Long-term outcomes of entecavir monotherapy for chronic hepatitis B after liver transplantation: Results up to 8 years

ANTIVIRAL PROPHYLAXIS

Since late 2007, ETV monotherapy has been used to prevent hepatitis B reactivation and recurrent graft hepatitis with subsequent graft loss for those without evidence of LAM resistance. The standard dose of 0.5 mg daily was used, although 9 patients initially were treated with a 1-mg dose, which was later changed to 0.5 mg daily. No HBIG was used before, during, or after transplantation; and therapeutic vaccination was not routinely used.

IMMUNOSUPPRESSION

The standard protocol immunosuppression for all patients included induction therapy with basiliximab and tacrolimus with or without mycophenolate mofetil. A tacrolimus concentration target of 8-10 ng/mL was adopted for the initial 3 months, followed by 5-8 ng/mL thereafter. For those who were unable to tolerate tacrolimus or required additional immunosuppression, alternative agents including cyclosporine, sirolimus, everolimus, and corticosteroid were used.

SURVEILLANCE FOR HEPATOCELLULAR CARCINOMA

For patients transplanted for hepatocellular carcinoma (HCC), regular surveillance at intervals of 3-6 months was performed using triphasic contrast computed tomographic or magnetic resonance imaging scanning. No chemotherapy was used in the posttransplant period for those with HCC at the time of transplant.

TRANSIENT ELASTOGRAPHY

Liver stiffness measurement using transient elastography (FibroScan; Echosens, Paris, France) was performed routinely from 2015 onward for all eligible patients. A minimum of 10 valid measurements was obtained for each patient, with the median value representative of the liver stiffness. The results were included in the final analysis only if the success rate was >50% combined with an interquartile range-to-liver stiffness ratio of <30%.

STATISTICAL ANALYSIS

All statistical analyses were performed using SPSS, version 23.0 (IBM Corp). Categorical variables were analyzed using the chi-squared test and Fisher's exact test when appropriate. The Mann-Whitney test was used to analyze continuous independent variables with skewed distribution, and the Wilcoxon signed-rank test was used to analyze pair-related samples. The cumulative incidence rates of events and survival were analyzed using the Kaplan-Meier method, with log-rank testing for comparison. P < 0.05 was considered statistically significant.

HBsAg

The cumulative rate of HBsAg seroclearance was 77% by 3 months, 90% by 1 year, and 95% by 5 years (see Fig. 2). Nine patients (3%) had no serological testing performed as a result of early postoperative mortality or retransplantation. The majority of HBsAg seroclearance occurred early after transplantation, with only 10% occurring after 1 year posttransplant. Of the 242 patients who had HBsAg seroclearance after transplantation, 206 (85%) were sustained without evidence of HBsAg reappearance. The cumulative rate of HBsAg reappearance was 13% at 3 years after initial HBsAg reappearance, with minimal increase after 3 years. The numbers of patients with persistent, transient, and no HBsAg seroclearance and their outcomes are summarized in Fig. 3.

A total of 36 patients had HBsAg reappearance after initial loss of HBsAg. Of these, 22 had fluctuating HBsAg status with episodes of positivity and negativity throughout the follow-up period, and 14 had persistent HBsAg seroreversion. Five out of 36 patients died (4 from HCC recurrence and 1 from aspergillosis). Of the remaining 31 patients, 29 underwent valid transient elastography. There was no significant difference between those patients who had HBsAg reappearance after initial HBsAg loss compared to those who had sustained HBsAg seroclearance (5.1 versus 5.2 kPa, respectively; P = 0.811; Fig. 4).

Fourteen (6%) patients had persistently positive HBsAg without any evidence of seroclearance. None of these patients had any virological rebound. Five patients died of unrelated causes (3 from sepsis/infection, 1 from lymphoma, and 1 from HCC recurrence). Of the remaining 9 patients, 2 had add-on tenofovir early after transplant because of slowly declining HBV DNA and 7 had undetectable HBV DNA with completely normal graft function. There was no significant difference in liver stiffness measurement between those who were persistently positive for HBsAg and those who achieved HBsAg seroclearance and maintained HBsAg negativity (5.5 versus 5.2 kPa respectively; P = 0.523; Fig. 4). Of the 9 patients, all but one had liver stiffness <7.0 kPa, indicating a lack of significant fibrosis. Only 1 had liver stiffness of 20.9 kPa. A liver biopsy performed showed only nonspecific changes without any significant fibrosis, with ultrasonography showing normal graft size and parenchymal echogenicity and with completely normal graft function. The long-term HBsAg negativity rate was durable, with 85% being HBsAg-negative after 1 year posttransplant, extending to 92% at 8 years after transplantation (Fig. 5).

ANTI-HBs ANTIBODY

A total of 108 developed detectable anti-HBs during the follow-up period. This occurred very early within the posttransplant period, with cumulative rates of 31% by 1 month and 40% by 6 months. The rate of anti-HBs development after liver transplant was higher for those receiving grafts from anti-HBs-positive donors compared to those who were anti-HBs-negative (P < 0.001). For those who received grafts from donors who were anti-HBs-positive and anti-HBc-positive, the cumulative rate of anti-HBs development after transplantation at 1 year was 61% compared to 16% for donors who were negative for both (P < 0.001). The majority (83%) who developed detectable anti-HBs had loss of anti-HBs during the follow-up period, with a median time from antibody detection to antibody loss of 4 months (range 0-94). There was no significant difference in the rate of permanent HBsAg loss for those who received a graft from an anti-HBs-positive donor compared to those from an anti-HBs-negative donor (79.9% versus 85.1%, respectively; P = 0.315).

VIRAL LOAD

Of the 265 patients, 253 had available HBV DNA measurements at the time of transplantation. Only 99 (39%) had undetectable HBV DNA at the time of transplant, while 154 (61%) had detectable HBV DNA (Table 2). Of those 154 with detectable HBV DNA, 90 (35%) had HBV DNA ≤4 logs IU/mL, 37 (15%) had HBV DNA >4-6 logs IU/mL, and 27 (11%) had HBV DNA >6 logs IU/mL. The 64 patients with HBV DNA >4 logs IU/mL at the time of transplantation were followed up for a median of 69.5 months compared to 57 months for those with HBV DNA ≤4 logs (P = 0.111). For those with HBV DNA >4 logs IU/mL, 70.3%, 17.2%, and 12.5% had permanent, transient, and no loss of HBsAg, respectively, compared to 83.0%, 13.7%, and 3.3% for those with HBV DNA ≤4 logs IU/mL (P = 0.014). Five patients with HBV DNA >4 logs IU/mL had switch or add-on tenofovir therapy compared to only 1 patient with HBV DNA ≤4 logs IU/mL. There was no significant difference in median liver stiffness for those with HBV DNA >4 logs versus ≤4 logs IU/mL (5.4 versus 5.1 kPa, respectively; P = 0.150) and no difference between the two groups in the proportion of patients with liver stiffness >7.0 kPa (7.0% versus 9.3%, respectively; P = 0.784) and >9.0 kPa (5.3% versus 4.0%, respectively; P = 0.709).

Comparison between those transplanted for severe acute flares and those transplanted for chronic decompensation/HCC showed a significantly shorter median waiting time from listing to transplantation (3 versus 40 days, respectively; P < 0.001) and a significantly higher median HBV DNA at the time of transplant (4.13 versus 0.78 log IU/mL, respectively; P < 0.001).

By year 1 posttransplant, 95% had undetectable HBV DNA, reaching almost 100% by year 2 (Fig. 5). The viral suppression was sustainable in the long term with undetectable HBV DNA observed in 100% at year 8 after liver transplantation (Fig. 5). The rate of HBsAg seroclearance was significantly higher for those with HBV DNA ≤4 logs IU/mL compared to those with higher viral loads (Fig. 6). At 1 year posttransplant, the HBsAg seroclearance rates were 98%, 92%, 81%, and 60% for HBV DNA at transplant of undetectable levels, ≤4 logs IU/mL, >4 to 6 logs IU/mL, and over 6 logs IU/mL, respectively (P < 0.001).

HCC

A total of 97 patients had HCC at the time of transplantation and were followed up for a median of 51 months. After transplant, 88.3%, 10.6%, and 1.1% had persistent, transient, and no HBsAg seroclearance, respectively. Seventy-seven patients had liver stiffness measurement performed, and there was no significant difference in liver stiffness between those with and without HCC (5.3 versus 5.2 kPa, respectively; P = 0.488). There was no significant difference between the proportion of HCC and non-HCC patients with liver stiffness >7.0 kPa (6.6% versus 10.2%, respectively; P = 0.372) and >9.0 kPa (5.3% versus 4.4%, respectively; P = 0.747).

There were a total of 13 HCC recurrences. For those with recurrence, there was a higher rate of HBsAg reappearance compared to those without (45.5% versus 7.4%, respectively; P = 0.003). Of the 36 patients with transient loss of HBsAg and with reappearance, 26 did not have HCC at the time of transplant and there was no occurrence of de novo HCC. The remaining 10 patients had HCC at the time of transplant, of whom 6 had HCC recurrence. Transient elastography was performed in only 1 of the 13 recurrences due to earlier deaths, with normal stiffness of 3.6 kPa.

SURVIVAL

Overall survival rates were 93%, 88%, 86%, and 85% at 1, 3, 5, and 9 years, respectively, after liver transplant (Fig. 7). There were a total of 37 deaths during the follow-up period, of which 20 (54%) were due to sepsis/infection, 9 (24%) to HCC recurrence, 3 (8%) to cardiac arrest, 4 (11%) to malignancy, and 1 (3%) to traumatic cerebrovascular event. Two patients required retransplantations within a few weeks due to hepatic artery thrombosis and nonfunctioning graft.

SAFETY

There were no side effects attributable to ETV reported during the follow-up period. There were no deaths attributed to HBV reactivation or from recurrence of HBV-related graft hepatitis. All 265 patients were on ETV monotherapy as primary prophylaxis after liver transplantation. Six (2%) patients had additional or change in their antiviral prophylaxis during their follow-up period, of whom 3 had additional tenofovir add-on therapy and 3 had switch to tenofovir monotherapy. The reasons for adding or switching to tenofovir and the results after these changes are described in Table 3. Two patients had a history of potential LAM resistance, and tenofovir was used as a precaution despite the HBV DNA being undetectable, with HBsAg fluctuating between negative and positive status. The remaining 4 patients had tenofovir as a precaution because of slowly declining HBV DNA after transplantation; the HBV DNA levels were already low at the time of change (≤2.4 log IU/mL). All 6 patients had change in therapy as a precaution, and none of these 6 patients had evidence of virological rebound. The remaining 260 patients were maintained on ETV monotherapy.

There was a significant increase in median serum creatinine from the time of transplant to 1 year posttransplant (79.0 versus 97.0 μmol/L, respectively; P < 0.001). For those with follow-up to 5 years, there was no significant difference in median serum creatinine levels between 1 and 5 years posttransplant (95.5 versus 96.0 μmol/L, respectively; P = 0.953). Two patients with preexisting chronic renal disease required long-term hemodialysis within 1 year posttransplant, with renal deterioration unrelated to the use of nucleoside analogues.