Dose-response association between hepatitis B surface antigen levels and liver cancer risk in Chinese men and women

Abstract

We aimed at evaluating the risk of liver cancer in different levels of HBsAg among Chinese men and women. We carried out a nested case-control study including 363 cases and 3,511 controls in two population-based cohorts in Shanghai. Plasma samples collected at enrollment were quantified for HBsAg levels using the Architect QT assay. Conditional logistic regression was performed to estimate the odds ratios (ORs) and 95% confidence intervals (95%CIs) for liver cancer, with adjustment for potential confounders. HBsAg was detected in 6.29% of control subjects overall (7.02% in men and 4.98% in women). HBsAg levels were positively associated with liver cancer risk in a dose-response manner (P_trend<0.001). Such association showed a significant gender disparity. With increasing levels of HBsAg, liver cancer risks rose more steeply in men than in women. In men, the adjusted ORs increased from 7.27 (95%CI: 3.49–15.15) at the lowest detectable level of HBsAg (5–9 IU/ml) to 7.16 (95%CI: 3.21–15.96), 34.30 (95%CI: 16.94–69.44), and 47.33 (95%CI: 23.50–95.34) at the highest level of HBsAg (≥1,000 IU/ml) compared to those negative for HBsAg. The corresponding ORs were much lower for women, from 1.37 (95%CI: 0.25–7.47) to 3.81 (95%CI: 1.09–13.28), 7.36 (95%CI: 2.41–22.46), and 16.86 (95%CI: 7.24–39.27), respectively. HBsAg quantification has potential to distinguish individuals at different risks of liver cancer. Men with the lowest detectable level of HBsAg should still pay attention to their liver cancer risks, but those with a higher level may be given a higher priority in future liver cancer surveillance program.

Introduction

Chronic hepatitis B virus (HBV) infection is a global health problem affecting >350 million people worldwide¹. About 80% of liver cancer cases are estimated to be associated with HBV infection, making it one of the most important risk factors in liver carcinogenesis². The examination of hepatitis B surface antigen (HBsAg) has long been used to identify HBV infection. Recently, sensitive and reliable automated quantitative assays have been developed to quantify serum HBsAg levels. The introduction of HBsAg quantification has attracted much attention for its value in the management of chronic hepatitis B^3–6. A lower HBsAg level was reported to be associated with a higher likelihood of HBsAg loss, and a lower risk of hepatitis activity in patients with HBV genotype B or C infection^{7, 8}.

Recently, serum HBsAg level was used to monitor and predict hepatocellular carcinoma (HCC) occurrence in prospective cohort studies^{9, 10}. These prospective studies were conducted among the HBsAg carriers, that is, subjects seropositive for HBsAg. However, few studies have evaluated the relative risk of liver cancer for individuals at different levels of HBsAg compared with the HBsAg-negative subjects. Of note, it is an interesting but unsolved issue whether those carriers with the lowest detectable serum titer of HBsAg, say 0.05 to 9 IU/ml, have the identical or higher risk of liver cancer compared with the HBsAg-negative subjects. Besides, increasing evidence indicates that HBV-related HCC may involve gender disparity and that it may be a type of hormone-responsive malignant tumor^{11, 12}. One remarkable clinical feature of HBV-related HCC is that its incidence is higher in males compared to females¹³. However, little is known about whether gender acts as an effect modifier of the association between serum HBsAg levels and HCC risk.

To evaluate liver cancer risk in relation to different serum levels of HBsAg in the general healthy population may guide the future community-based surveillance and prediction of liver cancer occurrence. To explore whether this association is modified by gender may shed light on the molecular mechanisms of gender disparity in HBV-associated HCC. Thus, we conducted a nested case-control study within two large population-based cohorts in Shanghai to prospectively assess the association of liver cancer risk with specific HBsAg levels.

Materials and Methods

Study Population

The Shanghai Women’s Health Study (SWHS) and the Shanghai Men’s Health Study (SMHS) are two large population-based prospective cohort studies currently on-going in Shanghai, China. The study was approved by the institutional review boards of all collaborating institutions, and all participants provided written informed consents. Details on the cohorts have been described elsewhere^{14, 15}. Briefly, a total of 74,941 eligible women aged 40–70 years and 61,480 eligible men aged 40–74 years were enrolled in the SWHS and SMHS in 1997–2000 and 2002–2006, respectively. We collected information on demographic characteristics, anthropometric measurements, lifestyle, dietary habits, physical activity, disease history, medication history and family history of cancer in baseline survey. Of the study participants in the SWHS and SMHS, 56,830 (75.8%) and 46,111 (75.0%) provided a blood sample. The samples were kept in a portable insulated box with ice packs (at approximately 0–4°C) and processed within 6 hours of collection for long-term storage at −70°C. At the time of sample procurement, a bio-specimen collection form was completed for each participant, which included the information such as the date and time of sample collection. However, we did not collect information about antiviral therapy at the time point of sample collection.

All cohort members were followed for cancer occurrence through in-person follow-up surveys every two to three years and annual record linkage with databases of the population-based Shanghai Cancer Registry, Shanghai Vital Statistics Registry and Shanghai Resident Registry. For the SWHS, the response rates for the first (2000–2002), second (2002–2004), third (2004–2007) and fourth (2007–2011) in-person follow-up surveys were 99.7%, 98.7%, 94.9% and 92.3%, respectively. For the SMHS, the response rates for the first (2004–2008) and second (2008–2011) follow-up surveys were 97.6% and 93.7%, respectively. All possible cancer diagnoses were verified through home visits and review of medical charts by a panel of clinical and pathological experts. Cancers were coded according to the International Classification of Disease, Ninth Revision (ICD-9). Liver cancer was defined as primary malignant tumor with an ICD-9 code of 155.

To preserve precious prediagnostic plasma samples, we carried out a nested case-control study within the SWHS and SMHS. In order to get sufficient statistical power to detect a significant effect modification, and obtain a relatively accurate prevalence estimate of HBsAg in the SWHS and SMHS, we randomly chose a relatively high number of ten control subjects per case. The controls were free of any cancers and were individually matched to each case by age (≤2 years), sex (male or female), date (≤30 days) and time (morning or afternoon) at sample collection, interval since last meal (≤2 hours) and menopausal status (pre- or post-). The present study included 363 incident HCC cases identified during follow-up of the two cohorts through December 2012. Since a total of 21 cases failed to find 10 controls per case, thus, 3,541 matched controls were selected. After further excluding 30 controls from the analysis because of insufficient plasma samples for HBsAg testing, 363 cases and 3,511 eligible controls were included in the analysis.

Quantification of Hepatitis B Surface Antigen Levels

Plasma samples at enrollment were quantified for HBsAg levels using Architect HBsAg QT (Abbott Diagnostic) according to the manufacturer’s instructions. The sensitivity of the Architect assay ranged from 0.05 to 250 IU/ml. Samples with HBsAg titer higher than 250 IU/ml were diluted to 1:100 to bring the reading to the range of the calibration curve. The laboratory personnel were blinded as to the disease status of study subjects whose plasma samples they analyzed. According to the manufacturer’s instructions, sero-negative of HBsAg was defined as a titer of less than 0.05 IU/ml.

Statistical Analysis

Mean and standard deviation (SD) were calculated for continuous variables and percentages were used for categorical variables. Continuous variables were compared with t test and categorical variables were compared with χ² test.

We evaluated the associations of plasma HBsAg status (positive/negative) with selected risk factors among the control subjects, including age (40 to 49, 50 to 59, 60 to 69 and ≥70 years), sex (male/female), body mass index (BMI, <18.50, 18.50–23.99, 24.00–27.99, ≥28.00 kg/m²), hepatitis B e antigen (HBeAg) status (positive/negative), family history of liver cancer (yes/no), history of hepatitis/chronic liver disease (CLD, yes/no). Multivariable logistic regression model was used to estimate the prevalence odds ratios (ORs) and its corresponding 95% confidence intervals (95%CIs). Other factors such as smoking status and alcohol drinking were found not to be associated with the HBsAg status and therefore were not included in the regression model.

We categorized the HBsAg levels into five groups in present study, from <0.05 (i.e., HBsAg-negative group) to 0.05–9, 10–99, 100–999, and ≥1,000 IU/ml. Conditional logistic regression was performed to calculate the ORs and 95%CIs for specific HBsAg levels associated with liver cancer risk. Covariates were selected and adjusted for as they had potential to confound the association between plasma HBsAg levels and liver cancer risk. Covariates included in the final model were as follows: age at interview (years, continuous), BMI (<18.50, 18.50–23.99, 24.00–27.99, ≥28.00 kg/m²), education level (elementary school or less, middle school, high school and college or above), family income (low [<10,000 Yuan per family per year in the SWHS and<500 Yuan per person per month in the SMHS], low to middle [10,000 to 19,999 Yuan per family per year in the SWHS and 500 to 999 Yuan per person per month in the SMHS], middle to high [20,000 to 29,999 Yuan per family per year in the SWHS and 1,000 to 1,999 Yuan per person per month in the SMHS] and high [≥30,000 Yuan per family per year in the SWHS and ≥2,000 Yuan per person per month in the SMHS]), family history of liver cancer (yes/no), HBeAg status (positive/negative), smoking status (yes/no), history of diabetes mellitus (yes/no), cholelithiasis/cholecystectomy (yes/no) and CLD (yes/no). Further analyses by additionally adjusting for total physical activity, tea consumption, alcohol drinking, vegetable and fruit intakes, and total energy intake did not change the results materially, thus we did not enter them into the final model.

We assessed the effect modification of gender on a multiplicative scale by including interaction term between HBsAg levels and gender in an unconditional logistic regression model. In addition to the aforementioned covariates, original matching factors were also included in the models as covariates. Stratified model was used to assess the association between HBsAg levels and liver cancer risk where evidence for interaction was detected.

Statistical analyses were conducted using SAS 9.3 (SAS Institute, Cary, NC). A two-sided P value of <0.05 was considered statistically significant.

Results

Baseline characteristics of liver cancer cases and matched healthy controls were shown in Table 1. Compared with control subjects, cases had lower family income and education level, and were more likely to have reported a family history of liver cancer and a history of other chronic diseases, including CLD, diabetes and cholelithiasis/cholecystectomy. Male cases were more likely to be cigarette smokers compared with controls. There were no significant differences between cases and controls in BMI, total energy intake, vegetable and fruit intakes, physical activity, alcohol drinking, and tea consumption.

Table 1.

Baseline characteristics of participants in the nested case-control study

	All subjects			Women			Men
Characteristics	Cases (n=363)	Controls (n=3511)	P value*	Cases (n=129)	Controls (n=1246)	P value*	Cases (n=234)	Controls (n=2265)	P value*
Age at interview (years)	59.19 ± 9.44	59.21 ± 9.44	0.967	58.75 ± 8.73	58.67 ± 8.77	0.920	59.43 ± 9.83	59.51 ± 9.78	0.908
Body mass index (kg/m2)	24.08 ± 3.54	24.16 ± 3.20	0.696	24.77 ± 3.77	24.56 ± 3.51	0.520	23.70 ± 3.35	23.94 ± 2.98	0.307
Family income (%)			0.043			0.299			0.097
Low	16.34	14.10		24.81	20.55		11.64	10.55
Low to middle	50.42	45.09		42.64	40.93		54.74	47.37
Middle to high	25.21	29.99		22.48	22.63		26.72	34.04
High	8.03	10.82		10.08	15.89		6.90	8.04
Education level (%)			0.001			0.174			0.007
Elementary school or less	23.14	21.7		44.96	41.17		11.11	10.99
Middle school	33.33	31.87		26.36	27.77		37.18	34.13
High school	31.68	26.17		23.26	19.74		36.32	29.71
College or above	11.85	20.25		5.43	11.32		15.38	25.17
Ever had hepatitis/chronic liver disease (%)	36.91	7.26	<0.001	21.71	3.61	<0.001	45.30	9.27	<0.001
Family history of liver cancer (%)	10.74	2.96	<0.001	9.30	2.33	<0.001	11.54	3.31	<0.001
Ever had diabetes (%)	11.85	8.06	0.013	11.63	6.34	0.024	11.97	9.01	0.138
Ever had cholelithiasis or cholecystectomy (%)	16.53	10.94	0.002	20.93	14.45	0.050	14.10	9.01	0.011
Total energy intake (kcal/day)	1840.90 ± 526.30	1820.30 ± 474.10	0.473	1672.50 ± 515.90	1659.50 ± 384.70	0.782	1933.80 ± 509.70	1908.70 ± 495.00	0.461
Vegetable and fruit intake (g/day)	497.50 ± 267.90	519.30 ± 280.40	0.157	511.20 ± 297.00	543.30 ± 293.20	0.237	489.90 ± 250.70	506.00 ± 272.30	0.386
Total physical activity (MET-h/week)	77.92 ± 45.06	81.28 ± 44.34	0.170	102.3 ± 44.77	107.6 ± 46.24	0.211	64.51 ± 39.31	66.81 ± 35.80	0.391
Ever smoker (%)	47.66	42.30	0.049	3.10	3.85	0.670	72.22	63.44	0.008
Ever alcohol drinker (%)	21.49	23.30	0.436	2.33	2.89	0.714	32.05	34.53	0.448
Ever tea drinker (%)	50.41	49.81	0.828	24.03	25.36	0.741	64.96	63.27	0.609
Post-menopausal status (%)	NA	NA	NA	76.74	76.16	0.883	NA	NA	NA
Positive HBsAg status (%)	58.13	6.29	<0.001	41.09	4.98	<0.001	67.52	7.02	<0.001
Positive HBeAg status (%)	22.04	0.48	<0.001	17.83	0.40	<0.001	24.36	0.53	<0.001

^*Continuous variables were compared to use of t test; categorical variables were compared to use of chi-square test.

NA, not available.

Among the 3,511 controls, 221 subjects (6.29%) were seropositive for HBsAg, with the proportion higher in men (7.02%) than in women (4.98%); 17 subjects (0.48%) were seropositive for HBeAg, also with the proportion higher in men (0.53%) than in women (0.40%). Of note, HBeAg was detected in 5.88% of the HBsAg positive controls overall (6.29% in men and 4.84% in women). A seropositive HBsAg status was positively associated with seropositive HBeAg status (OR=48.35, 95%CI: 15.32–152.57), history of CLD (OR=2.58, 95%CI: 1.73–3.85), and family history of liver cancer (OR=2.15, 95%CI: 1.16–3.96). BMI was not associated with HBsAg status among non-obese individuals. However, obesity (BMI ≥28kg/m²) was inversely related to seropositive HBsAg status (OR=0.51, 95%CI: 0.28–0.94) (Table 2). This inverse association may be explained as that those HBsAg carriers tend to be with a poor physical condition, such as chronic hepatitis B and cirrhosis, which subsequently lead to a lower BMI.

Table 2.

Associations between plasma status of hepatitis B surface antigen and selected risk factors among 3,511 control subjects at baseline

Characteristics	HBsAg (+)/(−)	Adjusted OR (95% CI)*
Age at interview (years)
40–49	105/680	1.00(Reference)
50–59	162/961	1.29 (0.88–1.90)
60–69	117/1325	0.83 (0.56–1.25)
≥70	48/476	0.86 (0.52–1.43)
Gender
Female	115/1260	1.00(Reference)
Male	317/2182	1.22 (0.88–1.70)
Body mass index (kg/m2)
<18.50	18/115	1.05 (0.48–2.33)
18.50–23.99	219/1606	1.00(Reference)
24.00–27.99	163/1322	1.00 (0.74–1.34)
≥28.00	32/399	0.51 (0.28–0.94)
HBeAg status
Negative	339/3438	1.00(Reference)
Positive	93/4	48.35 (15.32–152.57)
Hepatitis/chronic liver diseases
No	295/3190	1.00(Reference)
Yes	137/252	2.58 (1.73–3.85)
Family history of liver cancer
No	386/3345	1.00(Reference)
Yes	46/97	2.15 (1.16–3.96)

^*Variables were adjusted for each other in the logistic regression model.

We detected a significant effect modification by gender on the association of liver cancer risk with different sero-status (P for effect modification=0.003) and levels (P for effect modification=0.014) of HBsAg. Positive HBsAg status was strongly associated with an increased risk of liver cancer, with an adjusted OR of 18.22 (95% CI: 11.77–28.19) for men, which was significantly higher than that for women (OR=7.30, 95% CI: 4.07–13.07). Furthermore, risk of liver cancer was positively related to increasing levels of HBsAg in a dose-response manner (P trend <0.001). Such association showed a significant gender disparity. With increasing levels of HBsAg, liver cancer risks rose more steeply in men than in women. In men, compared to those negative for HBsAg, the adjusted ORs increased from 7.27 (95%CI: 3.49–15.15) at the lowest detectable level of HBsAg (0.05–9 IU/ml) to 7.16 (95%CI: 3.21–15.96), 34.30 (95%CI: 16.94–69.44), and 47.33 (95%CI: 23.50–95.34) at the highest level of HBsAg (≥1,000 IU/ml). The corresponding ORs were much lower for women, from 1.37 (95%CI: 0.25–7.47) to 3.81 (95%CI: 1.09–13.28), 7.36 (95%CI: 2.41–22.46), and 16.86 (95%CI: 7.24–39.27), respectively (Table 3). The positive dose-response associations were not materially altered in the HBeAg-negative subjects.

Table 3.

Associations between plasma levels of hepatitis B surface antigen and liver cancer risk for men and women, respectively

	Men			Women			Effect modification P value‡
	Cases / controls	OR (95% CI)*	OR (95% CI) †	Cases / controls	OR (95% CI)*	OR (95% CI)†
All subjects
HBsAg status							0.003
Negative	76/2106	1.00 (Reference)	1.00 (Reference)	76/1184	1.00 (Reference)	1.00 (Reference)
Positive	158/159	27.95 (19.41–40.23)	18.22 (11.77–28.19)	53/62	13.52 (8.47–21.59)	7.30 (4.07–13.07)
HBsAg levels (IU/mL)							0.014
<0.05	76/2106	1.00 (Reference)	1.00 (Reference)	76/1184	1.00 (Reference)	1.00 (Reference)
0.05–9	16/55	8.18 (4.34–15.43)	7.27 (3.49–15.15)	2/19	1.72 (0.38–7.72)	1.37 (0.25–7.47)
10–99	19/35	14.91 (7.72–28.80)	7.16 (3.21–15.96)	5/11	6.23 (2.04–19.04)	3.81 (1.09–13.28)
100–999	48/33	43.66 (24.50–77.80)	34.30 (16.94–69.44)	8/13	9.46 (3.45–25.92)	7.36 (2.41–22.46)
≥1000	75/36	68.62 (39.06–120.57)	47.33 (23.50–95.34)	38/19	32.48 (16.39–64.33)	16.86 (7.24–39.27)
P for trend §		<0.001	<0.001		<0.001	<0.001
HBeAg-negative subjects
HBsAg status							0.001
Negative	76/2104	1.00 (Reference)	1.00 (Reference)	76/1182	1.00 (Reference)	1.00 (Reference)
Positive	101/149	19.28 (13.02–28.54)	18.60 (11.85–29.18)	30/59	8.18 (4.81–13.90)	7.03 (3.87–12.77)
HBsAg levels (IU/mL)							0.006
<0.05	76/2104	1.00 (Reference)	1.00 (Reference)	76/1182	1.00 (Reference)	1.00 (Reference)
0.05–9	14/53	7.33 (3.75–14.33)	7.70 (3.61–16.44)	2/17	2.05 (0.44–9.44)	2.50 (0.52–12.07)
10–99	12/35	9.60 (4.55–20.25)	5.63 (2.34–13.54)	4/11	4.84 (1.45–16.13)	3.57 (0.98–13.08)
100–999	34/32	30.12 (16.03–56.60)	30.87 (14.76–64.57)	7/13	7.99 (2.80–22.82)	6.69 (2.11–21.22)
≥1000	41/29	51.49 (26.18–101.29)	63.63 (29.14–138.94)	17/18	16.34 (7.39–36.14)	15.05 (6.14–36.91)
P for trend§		<0.001	<0.001		<0.001	<0.001

^*Conditional logistic regression models were used without covariate. Matching variables included age, sex, date and time at sample collection, interval since last meal and menopausal status.

^†Conditional logistic regression models included the following covariates: age at interview (entered as continuous variable), body mass index, HBeAg, family history of liver cancer, education, income, smoking status, and history of hepatitis/chronic liver disease, diabetes and cholelithiasis/cholecystectomy. Matching variables included age, sex, date and time at sample collection, interval since last meal and menopausal status.

^‡P value for effect modification by gender on associations between different status and levels of HBsAg and liver cancer risk.

^§Two-sided P trend values were calculated by assigning an ordinal value to each range of HBsAg and treating it as a continuous variable in the conditional logistic regression models.

Discussion

Using data from two large population-based prospective cohort studies in Shanghai, we demonstrated that the increased levels of plasma HBsAg were strongly associated with higher risk of developing liver cancer in a dose-response manner. We firstly reported that gender may act as an effect modifier on this dose-response association in general Chinese population. As the HBsAg level rose, the risk of liver cancer for men increased more steeply than that for women. Of note, men with the lowest detectable level of HBsAg were still at an increased risk of liver cancer compared to those negative for HBsAg. But such significant association was not detected in women.

The SWHS and SMHS enrolled urban Shanghai residents aged 40–74 years at baseline during 1997–2006. In our random sample of 3,511 controls, we found an overall prevalence of HBsAg positivity of 6.29%, with 7.02% in men and 4.98% in women. Of note, most of the HBsAg positive controls (94.12%) were negative for HBeAg. Previous data from an earlier cohort study with subjects enrolled between 1986 and 1989 in urban Shanghai showed a higher prevalence of 9.64% among men aged from 45 to 64 years¹⁶. The prevalence in present study was also lower than that from the first, second, and third nationwide sero-epidemiological surveys on HBV infection in China, which reported the prevalence of 8.8% in 1979, 9.75% in 1992 and 7.18% in 2006^17–19. In 2002, a nationwide sero-epidemiological survey reported a prevalence of 9.09% among Chinese population older than 3 years²⁰. Recently, a population-based, cross-sectional study reported a lower prevalence of 6% in 2 million men aged 21–49 years in rural China from 2010 to 2012²¹. Taken together, these data suggest that the prevalence of serum HBsAg positivity may have declined over the past three decades in China.

A community-based cohort study in Taiwan (The R.E.V.E.A.L.-HBV cohort) indicated a significantly increased risk of HCC with increasing levels of HBsAg⁹. This study conducted among participants seropositive for HBsAg at study entry. The ERADICATE-B study reported that high levels of HBsAg increased risk of HCC in patients with low HBV load¹⁰. However, it was a hospital-based cohort study and the participants were also seropositive for HBsAg at study entry. Recently, a small hospital-based cohort study conducted among 167 Japanese who were treated with nucleos(t)ide analogues indicated that a high level of HBsAg was associated with hepatocarcinogenesis, despite the negative conversion of HBV DNA as a result of long-term nucleos(t)ide analogues therapy²². However, this finding was based on a small number of study subjects with only 9 HCC cases occurring during the study period, thus the results should be interpreted with caution. Of note, a prospective population-based cohort study in 1,271 Alaska Native persons with chronic HBV infection observed an increase risk of developing HCC after HBsAg clearance, with incidence of HCC increasing from 195.7 per 100,000 person-years to 441.6 per 100,000 person-years of follow-up²³. In addition, previous studies have indicated that a lower HBsAg level is associated with better clinical outcomes, including a higher likelihood of HBsAg loss, lower risk of HBeAg-negative hepatitis, cirrhosis and HCC^{7, 8, 24}. To our knowledge, this is one of few prospective studies reporting a dose-response relationship between HBsAg levels and liver cancer risk.

It is hypothesized that the level of serum HBsAg could reflect the complex interplay between virus and immune system and provide complementary information to viral load as measured using HBV DNA levels⁴. HBsAg levels was shown to be a surrogate marker of infected cells in the liver and reflect the transcriptional activity of cccDNA⁴. It was postulated that chronic HBsAg-induced hepatocellular injury triggers the development of HCC. Previous animal studies reported that HBsAg-transgenic mice spontaneously developed HCC after birth^{25, 26}. Extensive studies indicated that HBsAg played a pivotal role in HCC cells. Some HBsAg-induced miRNAs may regulate the expression of HBV, or they may regulate the apoptosis, migration and invasion of HCC cells. For example, HBsAg may repress the expression of the major histocompatibility complex class I-related molecules A and B via induction of cellular miRNAs, thereby preventing elimination of HCC cells²⁷. Cumulative data suggested that HBV envelope proteins functioned as trans-activators which induced cell proliferation and/or cell death of hepatocytes^{26, 28}. It was demonstrated that HBsAg could stimulate proliferation and functional modification of hepatocytes via lymphoid enhancer-binding factor 1 through the Wnt pathway at the pre-malignant stage^{29, 30}. Taken together, these data suggest that higher expression of HBsAg could promote malignant transformation in hepatocytes via direct or indirect effect on many cellular functions, which was consistent with the epidemiological observation of a higher risk of HCC in patients with increasing levels of HBsAg in present study.

We observed a notable gender disparity on the dose-response association between HBsAg levels and liver cancer risk. Previous epidemiological reports indicated that the incidence of HBV-related HCC was higher in males than females¹³. Increasing evidence suggested that sex hormones such as androgens and estrogens played an important role in the development of HBV-related HCC^{11, 12}. It was supposed that androgen may stimulate the androgen signaling pathway and cooperate to the increased transcription and replication of HBV genes¹¹. In contrast, estrogen may play a protecting role against the development of HBV-related HCC through decreasing HBV RNA transcription and inflammatory cytokines levels¹¹. Additionally, sex hormones can also affect HBV-related hepatocarcinogenesis by inducing epigenetic changes such as the regulation of mRNA levels by microRNAs, DNA methylation, and histone modification in liver tissue^{11, 12}. Our study may shed light on the molecular mechanisms of gender disparity in HBV-associated HCC.

A strength of this study is based on its prospective design. The HBsAg level was determined in plasma collected before the development of liver cancer, minimizing the possibility that the HBsAg level was affected by the malignant transformation of hepatocytes or clinical treatment for liver cancer. The present study has some limitations. Our quantification of HBsAg used a single plasma sample obtained at study entry; thus, the changes in levels of HBsAg over time during follow-up could not be assessed. Second, potential confounders such as intake of aflatoxin B1, serum HBV DNA levels, hepatitis C virus infection and acceptance of antiviral therapy were not considered in present study, which may bias the observed association between HBsAg levels and liver cancer risk.

Conclusions

In summary, there is a strong positive dose-response relationship between levels of HBsAg and risks of liver cancer in these population-based cohorts of residents in urban Shanghai. There is a notable gender disparity on the dose-response of risk for liver cancer. Compared to those sero-negative for HBsAg, men with the lowest detectable level of HBsAg are still at an increased risk of liver cancer. With HBsAg levels increasing, the risks rise more steeply in men, suggesting that men with a higher titer of HBsAg may be given a higher priority on future surveillance program of liver cancer.

What’s new?

Hepatitis B surface antigen (HBsAg) is a hallmark of infection with hepatitis B virus, the chronic presence of which greatly increases a person’s risk of liver cancer. Serum titers of HBsAg vary markedly between individuals, however, and it remains uncertain whether different HBsAg levels are associated with liver cancer risk. In this study of male and female population-based cohorts in Shanghai, China, a positive dose-response relationship was observed between HBsAg levels and liver cancer risk. Risk increased most steeply in men, such that men with high HBsAg titers were most likely to develop liver cancer.

Abbreviations

HBV

hepatitis B virus

HBsAg

hepatitis B surface antigen

HCC

hepatocellular carcinoma

SWHS

the Shanghai Women’s Health Study

SMHS

the Shanghai Men’s Health Study

OR

odds ratio

CI

confidence interval

ICD-9

the International Classification of Disease, Ninth Revision

BMI

body mass index

CLD

chronic liver disease

HBeAg

hepatitis B e antigen

NA

not available