Рак печени: причины, факторы риска и современные тенденции.

Hepatocellular carcinoma (HCC HCC is the third leading cause of cancer related deaths worldwide. The development of HCC is attributed to fibrosis and cirrhosis, which occur in the setting of chronic liver injury and inflammation. The latter being closely linked to chronic viral hepatitis infection (hepatitis B or C) or exposure to toxins such as alcohol, aflatoxin, or pyrrolizidine alkaloids. Certain diseases, such as hemochromatosis and alpha 1 antitrypsin deficiency, markedly increase the risk of developing HCC. Metabolic syndrome and NASH are also increasingly recognized as risk factors for HCC. As with any cancer, the treatment and prognosis of HCC vary depending on the specifics of tumor histology, size, how far the cancer has spread, and overall health. The vast majority of HCC cases and the lowest survival rates after treatment occur in Asia and sub Saharan Africa, in countries where hepatitis B infection is endemic and many are infected from birth. The incidence of HCC in the United States and other developing countries is increasing due to an increase in hepatitis C virus infections. It is more than three times as common in males as in females, for unknown reasons.

Hepatocellular carcinoma, like any other cancer, develops when epigenetic alterations and mutations affecting the cellular machinery cause the cell to replicate at a higher rate and/or result in the cell avoiding apoptosis. In particular, chronic infections of hepatitis B and/or C can aid the development of hepatocellular carcinoma by repeatedly causing the body's own immune system to attack the liver cells, some of which are infected by the virus, others merely bystanders. Activated immune system inflammatory cells release free radicals, such as reactive oxygen species and nitric oxide reactive species, which in turn can cause DNA damage and lead to carcinogenic gene mutations. Reactive oxygen species also cause epigenetic alterations at the sites of DNA repair. While this constant cycle of damage followed by repair can lead to mistakes during repair, which in turn lead to carcinogenesis, this hypothesis is more applicable, at present, to hepatitis C. Chronic hepatitis C causes HCC through the stage of cirrhosis. In chronic hepatitis B, however, the integration of the viral genome into infected cells can directly induce a noncirrhotic liver to develop HCC. Alternatively, repeated consumption of large amounts of ethanol can have a similar effect. The toxin aflatoxin from certain Aspergillus species of fungi is a carcinogen and aids carcinogenesis of hepatocellular cancer by building up in the liver. The combined high prevalence of rates of aflatoxin and hepatitis B in settings such as China and West Africa has led to relatively high rates of hepatocellular carcinoma in these regions. Other viral hepatitides such as hepatitis A have no potential to become a chronic infection, thus are not related to HCC. Elevated levels of AFP are associated with active HCC disease, though their reliability can be inconsistent. At levels >20, sensitivity is 41–65% and specificity is 80–94%. However, at levels >200, sensitivity is 31 and specificity is 99%. On ultrasound, HCC often appears as a small hypoechoic lesion with poorly defined margins and coarse, irregular internal echoes. When the tumor grows, it can sometimes appear heterogeneous with fibrosis, fatty change, and calcifications. This heterogeneity can look similar to cirrhosis and the surrounding liver parenchyma. A systematic review found that the sensitivity was 60% (95% CI 44–76%) and specificity was 97% (95% CI 95–98%) compared with pathologic examination of an explanted or resected liver as the reference standard. The sensitivity increases to 79% with AFP correlation. Controversy remains as to the most effective screening protocols. For example, while some data support decreased mortality related to screening people with hepatitis B infection, the AASLD notes, “There are no randomized trials [for screening] in Western populations with cirrhosis secondary to chronic hepatitis C or fatty liver disease, and thus there is some controversy surrounding whether surveillance truly leads to a reduction in mortality in this population of patients with cirrhosis.” evaluation requires imaging of the liver by CT or MRI scans. Optimally, these scans are performed with intravenous contrast in multiple phases of hepatic perfusion to improve detection and accurate classification of any liver lesions by the interpreting radiologist. Due to the characteristic blood flow pattern of HCC tumors, a specific perfusion pattern of any detected liver lesion may conclusively detect an HCC tumor. Alternatively, the scan may detect an indeterminate lesion and further evaluation may be performed by obtaining a physical sample of the lesion.

Since hepatitis B and C are some of the main causes of hepatocellular carcinoma, prevention of infection is key to then prevent HCC. Thus, childhood vaccination against hepatitis B may reduce the risk of liver cancer in the future. In the case of patients with cirrhosis, alcohol consumption is to be avoided. Also, screening for hemochromatosis may be beneficial for some patients. Whether screening those with chronic liver disease for HCC improves outcomes is unclear.

Surgical removal of the tumor is associated with better cancer prognosis, but only 5–15% of patients are suitable for surgical resection due to the extent of disease or poor liver function. Surgery is only considered if the entire tumor can be safely removed while preserving sufficient functional liver to maintain normal physiology. Thus, preoperative imaging assessment is critical to determine both the extent of HCC and to estimate the amount of residual liver remaining after surgery. To maintain liver function, residual liver volume should exceed 25% of total liver volume in a noncirrhotic liver, greater than 40% in a cirrhotic liver. Surgery on diseased or cirrhotic livers is generally associated with higher morbidity and mortality. The overall recurrence rate after resection is 50–60%. The Singapore Liver Cancer Recurrence score can be used to estimate risk of recurrence after surgery.

Liver transplantation, replacing the diseased liver with a cadaveric or a living donor liver, plays an increasing role in treatment of HCC. Although outcomes following liver transplant were initially poor (20%–36% survival rate), Studies from the late 2000s obtained higher survival rates ranging from 67% to 91%. The risks of liver transplantation extend beyond risk of the procedure itself. The immunosuppressive medication required after surgery to prevent rejection of the donor liver also impairs the body's natural ability to combat dysfunctional cells. If the tumor has spread undetected outside the liver before the transplant, the medication effectively increases the rate of disease progression and decreases survival. With this in mind, liver transplant "can be a curative approach for patients with advanced HCC without extrahepatic metastasis". In fact, among patients with compensated cirrhosis, transplantation is not associated with improved survival compared to hepatectomy, but instead is significantly more expensive. Patient selection is considered a major key for success.

Radiofrequency ablation (RFA) uses high frequency radio waves to destroy tumor by local heating. The electrodes are inserted into the liver tumor under ultrasound image guidance using percutaneous, laparoscopic or open surgical approach. It is suitable for small tumors (<5 cm). RFA has the best outcomes in patients with a solitary tumor less than 4 cm. Since it is a local treatment and has minimal effect on normal healthy tissue, it can be repeated multiple times. Survival is better for those with smaller tumors. In one study, In one series of 302 patients, the three year survival rates for lesions >5 cm, 2.1 to 5 cm, and ≤2 cm were 59, 74, and 91%, respectively. A large randomized trial comparing surgical resection and RFA for small HCC showed similar four year survival and less morbidities for patients treated with RFA. Cryoablation is a technique used to destroy tissue using cold temperature. The tumor is not removed and the destroyed cancer is left to be reabsorbed by the body. Initial results in properly selected patients with unresectable liver tumors are equivalent to those of resection. Cryosurgery involves the placement of a stainless steel probe into the center of the tumor. Liquid nitrogen is circulated through the end of this device. The tumor and a half inch margin of normal liver are frozen to −190 °C for 15 minutes, which is lethal to all tissues. The area is thawed for 10 minutes and then refrozen to −190 °C for another 15 minutes. After the tumor has thawed, the probe is removed, bleeding is controlled, and the procedure is complete. The patient spends the first postoperative night in the intensive care unit and typically is discharged in 3–5 days. Proper selection of patients and attention to detail in performing the cryosurgical procedure are mandatory to achieve good results and outcomes. Frequently, cryosurgery is used in conjunction with liver resection, as some of the tumors are removed while others are treated with cryosurgery. Percutaneous ethanol injection is well tolerated, with high RR in small (<3 cm) solitary tumors; as of 2005, no randomized trial has comparing resection to percutaneous treatments; recurrence rates are similar to those for postresection. However, a comparative study found that local therapy can achieve a 5 year survival rate around 60% for patients with small HCC.

Transcatheter arterial chemoembolization (TACE) is performed for unresectable tumors or as a temporary treatment while waiting for liver transplant ("bridge to transplant"). TACE is done by injecting an antineoplastic drug (e. g. cisplatin) mixed with a radio opaque contrast (e. g. Lipiodol) and an embolic agent (e. g. Gelfoam) into the right or left hepatic artery via the groin artery. The goal of the procedure is to restrict the tumor's vascular supply while supplying a targeted chemotherapeutic agent. TACE has been shown to increase survival and to downstage HCC in patients who exceed the Milan criteria for liver transplant. Patients who undergo the procedure are followed with CT scans and may need additional TACE procedures if the tumor persists. As of 2005, multiple trials show objective tumor responses and slowed tumor progression, but questionable survival benefit compared to supportive care; greatest benefit is seen in people with preserved liver function, absence of vascular invasion, and smallest tumors. TACE is not suitable for big tumors (>8 cm), the presence of portal vein thrombus, tumors with a portal systemic shunt, and patients with poor liver function. Selective internal radiation therapy (SIRT) can be used to destroy the tumor from within (thus minimizing exposure to healthy tissue). Similar to TACE, this is a procedure in which an interventional radiologist selectively injects the artery or arteries supplying the tumor with a chemotherapeutic agent. The agent is typically Yttrium 90 (Y 90) incorporated into embolic microspheres that lodge in the tumor vasculature, causing ischemia and delivering their radiation dose directly to the lesion. This technique allows for a higher, local dose of radiation to be delivered directly to the tumor while sparing normal healthy tissue. While not curative, patients have increased survival. No studies have been done to compare whether SIRT is superior to TACE in terms of survival outcomes, although retrospective studies suggest similar efficacy. Two products are available, SIR Spheres and TheraSphere. The latter is an FDA approved treatment for primary liver cancer (HCC) which has been shown in clinical trials to increase the survival rate of low risk patients. SIR Spheres are FDA approved for the treatment of metastatic colorectal cancer, but outside the US, SIR Spheres are approved for the treatment of any nonresectable liver cancer including primary liver cancer.

The role of radiotherapy in the treatment of hepatocellular carcinoma has evolved as technological advancements in treatment delivery and imaging have provided a means for safe and effective radiotherapy delivery in a wide spectrum of HCC patients. In metastatic cases, radiotherapy can be used for palliative care. Proton therapy for unresectable hepatocellular carcinoma was associated with improved survival relative to photon based radiation therapy which may be driven by decreased incidence of post treatment liver decompensation and a number of randomized controlled trials are currently ongoing.

In disease which has spread beyond the liver, systemic therapy may be a consideration. In 2007, Sorafenib, an oral multikinase inhibitor, was the first systemic agent approved for first line treatment of advanced HCC. Trials have found modest improvement in overall survival: 10.7 months vs 7.9 months and 6.5 months vs 4.2 months. A host of additional targeted therapies and immune checkpoint inhibitors have been found to be effective against this disease. For instance, in the recent phase III trial IMBrave 150, the combination of atezolizumab and bevacizumab was found to improve both overall and progression free survival compared to sorafenib alone. Tremelimumab (Imjudo) was approved for medical use in the United States in October 2022.

Portal vein embolization (PVE): This technique is sometimes used to increase the volume of healthy liver, in order to improve chances of survival following surgical removal of diseased liver. For example, embolization of the right main portal vein would result in compensatory hypertrophy of the left lobe, which may qualify the patient for a partial hepatectomy. Embolization is performed by an interventional radiologist using a percutaneous transhepatic approach. This procedure can also serve as a bridge to transplant. High intensity focused ultrasound (HIFU) (as opposed to diagnostic ultrasound) is an experimental technique which uses high powered ultrasound waves to destroy tumor tissue. A systematic review assessed 12 articles involving a total of 318 patients with hepatocellular carcinoma treated with Yttrium 90 radioembolization. Excluding a study of only one patient, post treatment CT evaluation of the tumor showed a response ranging from 29 to 100% of patients evaluated, with all but two studies showing a response of 71% or greater.

The usual outcome is poor because only 10–20% of hepatocellular carcinomas can be removed completely using surgery. If the cancer cannot be completely removed, the disease is usually deadly within 3 to 6 months. This is partially due to late presentation with tumors, but also the lack of medical expertise and facilities in the regions with high HCC prevalence. However, survival can vary, and occasionally people survive much longer than 6 months. The prognosis for metastatic or unresectable HCC has improved due to the approval of Sorafenib (Nexavar®) for advanced HCC.

HCC is one of the most common tumors worldwide. The epidemiology of HCC exhibits two main patterns, one in North America and Western Europe and another in non Western countries, such as those in sub Saharan Africa, Central and Southeast Asia, and the Amazon basin. Males are affected more than females usually, and it is most common between the ages of 30 and 50, about half of them in China.

In some parts of the world, such as sub Saharan Africa and Southeast Asia, HCC is the most common cancer, generally affecting men more than women, and with an age of onset between the late teens and 30s.

The most common malignant tumors in the liver represent metastases (spread) from tumors which originate elsewhere in the body. As screening programs are in place for high risk persons with chronic liver disease, HCC is often discovered much earlier in Western countries than in developing regions such as sub Saharan Africa. Acute and chronic hepatic porphyrias (acute intermittent porphyria, porphyria cutanea tarda, hereditary coproporphyria, variegate porphyria) and tyrosinemia type I are risk factors for hepatocellular carcinoma. The diagnosis of an acute hepatic porphyria (AIP, HCP, VP) should be sought in patients with HCC without typical risk factors of hepatitis B or C, alcoholic liver cirrhosis, or hemochromatosis. Both active and latent genetic carriers of acute hepatic porphyrias
are at risk for this cancer, although latent genetic carriers have developed the cancer at a later age than those with classic symptoms. Patients with acute hepatic porphyrias should be monitored for HCC. The incidence of HCC is relatively lower in the Western Hemisphere than in Eastern Asia. However, despite the statistics being low, the diagnosis of HCC has increased since the 1980s and it is continuing to increase, making it one of the rising causes of death due to cancer. The common risk factor for HCC is hepatitis C, along with other health issues.

Mipsagargin (G 202), has orphan drug designation as a treatment during chemotherapy for HCC. It is a thapsigargin based prodrug with cytotoxic activity used to reduce blood flow to the tumor during treatment. Results from Phase 2 trial recommended G 202 as a first in class PSMA targeted prodrug and that it move to clinical trials. Current research includes the search for the genes that are disregulated in HCC, antiheparanase antibodies, protein markers, non coding RNAs (such as TUC338) and other predictive biomarkers. As similar research is yielding results in various other malignant diseases, it is hoped that identifying the aberrant genes and the resultant proteins could lead to the identification of pharmacological interventions for HCC. The development of three dimensional culture methods provides a new approach for preclinical studies of cancer therapy using patient derived organoids. These miniaturized organoid 'avatars' of a patient's tumor recapitulate several features of the original tumor, rendering them an attractive model for drug sensitivity testing and precision medicine for HCC and other types of primary liver cancer. Furthermore, HCC occurs in patients with liver disease. A biomarker named six miRNA signature allows effective treatment of patients with HCC and is able to predict its recurrence in the liver. A prospective study found that increased hepatocellular cancer risk is associated with higher levels of major circulating bile acids that were measured in people several years prior to tumor diagnosis. In another study using a mouse model, it was found that dysregulated hepatic bile acids collaboratively promote liver carcinogenesis.

JX 594, an oncolytic virus, has orphan drug designation for this condition and is undergoing clinical trials. Hepcortespenlisimut L (Hepko V5), an oral cancer vaccine, also has US FDA orphan drug designation for HCC. Immunitor Inc. completed a Phase II trial, published in 2017. A randomized trial of people with advanced HCC showed no benefit for the combination of everolimus and pasireotide.