In recent years, the incidence of lymphoma in China has shown a rising trend. According to the statistical data from the Cancer Prevention and Treatment Research Office of Peking University Cancer Hospital, the incidence of lymphoma in Beijing has increased by 5.17% annually from 1998 to 2010. Therefore, lymphoma is receiving more and more attention in clinical work. The diagnosis and treatment of lymphoma have also made remarkable progress in recent years, especially for B-cell lymphoma. With the introduction of the first monoclonal targeted drug rituximab(R), the cure rate of aggressive lymphoma has been improved substantially, and the quality and duration of survival of patients with inert B-cell lymphoma have been greatly improved, and rituximab combined with CHOP-like regimen has become the standard treatment for almost all B-cell lymphomas. The choice is almost all B-cell lymphoma. However, specific complications associated with targeted therapies and immunochemotherapy are also becoming more prominent, affecting clinicians’ treatment choices. Hepatitis B virus (HBV) reactivation is one of the more prominent issues. It is now widely accepted that the prevalence of hepatitis B virus (HBV) infection in patients with non-Hodgkin’s lymphoma (NHL) is higher than that in the general population, especially in Asian countries. However, according to the statistics of the Lymphoma Department of Peking University Cancer Hospital, the positive rate of hepatitis B surface antigen (HBsAg) and core antibody (HBcAb) in NHL patients is 11.6% and 47.9%, both of which are higher than that of the general population. Combined HBV infection was predominant. Since immunochemotherapy (e.g., rituximab) and/or chemotherapy can induce HBV reactivation, leading to fulminant hepatitis and even liver failure, seriously affecting the treatment process and lives of patients. Therefore, experts from the Union for China LymphomaInvestigators (UCLI), together with some experts from infection and hepatology departments, jointly discussed and formulated the Expert Consensus on Prevention and Treatment of HBV Reactivation in Patients Undergoing Immunochemotherapy for Lymphoma, with the aim of standardizing the diagnosis and treatment of lymphoma in China and improving the overall The aim is to standardize the practice of lymphoma treatment in China and improve the overall level of lymphoma treatment. This article will explain the key points of the consensus. Concern about HBV reactivation Although the data reported by several studies vary widely, it is generally believed that the activation rate of HBV in NHL patients after chemotherapy is 20%-70%, especially in patients using rituximab, the activation rate of HBV may be as high as 70%, and the mortality rate after activation without treatment is 13%. Therefore, the National Comprehensive Cancer Network (NCCN) guidelines for the treatment of non-Hodgkin’s lymphoma specifically include a section on “Prevention and treatment of HBV reactivation due to rituximab”, which recommends that patients who are HBsAg and/or HBcAb positive should be given greater attention to HBV reactivation when receiving rituximab therapy and chemotherapy. It is recommended that patients who are HBsAg and/or HBcAb positive should be given more attention to HBV reactivation when receiving rituximab and chemotherapy, and be given anti-HBV therapy in a timely and preventive manner. However, there is no need to be overly fearful about the treatment of such cases and to arbitrarily change the standard treatment regimen, thereby affecting the quality of patient care. For NHL patients with co-infection with HBV, the presence status of HBV should be fully understood before receiving chemotherapy or immunochemotherapy, and patients with positive HBsAg and/or HBcAb should be given full attention and tested for viral load (HBV-DNA), and those with measurable HBV-DNA should be given prophylactic antiviral therapy. Emphasis on prevention Since HBV reactivation often manifests as fulminant hepatitis and hepatic necrosis, leading to liver failure, the prognosis is extremely poor. Therefore, early prophylactic antiviral therapy is clearly preferable to interventional therapy after HBV reactivation has occurred. When to start prophylactic antiviral therapy? The optimal time to start prophylactic antiviral therapy is not yet clear, but studies have generally favored starting 1 week before immunochemotherapy to effectively inhibit viral replication, reduce the incidence of drug resistance, ensure smooth immunochemotherapy, and minimize the occurrence of delayed HBV reactivation after stopping antiviral therapy. When to start lymphoma treatment? The extent to which viral load can be reduced to begin lymphoma treatment is also a matter of debate. The current consensus is that a reduction in baseline viral load (HBV-DNA) to less than 2000 IU/mL is sufficient to continue antiviral therapy while receiving standard rituximab in combination with a CHOP-like regimen. However, it is often the case that the patient’s disease progresses too rapidly to wait for the viral load to drop below a safe baseline before proceeding with lymphoma treatment. In this case, drugs that are likely to cause HBV reactivation (such as glucocorticoids and rituximab) can be temporarily avoided, and the combination of these drugs can be reconsidered after antiviral therapy and the viral load drops below a safe baseline. What is the course of prophylactic antiviral therapy? The course of prophylactic antiviral therapy is also an issue that has not yet been clarified. The course of antiviral therapy is related to the intensity of immunosuppression, resistance to antiviral drugs, and host-virus factors. Considering that HBV reactivation may occur during immune recovery and reestablishment after the end of immunochemotherapy, combined with the available research data, it is recommended that antiviral therapy should be continued for at least 6 months after the end of all chemotherapy (immunochemotherapy), and the duration of antiviral therapy should be extended appropriately according to the pre-immunochemotherapy HBV-DNA level, HBV infection status, and immunochemotherapy regimen. Do all patients need prophylactic antiviral therapy? It is controversial whether prophylactic antiviral therapy should be given to patients who are HBcAb positive, HBsAg negative, and have undetectable HBV-DNA. Chemotherapy regimens containing drugs at high risk of HBV reactivation, such as glucocorticoids and/or rituximab, should be closely monitored for HBV-DNA viral load if prophylactic antiviral therapy is not considered. Rational drug use Preferred nucleoside (acid) analogs with strong HBV inhibition and low resistance rates, such as entecavir, should be used for prophylactic antiviral therapy, especially in patients with high viral loads prior to immunochemotherapy and an expected long duration of antiviral therapy. If the expected duration of immunochemotherapy (or chemotherapy) is <1 year, or for economic reasons, lamivudine can be used, but it is prone to resistance and requires close monitoring of HBVDNA viral load and timely adjustment of the treatment regimen in case of resistance. Reasons for timely monitoring of HBV reactivation HBV reactivation can occur during immunochemotherapy or after the completion of the entire course of treatment, and can even occur more than 1 year after the end of treatment. The possible reasons for this are: the low immune function of the patient's body during immunochemotherapy, which leads to HBV entering an active replication state and an increase in infected hepatocytes; the reestablishment of the patient's immune function after the completion of immunochemotherapy, where T/B lymphocytes recognize and attack HBV-infected hepatocytes, leading to hepatocyte necrosis and inflammatory reactions. Clinical manifestations of HBV reactivation The clinical manifestations of HBV reactivation vary in severity. The milder cases may only show asymptomatic elevation of serum alanine aminotransferase (ALT), and some patients may resolve on their own; the more severe cases may show signs of liver failure such as jaundice, ascites, coagulation abnormalities and encephalopathy, and the death rate is high if effective treatment is not given in time. Therefore, HBV-DNA load and liver function should be monitored closely and timely in clinical practice. Definition of HBV reactivation At present, the definition of HBV reactivation is not uniform, but the more commonly used definitions are: ① during or after immunochemotherapy or immunosuppressive therapy, the HBV-DNA in serum is changed from non-measurable to measurable, or the HBVDNA viral load is increased by more than one logarithmic value compared with the baseline level; ② liver inflammation damage mainly manifested by elevated ALT, and excluding drug-related liver damage, etc. If the liver function is impaired due to other reasons, HBV reactivation can be diagnosed and interventional antiviral therapy should be given promptly. Emphasis on cooperation With the continuous introduction of various targeted drugs, the problem of HBV reactivation has received more and more attention from oncologists, hematologists, hepatologists and infectologists. However, there are still many controversial and uncertain issues that require a fuller evidence-based medical basis and multidisciplinary cooperation. If difficult problems are encountered during the treatment process, or if HBV reactivation occurs in patients, timely communication and cooperation with hepatologists and infectious disease physicians should be established to improve the overall treatment of lymphoma.