PREDICTORS OF SUSTAINED RESPONSE TO INTERFERON-BASED THERAPY IN CHRONIC HEPATITIS B

Objective: IFN-based therapy induces long-term remission in ~20% of CHB-patients. Identification of predictors of treatment response can facilitate the clinical decision. Methods: 168 CHB-patients treated with IFN-based therapy were studied. Predictors of end-of-treatment response (ETR) and sustained response (SR) one-year post therapy were identified by non-parametric chi-square test and correlation analysis. Results: Low baseline HBV DNA ( 4xULN) were independent predictors of ETR. Low viral load was stronger predictor than high ALT level. If both factors coexist the probability of ETR was 92%. In HBeAg-negative subjects SR correlates significantly with age below 40 years, evidence of early viral response at 3 rd month, fibrosis stage F<3 (METAVIR) and prolongation of treatment duration. HBeAg-seroconversion up to 6-month post-therapy was the strongest predictor of SR in HBeAgpositive patients. Conclusion: More favorable results could be achieved by pretreatment selection according to patients’ age, baseline viral load, ALT and liver fibrosis. Extension of IFN-treatment in responders may enhance the SR rate.


INTRODUCTION
Chronic hepatitis B virus (HBV) infection continues to be a major global health problem with more than 400 million cases worldwide (1).It is a cause of cirrhosis and hepatocellular carcinoma (1).HBeAg-negative chronic hepatitis B (CHB) is a severe and progressive liver disease with poor prognosis.Spontaneous sustained remissions are very rare and patients early develop cirrhosis (2)(3)(4).This type of CHB is predominant in the Mediterranean region, Eastern Europe and Asia and its prevalence is increasing worldwide (5).
Similarly to other South European countries the majority of chronic hepatitis B patients in Bulgaria are HBeAg-negative.There is a trend for increasing of HBeAg-negative CHB during the last 15 years and nowadays about 80% of subjects in our country are HBeAg-negative (6,7).
Currently there are two global treatment strategies for patients with CHB: IFN-based therapy and long-term viral suppression with nucleoside/nucleotide analogs.Fixed treatment duration of IFN is a significant advantage, but longterm remission could be achieved only in approximately 20% of subjects (8).Investigations of predictors of response to IFN-based therapy were focused mainly on patients with HBeAg-positive CHB.Low viral load as well as high ALT level at baseline has been shown to be independently associated with response to IFN and Peg IFN (9 -11).
In HBeAg-negative CHB, IFN is associated with good end-of treatment response (ETR), but high rates of early relapse upon treatment discontinuation and poor sustained response (SR) rates (12)(13)(14)(15).Identification of predictors of treatment response can facilitate the clinical decision.

Studied patients
We studied 168 patients with chronic HBV infection who were treated with conventional IFN a2a (112 pts) or Peg IFN a2a (56 pts) -table 1.All subjects initially were with active viral replication defined as HBV DNA > 10,000 cp/ml (> 2000 IU/ml) and with elevated ALT level.Co-infections with HDV, HCV and HIV were excluded.All patients were treated with IFN-based therapy according to the relevant knowledge of HBV infection and treatment policy at the corresponding period.
1) Fifty-six of them received Peg IFN alfa-2a 2)112 patients were treated with conventional IFN alfa-2a.Studied patients were treated between 1995 and 2010.Over the years the guidelines for the duration of treatment course evaluated.Due to this reasons 45 patients received 6 month treatment course, while 73 patients were treated for 12 months 3) 40 patients were included in clinical trials and after the initial treatment with "standard" duration they continue to receive further "consolidation" therapy by intermittent application of IFN or Peg IFN in lower doses.The total treatment duration in the discussed group of patients was at least 24 months.

Treatment response
Virological response both at the end-of-treatment (ETR) and one year post therapy (sustained response-SR) was defined as HBV DNA level < 10,000 cp/ml (<2000 IU/ ml).Early virological response was defined as HBV DNA < 10,000 cp/ml at end of 3 rd month of therapy.

Statistics
Predictors of both ETR and SR were identified by nonparametric chi-square test and correlation.

RESULTS
ETR was achieved in 98/168 of subjects (58%).The rest 70/168 of patients (42%) were non-responders.Low baseline HBV DNA level (< 50,000,000 cp/ml) and high ALT level (> 4x above the upper limit of normal) were identified as independent predictors of ETR.
Low viral load was stronger predictor than high ALT level, but if both factors coexist the probability of ETR was 92% (fig.1).Twelve months post therapy the relapsers were 59/ 98 (60%) of end of treatment responders.Globally 39/168 of patients (23%) were with SR.
In HBeAg-negative end-of-treatment responders, SR correlates significantly with age < 40 years before therapy, evidence of early viral response at 3 rd treatment month, lack of advanced fibrosis (F < 3 according to METAVIR) and prolonged treatment duration.Among above factors treatment duration was identified as the strongest predictor of SR (Table 2).HBeAg seroconversion up to 6-month post therapy was the strongest predictor of SR in HBeAg -positive patients.

DISCUSSION
The current study describes the first detailed analysis of predictors of response to IFN-based therapy in Bulgarian patients with chronic HBV infection.Our results confirmed previous findings that baseline viral load and ALT level are strong predictors of response to both conventional and pegylated IFN therapy (9 -11, 15).In our study the threshold of baseline HBV DNA < 50,000,000 cp/ml was quite similar to the results of R. Perrillo et al. for favorable treatment response to conventional IFN in patients with HBV DNA < 200 pg/ml (~56,600,000 cp/ml) (9).Furthermore, in the study of F. Bonino et al. the reported baseline ALT level > 5x ULN was also similar to our findings that ALT > 4x ULN is good predictor of treatment response (15).Our results confirmed data of previous trails for better treatment response in young subjects without cirrhosis or advanced liver fibrosis (9,10).
Recently HBV genotype was also identified as a significant predictor of response to pegylated IFN therapy (11,15).We have not analyzed this factor because genotype D is predominant in Bulgaria and near 100% of CHB patients in our country are infected with genotype D. This genotype was found in all patients enrolled in the National, Multicenter study with Peg interferon alfa-2a (16).In addition, predomination of genotype D has been confirmed recently also in patients with acute hepatitis B (17).And finally, genotype D was detected in all 25 pts tested for HBV genotype in the present study.Based on all these data one can speculate that present study demonstrate the predictors of IFN-based therapy in subjects with HBV genotype D.
Predictors of treatment response were analyzed mainly in patients treated for up to 1 year.A significant advantage of our study is a group of 40 patients who received prolonged IFN-based therapy for at least 24months.We identified the prolongation of treatment duration as the strongest predictor of sustained response among HBeAg-negative patients.Our results corresponded to recent findings in HBeAg-negative CHB patients with genotype D (18).P. Lampertico et al. clearly demonstrated that extension of treatment course from 48 to 96 weeks is associated with increased sustained response rate from 10% to 31% at 1-year post therapy.In addition HBsAg clearance increased from 0% to 6 %, respectively (18).Together all these results clearly suggested that extension of treatment duration in HBeAg -patients may consolidate the early virological response and thus to reduce the relapse rate after treatment discontinuation.

CONCLUSION
Higher rate of SVR with IFN based therapy could be achieved by precise pretreatment selection according to patients' age, baseline viral load, ALT levels and absence of advanced liver fibrosis.Extension of treatment course in subjects with early virological response may enhance the long-term sustained response rate.

Figure 1 .
Figure 1.ETR according to baseline HBV DNA and ALT levels.
, as well as type of IFN (conventional IFN or Peg IFN) was not predictor of SR in both HBeAgnegative and HBeAg-positive subjects.