Nucleos(t)ide analogues and Hepatitis B virus-related hepatocellular carcinoma: A literature review.

Hepatitis B virus is mainly considered to cause hepatocellular carcinoma which is the fourth leading cause of cancer-related mortality worldwide. Treatment of Hepatitis B virus with nucleos(t)ide analogues can decrease the progression of the disease and subsequently decreases the incidence of hepatocellular carcinoma. In this review, we have discussed the different classes of nucleos(t)ide analogues used in the treatment of Hepatitis B virus and their relationship with the development of hepatocellular carcinoma. Furthermore, we discussed the effect of treatment of Hepatitis B virus with Nucleoside analogues (NAs) before, during and after surgery, chemoembolization, radiofrequency ablation, and chemotherapy for the treatment of hepatocellular carcinoma.

Introduction

Hepatocellular carcinoma (HCC) is the fourth leading cause of cancer-related mortality worldwide.[1] It is the fifth most common cancer diagnosed among adult men and the ninth most common cancer diagnosed among women.[1] Between 1990 and 2015 the incidence of liver cancer has increased by 75%.[2] Among all risk factors of HCC, Hepatitis B virus (HBV) is believed to be the leading cause of incident cases and mortality of HCC globally.[2,3]

HBV is a double-stranded DNA virus that can be transmitted perinatally from the mother to her child, through unprotected sexual intercourse, or through blood products (e.g. needle sticks).[4,5] After infection, the HBV transfers its DNA into the host’s hepatocyte nucleus and starts using the organoids of the hepatocyte nucleus for its replication.[6] The random integration of the virus genome into the host’s genome is considered the initiating incident for HCC development.[6] The nucleos(t)ide analogue drugs (NUCs) have been developed to block the HBV DVA polymerase enzyme, thus inhibiting the virus replication and further infection of the neighbor cells.[7] However, the protective mechanism of these drugs against the development of HCC is still questionable. The aim of the current study is to review the literature regarding whether treatment of HBV using NUCs helps prevent the development of HCC or not.

Lamivudine risk of HCC after treatment with nucleos(t)ide analogues

Lamivudine therapy

Data from a multicenter randomized controlled trial (RCT) have shown that treatment with lamivudine for a median duration of 32.4 months has decreased the incidence of HCC development compared to placebo 3.9% in lamivudine group versus 7.4% in the placebo group with an adjusted HR: 0.49 (0.25–0.99).[8] Even in patients with cirrhosis, lamivudine therapy has been shown to decrease the risk of HCC as shown in a retrospective analysis for 238 patients; the incidence of HCC in patients treated with lamivudine was 9.8% compared to 25% in the control group. In addition, the mortality was lower in patients treated with lamivudine compared to the control group.[9] The optimal duration of lamivudine therapy has become a matter of debate, and a study conducted by Kwon et al. has suggested that treatment for more than five years in patients who do not develop YMDD mutations may continue treatment for over five years until loss of HBV surface antigen (HBsAg).[10] However, the maintained viral response achieved by lamivudine treatment for more than five years did not show a decrease in the incidence of HCC.[11] Nevertheless, about 43% of the included patients had liver cirrhosis at baseline which is known to be an independent risk factor for HCC development even in lamivudine-treated patients (OR = 12.1, 95% confidence interval (CI) 1.39 to 106.2).[12] On the other hand, Eun et al. have found that sustained viral suppression with long-term lamivudine therapy has decreased the incidence of HCC.[13] During treatment with lamivudine, resistance can develop which may be due to mutations in the viral DNA.[14] In this population, treatment with adefovir has been tried as an add-on therapy which showed a great success.[15] However, caution should be taken in patients with YIDD mutations and HBeAg-positive patients.[16,17] However, in patients with HBeAg negative, lamivudine has been shown to decrease the Child-Pugh scores in the first three years of follow-up. In addition, after lamivudine therapy, the incidence of HCC in cirrhotic patients with HBeAg negative was comparable to non-cirrhotic patients (13.2%).[18]

Impact on liver-related mortality

Lamivudine treatment has been shown to decrease the liver-related mortality in patients with HBV even in patients with co-infection with human immune deficiency virus (HIV).[19] Effective viral suppression has shown to reduce the risk of HCC development with a 10-year cumulative incidence of 15.73%.[20] However, baseline cirrhosis is known to be a significant risk factor for HCC with a 10-year incidence of 43.16% in cirrhotic patients versus 7.05% in non-cirrhotic patients.[20] Nevertheless, the achievement of viral suppression has decreased the incidence of HCC in cirrhotic patients (10-year incidence of 27.78% in cirrhotic patients who achieved viral suppression compared to 62.24% in cirrhotic patients who did not achieve viral suppression).[20] On the other hand, data from a larger sample size have shown that serological clearance has been only beneficial to patients without cirrhosis.[21]

Adefovir therapy

Adefovir is considered an option for patients with lamivudine resistance. Although adefovir alone therapy has been shown to be an effective treatment for HBV patients and its long-term use has been shown to decrease the fibrosis score, the emergence of resistance with its long-term use is a major limitation.[22] The combination between adefovir and lamivudine in patients with lamivudine resistance chronic HBV has shown a great success and lower mutations rate that might lead to adefovir resistance. In addition, the three-year follow-up has shown a 12% risk of developing HCC while 73% of the included patients had cirrhosis at baseline.[23]

Entecavir or tenofovir therapy

Entecavir treatment has been shown to decrease the incidence of HCC compared to non-treatment. The five-year incidence rate was 3.7% in entecavir group compared to 13.7% in the no-treatment group (adjusted HR: 0.37; 95% CI; (0.15–0.91)).[24] However, a retrospective analysis of 875 chronic HBV patients who were treated with entecavir monotherapy has shown that 43% of the treated patients did not achieve a maintained virological remission (MVR) (persistently undetectable HBV DNA (<12 IU/mL) and they were at a higher risk of developing HCC especially in patients with cirrhosis.[25] This finding might raise the concern to change the entecavir therapy if the patient did not achieve MVR during the treatment. For patients with cirrhosis, treatment with entecavir has resulted in a decrease in the incidence of HCC. However, the level of compensation affected the incidence of HCC (2.2% in compensated group versus 13.7% in the decompensated group).[26] Age > 50 years old, male sex, high serum level of Procollagen III N-terminal peptide, and no virological response after 12 months of treatment were recognized as independent risk factors for developing HCC in patients with HBV-related cirrhosis treated with entecavir.[27] Nevertheless, a subgroup analysis according to the level of decompensation has revealed that no virological response after 12 months of treatment with entecavir is an independent risk factor for HCC development in decompensated patients but not in compensated cirrhosis patients.[27] Follow-up with serum alanine aminotransferase (ALT) at 6 months and 12 months is advised during treatment with entecavir . Normal ALT at 6 months and 12 months was found to have the least risk factor for the development of HCC.[28] In addition, surveillance using serum alpha-fetoprotein was advised. A cut off value of 13 ng/ml was found to have a positive predictive value of 77.8% and a negative predictive value of 96.1% for the development of HCC in patients treated with entecavir.[29,30]

Entecavir as a second line rescue treatment after prior NUCs resistance has shown success. In addition, the virological clearance in these cases after treatment with entecavir was found to be a protective factor against the development of HCC.[31]

Data from an international RCT have shown that there were no differences between entecavir use and any other NUCs use on the incidence of HCC after follow-up for 10 years (0.87 (0.727–1.032)).[32] This finding was supported by data from retrospective studies.[33] However, in the Chinese population, tenofovir has been shown to be superior to entecavir in the prevention of HCC development (adjusted HR: 0.39; 95% CI; (0.18–0.84)).[34] Data from a recently published meta-analysis have shown that patients treated with tenofovir had a lower incidence of HCC compared to patients treated with entecavir (rate ratio: 0.66 (0.49–0.89)).[35] Tenofovir has been shown to be effective as a second line rescue therapy after lamivudine–adefovir failure.[36] Nevertheless, five (8%) patients with cirrhosis developed HCC after a median of 26.5 months of treatment with tenofovir after being treated with lamivudine–adefovir.[36]

Telbivudine therapy

The results of RCTs have shown that telbivudine was superior to lamivudine in the treatment of patients with chronic HBV regardless of HBeAg status.[37-39] In addition, results from several RCTs have shown the superiority of telbivudine over other NUCs such as entecavir[40,41] and adefovir.[42] However, in 2013, Tsai et al. found that the cumulative incidence of HCC development in patients treated with telbivudine was 2.5% and 4.1% at two and three years, respectively which was not statistically different from the results of patients treated with entecavir (3.1% and 7.5% at two and three years respectively; P = 0.565).[43] Nevertheless, the kidney function should be taken into consideration while choosing between the NUCs. Of note, telbivudine was found to be more effective in the prevention of nephrotoxicity.[44]

Interferon therapy

Data from an open-label RCT have shown that use of interferon-alpha with the NUCs for 96 weeks has resulted in increased clearance of HBsAg compared to NUCs alone. However, grade 3 and 4 adverse events were more frequently reported in the interferon group.[45] Moreover, data from retrospective studies have shown that interferon treatment is superior to NUCs in the suppression of viral load, HbsAg clearance and in the prevention of HCC.[46,47] Although they did not conduct a subgroup analysis according to the type of NUCs used, about 60% of patients in the NUCs group received entecavir only.[46] In a five-year observational study, the five-year cumulative incidence rate for HCC was lower in patients treated with interferon compared to entecavir.[48]

Putting all together

Data concerning the efficacy of different NUCs in reducing the risk of HCC are summirized in Table 1.

Table 1.

Data concerning the efficacy of different NUCs in reducing the risk of HCC.

	Number of studies	Effect estimate (RR)	Heterogeneity level
Incidence of HCC in NUCs-treated chronic HBV patients
ETV versus LAM	7	0.45 (0.3–0.67)	I2 = 43%
ETV versus LdT	3	0.72 (0.24–2.14)	I2 = 0%
ETV versus TDF	8	1.52 (0.95–2.44)	I2 = 40%
Biochemical response
ETV versus LAM	1	1.32 (1.11–1.56)	NA
ETV versus LdT	1	1.09 (0.96–1.23)	NA
ETV versus TDF	2	1.06 (0.93–1.20)	I2 = 35%
Virological response
ETV versus LAM	2	1.15 (1.03–1.29)	I2 = 30%
ETV versus LdT	2	1.37 (1.16–1.62)	I2 = 50%
ETV versus TDF	3	0.95 (0.86–1.05)	I2 = 44%
HBeAg serological conversion
ETV versus LAM	1	1.01 (0.8–1.29)	NA
ETV versus LdT	2	1.36 (0.29–6.36)	I2 = 36%
ETV versus TDF	1	0.76 (0.42–1.4)	NA
Incidence of drug resistance
ETV versus LAM	4	0.03 (0.02–0.04)	I2 = 0%
ETV versus LdT	2	0.04 (0.01–0.22)	I2 = 0%
ETV versus TDF	1	0.94 (0.14–6.46)	NA
Risk of HCC in patients with CHB treated with NUCs + LC versus CHB treated with NUCs without LC
Wang et al., 2019	7	30.12 (1.79–506.24)	I2 = 22%

ETV: entecavir; TDF: tenofovir disoproxil fumarate; TAF: tenofovir alafenamide; LAM: lamivudine; ADV: adefovir dipivoxil; LdT: telbivudine; HCC: hepatocellular carcinoma; HBV: Hepatitis B virus; RR: risk ratio; HBeAg: Hepatitis B e-antigen; CHB: chronic Hepatitis B virus; LC: liver cirrhosis.

Biochemical response: normalization of the level of alanine aminotransferase as assessed by routine hepatic panel

Virological response: undetectable HBV DNA in an HBeAg-negative patient

Drug resistance: the reappearance of HBV DNA after a period of non-detectable HBV DNA.

Prediction of HCC after treatment with nucleos(t)ide analogues

Several studies have been conducted to study the best method of HCC surveillance in HBV patients who are treated with NUCs.[49] For example, elevated serum Mac-2-binding protein glycosylation isomer after 48 weeks of antiviral therapy was found to be a predictive factor for the development of HCC which might warrant more close follow-up of these patients’ population.[49] In these contexts, Hsu et al. developed a scoring system to predict the HCC occurrence in patients with HBV treated with NUCs. They found that there are four independent variables related to the risk which are cirrhosis, age, male gender and diabetes mellitus. They denoted to it with CAMD score[50] (Table 2). Patients with a score <8 have a three-year cumulative incidence for the development of HCC of 0.27% (95% CI 0.12–0.42%), compared to 2.40% (95% CI 2.03–2.78%), and 10.75% (95% CI 9.68–11.81%), in patients with a score of 8–13 and >13 respectively with AUC of 0.74 (95% CI) (0.71–0.76).[50,51] Similarly, several risk scores have been developed.[52-55]

Table 2.

CAMD scoring system for the prediction of HCC in HBV patients treated with antiviral therapy.

Variable	CAMD score
Cirrhosis
No cirrhosis	0
Cirrhosis with age <40 years	10
Cirrhosis with age ≥40 years	6
Age (years)
<40	0
40–49	5
50–59	8
≥60	10
Sex
Male	2
Female	0
Diabetes mellitus (DM)
No DM	0
Presence of DM	1

CAMD: cirrhosis, age, male sex and diabetes mellitus.

Role of nucleos(t)ide analogues after treatment of HCC

Prophylaxis after liver transplantation

After liver transplantation for HBV-related HCC, recurrence of HBV was associated with a 3.6 fold increase in the HCC recurrence.[56] In these cases, prophylaxis with HBV immunoglobulin is recommended.[57] However, data from several meta-analyses have revealed the benefits of adding lamivudine to the HBV immunoglobulin with regard to HBV, HCC recurrence and survival rates.[58-60] Nevertheless, adding adefovir to the HBV immunoglobulin was found to be superior to lamivudine plus HBV immunoglobulin.[61] In addition, lower doses of HBV immunoglobulin could be given in the first week after the liver transplantation when adefovir is used compared to lamivudine.[61] Accordingly, adefovir was suggested as a therapeutic option after recurrence of HBV after liver transplantation or when resistance to lamivudine develops.[62,63]

After curative resection

Data from an RCT have shown that for patients with low HBV–DNA levels, antiviral therapy has been shown to reduce the recurrence of HCC after curative resection.[64] The 1-, 3-, and 5-year recurrence-free survival rates for patients treated with antiviral therapy were 85.9%, 55.2%, and 52% compared to 80.6%, 40.9%, and 32.3%, in the control group. In addition, the antiviral treatment was found to be an independent protective factor for recurrence (the adjusted hazard ratio (HR) = 0.316, 95% CI 0.157–0.637; P = 0.001).[64] Moreover, antiviral treatment after hepatectomy for patients who had HBV-related HCC has been shown to decrease the viral reactivation. The incidence of HBV reactivation was found to be 2.5% in the patients who have been treated with antiviral therapy compared to 31.8% in untreated patients.[65] This finding was supported by two meta-analyses.[66-68] However, subgroup analysis revealed that the improvement in the overall survival and the progression-free survival has only been found in patients with high baseline HBV DNA (≥20,000 IU/mL).[68] Of note, long-term adefovir therapy was associated with better overall survival and disease-free survival than long-term therapy with telbivudine in patients who had hepatectomy for HBV-related HCC.[69] Regarding the short-term post-operative complications after curative resection, perioperative antiviral therapy was found to reduce the patients’ recovery time and the improvement of the liver function compared to non-treatment groups.[70] The improvement of liver function and the progression-free survival after curative resection for HCC was found to be more likely in patients with HCC less than 3 cm in size.[71]

After chemoembolization

Lamivudine was found to decrease the HBV reactivation during chemoembolization. In an RCT, the HBV reactivation rate in the lamivudine group was 2.8% compared to 29.7% in the control group (P = 0.002).[72] On multivariate regression analysis, the baseline HBV DNA level of more than 104 copies/mL was the only predictor for reactivation.[72] Similarly, entecavir prophylactic therapy was found to decrease HBV reactivation with chemoembolization therapy.[73,74] However, females, HBeAg positive patients, number of tumors more than 3 and patients with Eastern Cooperative Oncology Group (ECOG) performance status 2 were found to be at higher risk for developing reactivation without treatment.[73,75] Regarding survival after chemoembolization therapy, NUCs therapy was found to improve the 1-, 3-, and 5-year survival rates compared to non-treatment groups.[76-78]

After radiofrequency ablation

Treatment with NUCs has shown to reduce the two-year recurrence rate compared to the non-treated group (1.8%; 95% CI: 32.9–50.6 vs. 54.3%; 95% CI: 48.0–60.6; modified log-rank test: P < 0.05).[79] In multivariate cox proportional HR, the antiviral therapy was the only protective factor against recurrence (HR: 0.69; 95% CI [0.5–0.95]).[79]

With multikinase inhibitors

In patients treated with sorafenib, concurrent administration of antiviral therapy improved the overall survival compared to the non-treated group (16.47 months vs. 13.10 months, P = 0.03).[80] The benefit in the overall survival was noted to be more in patients with Barcelona Clinic Liver Cancer (BCLC) stage C and patients with higher HBV DNA level at baseline.[80]

Conclusion

Although we have tried to provide an extensive overview of this very broad topic, we did not pool the results of the studies that we discussed. Nevertheless, the use of NUCs in patients with HBV seems to be protective against the development of HCC. Further studies are needed to provide more information about an individualized selection of the NUCs based on the patients’ characteristics.