Liver Cancer Screening - A Lifesaving Method

Introduction

The liver is one of the important parts of the digestive system. It helps in the metabolic process of the human body and helps maintain the balance among various chemicals in the body. Thus, any liver disease can disrupt the balance of the human body. Liver cancer is a very dangerous disorder with a high mortality rate. Proper screening and diagnostic tests can save the life of liver cancer patients.

What Is Liver Cancer?

Cancerous changes in the cells of the liver are known as liver cancer. Liver cancer is the sixth most prevalent cancer in the world. Around 80000 people are diagnosed with liver cancer each year. The global burden of liver cancer has recently increased by about 50 percent. The mortality rate of liver cancer is very high. Among cancerous diseases, the mortality rate of liver cancer is the second highest. The five-year survival rate of localized liver cancer is only 36 percent, and in severe cases, it can be as low as 13 percent. The risk factors for liver cancer are:

1. Hepatitis B Virus: This virus belongs to the Hepadnaviridae family. Such viruses are found in ground squirrels, tree squirrels, and woodchucks. Around 1.5 million people globally are affected by such viruses every year. Horizontal transfer of this virus occurs through sexual contact or mucosal contact. Unprotected sex, semen, saliva, blood, and vaginal secretions are responsible for such transmission. The use of contaminated needles is also responsible for virus transmission. In the case of vertical transmission, the transmission occurs from the mother to the fetus.

2. Hepatitis C Virus: Hepatitis C is a single-stranded RNA (ribonucleic acid) virus. It belongs to the family of Flaviviridae and the genus Hepacivirus. The transmission of the Hepatitis C virus mainly occurs through the blood and blood products. Blood transfusion is one of the key causes of such infections. Apart from this, the use of contaminated instruments in medical surgical procedures may cause transmission of such infections. The infection may be transmitted to the child via the mother. Blood contamination during sexual contact, especially those who have multiple sexual contacts, increases the incidence of transmission of such viruses.

3. Aflatoxins: Aflatoxins are metabolites produced by the fungal species Aspergillus flavus and A. parasiticus. Exposure to this carcinogenic toxin occurs during cavitation and crop harvesting.

4. Alcohol: Excessive alcohol intake is responsible for fatty degeneration of the liver cells and decreased blood supply to the liver cells. Ultimately, this causes fatty liver and liver cirrhosis. Acetaldehyde produced from the liver acts as a carcinogen.

5. Infection: Parasitic infections are responsible for liver cancer. Parasites like Opisthorchis viverrini and Clonorchis sinensis are linked to liver cancer. The spread of such practices occurs through eating snails, raw fish, and Cyprinidae fish.

6. Genetic Factors: Mutation of genes like TP53, RB1, CCNA2, CCNE1, PTEN, ARID1A, ARID2, and RPS6KA3 is responsible for the alteration of cellular pathways and causes liver cancer.

What Are the Types of Liver Cancer?

The two most common types of liver cancer are:

1) Metastatic or Secondary Liver Cancer: This type of cancer occurs due to the metastasis of the cancerous cells from other organs. Around 25 percent of cases of liver metastasis can be seen. The rich circulation of the liver is the primary cause of this. The liver receives blood supply from many sources like the hepatic artery, pulmonary circulation, and venous drainage from various organs. The causative factors for secondary liver cancer are:

1. Breast cancer.

2. Bowel cancer.

3. Gastric cancer.

4. Cancer of the esophagus.

5. Melanoma.

6. Neuroendocrine tumors.

2) Primary Liver Cancer: In this case, liver cancer is caused by carcinomatous changes in the liver. Such types of liver cancer can be divided into two types. These are:

1. Hepatocellular Carcinoma: This type of cancer is known as hepatoma. In this case, cancer changes can be seen in hepatocytes. Such liver diseases arise from chronic liver disease. Patients with liver cirrhosis can be affected by this type of cancer. Infectious conditions like hepatitis B, and C, and chronic alcoholism are potential risk factors.

2. Fibrolamellar Carcinoma: This is a rare type of liver cancer that mainly affects persons under 40 years of age. This type of cancer is seen in less than 1 percent of cases of liver carcinoma. Liver cirrhosis is the primary cause of this type of liver cancer. Big cancerous cells with the presence of eosinophilic cytoplasms are the hallmark features of this type of cancer.

3. Cholangiocarcinoma Carcinoma: This is also called the cancer of the bile duct. The bile duct is a network of small capillaries that connects the liver, gallbladder, and small intestine. The exact risk factors for these types of cancer are not known, but this is linked to hepatobiliary disease, genetic disorders, toxic exposures, and infectious diseases. This is seen in around 13 to 15 percent of cases. In this condition, cancerous changes are seen in intraepithelial cells or intraductal papillary cells.

What Are the Screening Methods?

The screening of liver cancer can be done through the identification of serological factors and imaging methods. These tests are:

1. Alpha-Fetoprotein (AFP) Biomarker Testing: Alpha-fetoprotein (AFP) is a glycoprotein produced by the fetal liver. But the level of this biomarker is elevated in liver cancer cases specifically in hepatocellular liver cancer. Also, the level of this biomarker has prognostic values which are used to determine the prognosis of the diseases, the prognosis of the treatment, and the size of the tumor.

2. Des-Gamma-Carboxy Prothrombin (Dcp) Biomarkers: In normal conditions, liver cells produce anticoagulant-like prothrombin with the help of vitamin K. but in cases of hepatocellular cancer vitamin K is not present. In such cases, des-gamma-carboxy prothrombin (DCP) is produced as a precursor of the prothrombin. The levels of DCP remain high in the advanced stages of hepatocellular liver cancer. A higher DCP level also signifies the large size of the liver tumor and the involvement of the lymph nodes.

3. Ultrasound Imaging: In this procedure, ultrasound sound waves are projected toward the organs through a transducer. These soundwaves bounce off the organs like an echo and are captured by the transducer, which then processes these data from an image of the object. In the case of liver cancer diagnosis contrast medium is used for proper visualization of underlying structures. This is known as contrast-enhanced ultrasound (CEUS). The basket pattern of blood flow is the key finding in hepatocellular liver cancer. In cholangiocarcinomas, biliary duct dilatation along with hyperechoic mass can be observed.

4. Computer-Based Tomography (CT): This is a radiation-based imaging procedure. Through this procedure, entire imaging of the liver can be done within 10 seconds. The variable density of the liver tissue due to the presence of different ions can affect the quality of CT imaging. Hepatocellular carcinoma appears as a well-defined fibrous structure with the presence of a mosaic pattern. For the detection of

5. Magnetic Resonance Imaging (MRI): In this technique, radio waves and magnetic fields are used to construct images of the internal organs. Soft tissue contrast and multiplanar analysis of the carcinoma can be diagnosed through this process. The sensitivity of MRI imaging in detecting liver cancer is very high. Gadolinium chelates are used as an intravenous contrast medium for MRI.

6. Liver Biopsy: It is an invasive method of detecting liver cancer. The ultrasound-guided biopsy procedure is a fast and cost-effective way of determining the presence of liver cancer. In cases of hepatocellular cancer transvenous method of liver biopsy is followed. Bleeding and non-hepatic organ puncture are the potential side effects of this technique.

7. Liquid Biopsy (LB): This is a new procedure in which the blood sample is collected and proteomic assessment of a wide variety of tumor-derived molecules such as circulating tumor cells circulating tumor DNA (ctDNA), tumor-derived extracellular vesicles (EVs) is done. This procedure helps to eliminate potential complexities of biopsy and radiological techniques. Molecular assessment helps to pinpoint the exact cancer disorder and its progression.

Conclusion

Liver cancer is one of the most common cancers worldwide. The mortality rate in such cases is very high. The cancerous growth of the liver cells occurs either through metastasis or through malignant changes in the hepatocytes. Early detection of the cancer can improve the life expectancy of the patient. Diagnostic tests like the detection of biomarkers, image analysis, and biopsy procedures are helpful in the cancer screening process.