30th day (with a deviation of 2-3 days) after surgery in terms of the occurrence of postoperative complications, assessment general examination of the patient and 2 taking a blood sample for ctDNA testing.

13. Transplant/surgical outpatient clinic: Assessment in the 6th month (with a deviation of a few days) after surgery in terms of the patient's general condition and possible recurrence cancer process, taking a third blood sample for ctDNA testing. 14. Transplant/surgical outpatient clinic: Monitoring the cancer process and assessing patients one year after resection/transplantation.

16. End of the observation period of patients 12 months after the last collection

Inclusion Criteria:

• age 18-75 years of both sexes;
• patients with synchronous or metachronous metastases of colorectal cancer limited to the liver after complete removal of the primary lesion from the intestine qualified for liver resection or transplantation;
• or patients with resectable or unresectable HCC scheduled for liver resection or transplantation
• no history of other cancers;
• negative virological status in the case of mCRC;
• In the case of mCRC - patient after any type of liver surgery (staged, ALPPS, multi-site resection)
• Patient with or without neoadjuvant chemotherapy compatible with established adjuvant therapy

Exclusion Criteria:

• age under 18 and over 75;
• pregnancy
• patients with extrahepatic metastases visible in imaging studies;
• metabolic and autoimmune diseases or chronic immunosuppressive treatment other than in the group of patients after liver transplantation due to HCC;
• positive virological status, excluding the group of patients with HCC;
• history of other cancer;
• Chronic steroid therapy and diagnosed active autoimmune diseases
• Patient after radiotherapy
• Patient participating in other clinical trials of oncological and non-oncological drugs
• Patients legally incapacitated