This study demonstrated that CD20+ DLBCL patients with resolved HBV infection had a significantly higher risk of HBV reactivation and hepatitis compared with HBsAg-negative/HBcAb-negative patients after rituximab-containing chemotherapy. Baseline HBcAb positivity and elevated baseline serum ALT levels were independent risk factors for hepatitis in HBsAg-negative patients. An elevated baseline AST level was an independent risk factor for hepatitis in patients with resolved hepatitis B. HBV reactivation could be managed with prompt antiviral therapy followed by the continuation of chemotherapy. HBcAb positivity, HBV reactivation, or hepatitis did not negatively affect patient survival.
Several studies have consistently demonstrated that the incidence of HBV infection is higher in patients with B-cell lymphoma than in the general population [19-22]. Chronic HBV infection was considered to be associated with lymphomagenesis , especially for B-cell lymphoma . In this study, 33.3% (55/165) of patients had resolved HBV infection, which was consistent with the 20%–40% incidence reported in endemic areas . The incidence of HBV reactivation was 3.6% (6/165) in HBsAg-negative patients in this study, but was reported as high as 80% (12/15) in HBsAg-positive lymphoma patients receiving rituximab-containing chemotherapy without prophylaxis .
Compared with HBsAg-negative/HBcAb-negative patients, HBsAg-negative/HBcAb-positive patients had a greater likelihood of developing HBV reactivation (10.9% vs. 0%, P = 0.001). However, Hui et al.  found no significant difference between the two groups in a study of non-Hodgkin’s lymphoma and Hodgkin lymphoma patients, of whom only 20.1% (49/244) received R-CHOP therapy. The incidence of HBV reactivation varied from 2.3% to 23.8% of patients with resolved HBV infection [4,10-13]. The reasons for this discrepancy remain to be elucidated. However, treatment intensity, patient characteristics, and geographic HBV differences may be responsible. Among the patients with resolved hepatitis B, no significant risk factors for HBV reactivation were found. Prospective studies with larger sample sizes are required to investigate the risk factors for resolved hepatitis B.
Hepatitis can be caused by a range of factors, including tumor progression, drug-related factors, heart failure, and severe sepsis. In this study, hepatitis was caused by HBV reactivation in 28.5% (6/21) of patients, and HBV reactivation was accompanied by hepatitis in all of the 6 patients, given that HBV reactivation often causes a disease flare that leads to liver dysfunction. However, HBV reactivation can also be transient and clinically silent if the viral load is low ; thus, HBV reactivation can also occur in the absence of hepatitis [27,28].
Resolved hepatitis B involves interaction between the virus and the immune system. A variety of mechanisms may be involved. Low-level HBV virus replication is the main cause of resolved HBV infection. Other causes include HBV gene mutation, HBV integration into the host chromosome, HBV infection of peripheral mononuclear cells, host immune response abnormalities, and interference by other viral infection. Persistent HBV infection can promote liver disease, thereby leading to hepatitis and cirrhosis .
ALT is primarily localized in the liver, with lower enzymatic activities found in skeletal muscle and heart tissues. AST is localized in heart, brain, skeletal muscle, and liver tissues. Damaged hepatocytes release their contents, including ALT and AST, into the extracellular space . Serum ALT or AST levels are generally considered sensitive indicators of liver cell injury. However, in addition to HBV infection, elevated baseline serum ALT levels can be caused by various other factors, including tumor progression, fatty liver, and diabetes . In contrast to our results, Yeo et al.  found that all the patients who developed HBV reactivation had normal baseline serum ALT levels and that the incidence of hepatitis was similar in HBsAg-negative/HBcAb-negative patients and in patients with resolved HBV infection. However, 53.7% (43/80) of patients in that study were treated without rituximab. Further studies are therefore needed to clarify the relationship between elevated baseline serum ALT levels and the hepatitis risk, as well as the possible mechanisms involved.
Among the 55 HBcAb-positive patients in our study, 8 (14.5%) had elevated baseline serum ALT levels. During the chemotherapy and follow-up period, 22 (40%) of the 55 patients had elevated serum ALT levels. Data on the proportion of HBcAb-positive patients with elevated serum ALT levels were limited. In a study by Yeo et al. , the incidence of elevated serum ALT levels in HBcAb-positive patients was 19.6% during chemotherapy. The reasons for these differences remain unclear. However, differences in patient characteristics and treatment intensities may be responsible. Therefore, there is no obvious association between HBcAb-positive patients and ALT levels, and further studies are warranted.
Several studies demonstrated that rituximab obviously improved outcomes in patients with B-cell lymphoma [2,3]. However, rituximab has been reported to increase the HBV reactivation rate in patients with chronic HBV infection or resolved HBV infection. Although HBV infection control is mediated mainly by HBV-specific cytotoxic T lymphocytes, B lymphocytes are still required for antigen presentation. Rituximab is a chimeric murine/human anti-CD20 monoclonal antibody that alters the activity of T lymphocytes and destroys B lymphocytes, resulting in the failure of antigen presentation and the subsequent expansion of HBV infection in hepatocytes [32,33]. HBV-related hepatitis during rituximab-containing chemotherapy can be severe and fatal [34-36].
According to previous data and our experience, HBV-related hepatitis often develops after 5 or 6 cycles of chemotherapy at an interval of 1 to 13 months after chemotherapy. Antiviral drugs successfully controlled HBV reactivation in most patients, although 2 elderly patients (ages 77 and 84 years) developed fatal HBV-related disease [4,13,37]. In this study, it was reasonable for such patients to undergo close monitoring of HBV serology, HBV DNA, and liver function before each chemotherapy cycle and at least every 3 months during the follow-up period; this is consistent with the monitoring frequency of 1–3 months recommended by the latest European Association for the Study of the Liver (EASL) Clinical Practice Guidelines  and the consensus on the management of lymphoma with HBV infection in China . In addition, in this study, HBsAg and HBV DNA testing was performed in the event of abnormal liver function or suspected hepatitis. Lamivudine successfully controlled HBV reactivation in all 6 affected patients. Prophylactic agents thus may not be recommended for HBsAg-negative/HBcAb-positive patients if close monitoring of HBV DNA is guaranteed.
However, regular monitoring may not be suitable for all patients. Some experts recommend prophylaxis with antiviral drugs in all HBsAg-negative/HBcAb-positive patients who receive rituximab-containing regimens for hematologic malignancies with a high risk of HBV reactivation and/or if close monitoring of HBV DNA is not guaranteed . Lamivudine is widely used for prophylaxis; however, its efficacy is hampered by the development of viral mutations that result in drug resistance . The prophylactic entecavir was found to be effective and associated with minimal resistance in lymphoma patients with resolved hepatitis B , but its long-term use is expensive. More large-scale studies or meta-analyses are required to identify host and viral factors that can help to predict the occurrence of HBV-related hepatitis and thus allow the design of individualized strategies for preventing HBV-related hepatitis. Different approaches based on cost-effectiveness, particularly in HBV-endemic areas, could be used for patients with different risk levels, and antiviral prophylaxis should be continued indefinitely.
In HBsAg-positive patients with non-Hodgkin’s lymphoma, the HBV reactivation-associated mortality was 30%–50% without antiviral prophylaxis . The HBV-related morbidity and overall mortality remained high in lymphoma patients treated with antiviral prophylaxis . In this study, OS was similar in HBsAg-negative/HBcAb-positive patients and HBsAg-negative/HBcAb-negative patients after rituximab-containing chemotherapy. Moreover, no significant difference was observed in OS between patients with and without HBV reactivation or between patients with and without hepatitis. Fukushima et al.  found similar survival rates in HBcAb-positive or HBcAb-negative patients, although their study included other types of lymphoma in addition to DLBCL, and 26.4% (19/72) of patients had not received rituximab-containing therapy. In addition, DLBCL is a heterogeneous disorder with varied clinical outcomes. Hsu et al.  also demonstrated that resolved HBV infection with HBV reactivation was associated with low OS and progression-free survival rates, although the differences were not significant. Further studies are needed to determine the impact of HBV reactivation on the clinical outcomes of lymphoma patients.
Our study had several key points. First, all patients had newly diagnosed DLBCL and received rituximab-containing therapy. Second, we compared the incidence of HBV reactivation or hepatitis between HBcAb-positive and HBcAb-negative patients and identified risk factors for the occurrence of HBV reactivation and hepatitis in HBsAg-negative patients and patients with resolved hepatitis B. Third, we analyzed the effects of HBcAb positivity, HBV reactivation, and hepatitis on survival, which are currently unknown. Furthermore, South China is a highly endemic HBV area, and this is the first to confirm these findings in the southern Chinese population in the largest cancer center in South China.
However, this study was limited by its retrospective nature. First, the assignment of rituximab-containing chemotherapy was not randomized in HBcAb-positive or HBcAb-negative patients but was instead based on the consideration of individual patients, leading to inevitable bias in terms of which patients received rituximab. Second, this study was limited to the analysis of patients from a single institute. All of the patients were Chinese, and our findings therefore must be confirmed in patients from other parts of Asia and in other ethnic groups.