Risk of hepatitis B virus reactivation in oncological patients treated with tyrosine kinase inhibitors:A case report and literature analysis

Hepatitis B virus(HBV)reactivation(HBVr)represents a severe and potentially life-threatening condition,and preventive measures are available through blood test screening or prophylactic therapy administration.The assessment of HBVr traditionally considers factors such as HBV profile,including hepatitis B surface antigen(HBsAg)and antibody to hepatitis B core antigen,along with type of medication(chemotherapy;immunomodulants).Nevertheless,consideration of possible patient’s underlying tumor and the specific malignancy type(solid or hematologic)plays a crucial role and needs to be assessed for decision-making process.

Overview of the immunological mechanisms in hepatitis B virus reactivation:Implications for disease progression and management strategies

Hepatitis B virus(HBV)reactivation is a clinically significant challenge in disease management.This review explores the immunological mechanisms underlying HBV reactivation,emphasizing disease progression and management.It delves into host immune responses and reactivation’s delicate balance,spanning innate and adaptive immunity.Viral factors’disruption of this balance,as are interac-tions between viral antigens,immune cells,cytokine networks,and immune checkpoint pathways,are examined.Notably,the roles of T cells,natural killer cells,and antigen-presenting cells are discussed,highlighting their influence on disease progression.HBV reactivation’s impact on disease severity,hepatic flares,liver fibrosis progression,and hepatocellular carcinoma is detailed.Management strategies,including anti-viral and immunomodulatory approaches,are critically analyzed.The role of prophylactic anti-viral therapy during immunosuppressive treatments is explored alongside novel immunotherapeutic interventions to restore immune control and prevent reactivation.In conclusion,this compre-hensive review furnishes a holistic view of the immunological mechanisms that propel HBV reactivation.With a dedicated focus on understanding its implic-ations for disease progression and the prospects of efficient management stra-tegies,this article contributes significantly to the knowledge base.The more profound insights into the intricate interactions between viral elements and the immune system will inform evidence-based approaches,ultimately enhancing disease management and elevating patient outcomes.The dynamic landscape of management strategies is critically scrutinized,spanning anti-viral and immunomodulatory approaches.The role of prophylactic anti-viral therapy in preventing reactivation during immunosuppressive treatments and the potential of innovative immunotherapeutic interventions to restore immune control and proactively deter reactivation.

Risk of hepatitis B virus reactivation in cancer patients undergoing treatment with tyrosine kinase-inhibitors

This editorial commented on an article in the World Journal of Gastroenterology titled“Risks of Reactivation of Hepatitis B Virus in Oncological Patients Using Tyrosine Kinase-Inhibitors:Case Report and Literature Analysis”by Colapietro et al.In this editorial,we focused on providing a more comprehensive exploration of hepatitis B virus reactivation(HBVr)associated with the usage of tyrosine kinase inhibitors(TKIs).It includes insights into the mechanisms underlying HBV reactivation,the temporal relationship between TKIs and HBV reactivation,and preventive measures.The aim is to understand the need for nucleos(t)ide analogs(NAT)and serial blood tests for early recognition of reactivation and acute liver injury,along with management strategies.TKIs are considered to be an intermediate(1%-10%)of HBVr.Current guidelines stipulate that patients receiving therapy with high or moderate risks of reactivation or recent cancer diagnosis must have at least tested hepatitis B surface antigen,anti-hepatitis B core antigen(HBc),and anti-hepatitis B surface antibody.Anti-HBc screening in highly endemic areas means people with negative tests should be vaccinated against HBV.Nucleoside or nucleotide analogs(NAs)like entecavir(ETV),tenofovir disoproxil fumarate(TDF),and tenofovir alafenamide(TAF)form the basis of HBV reactivation prophylaxis and treatment during immunosuppression.Conversely,lamivudine,telbivudine,and adefovir are generally discouraged due to their reduced antiviral efficacy and higher risk of fostering drug-resistant viral strains.However,these less effective NAs may still be utilized in cases where ETV,TDF,and TAF are not feasible treatment options.

Investigating the reactivation of historical landslides during the 2022 Luding M_(S)6.8 earthquake

On September 5,2022,a strong earthquake with a magnitude of MS6.8 struck Luding County in Sichuan Province,China,triggering thousands of landslides along the Dadu River in the northwest-southeast(NW-SE)direction.We investigated the reactivation characteristics of historical landslides within the epicentral area of the Luding earthquake to identify the initiation mechanism of earthquake-induced landslides.Records of the two newly triggered and historical landslides were analyzed using manual and threshold methods;the spatial distribution of landslides was assessed in relation to topographical and geological factors using remote sensing images.This study sheds light on the spatial distribution patterns of landslides,especially those that occur above historical landslide areas.Our results revealed a similarity in the spatial distribution trends between historical landslides and new ones induced by earthquakes.These landslides tend to be concentrated within a range of 0.2 km from the river and 2 km from the fault.Notably,both rivers and faults predominantly influenced the reactivation of historical landslides.Remarkably,the reactivated landslides are characterized by their small to medium size and are predominantly situated in historical landslide zones.The number of reactivated landslides surpassed that of previously documented historical landslides within the study area.We provide insights into the critical factors responsible for historical landslides during the 2022 Luding earthquake,thereby enhancing our understanding of the potential implications for future co-seismic hazard assessments and mitigation strategies.

Navigating the complex terrain of hepatitis B virus reactivation in the era of Bruton tyrosine kinase inhibitors

In this editorial,we offer a summary of the risk associated with hepatitis B reactivation(HBVr)in the setting of both solid and hematologic malignancies treated with Bruton tyrosine kinase(BTK)inhibitors,with insights derived from current studies.Furthermore,we emphasize the critical need for a framework regarding robust risk evaluation in patients undergoing such treatments.This framework is essential for identifying those at increased risk of HBVr,enabling healthcare providers to implement proactive measures to prevent reactivation and ensure the safe administration of BTK inhibitor therapy.

Prevention of hepatitis B reactivation in patients with hematologic malignancies treated with novel systemic therapies:Who and Why?

The risk of reactivation in patients with chronic or past/resolved hepatitis B virus(HBV)infection receiving chemotherapy or immunosuppressive drugs is a wellknown possibility.The indication of antiviral prophylaxis with nucleo(t)side analogue is given according to the risk of HBV reactivation of the prescribed therapy.Though the advent of new drugs is occurring in all the field of medicine,in the setting of hematologic malignancies the last few years have been characterized by several drug classes and innovative cellular treatment.As novel therapies,there are few data about the rate of HBV reactivation and the decision of starting or not an antiviral prophylaxis could be challenging.Moreover,patients are often treated with a combination of different drugs,so evaluating the actual role of these new therapies in increasing the risk of HBV reactivation is difficult.First results are now available,but further studies are still needed.Patients with chronic HBV infection[hepatitis B surface antigen(HBsAg)positive]are reasonably all treated.Past/resolved HBV patients(HBsAg negative)are the actual area of uncertainty where it could be difficult choosing between prophylaxis and pre-emptive strategy.

Reactivation of hepatitis B virus infection – an important aspect of multifaceted problem

In this editorial we comment on the article published in the recent issue of the W orld Journal of Gastroenterology.We focus specifically on the problem of occult hepatitis B virus(HBV)infection,that is a result of previous hepatitis B(PHB)and a source for reactivation of HBV.The prevalence of PHB is underestimated due to the lack of population testing programs.However,this condition not only com-plicate anticancer treatment,but may be responsible for the development of other diseases,like cancer or autoimmune disorders.Here we unveil possible mecha-nisms responsible for realization of these processes and suggest practical approa-ches for diagnosis and treatment.

CXCL10 Induces Lytic Reactivation of EBV through EXTL1

Epstein-Barr virus (EBV) infects over 90% of the global population, establishing latent infections in most individuals. Under specific conditions like inflammation and immune suppression, EBV can be reactivated, leading to the initiation and progression of related diseases. While inflammation is known to induce EBV reactivation, the precise mechanisms underlying this phenomenon remain unclear. Chemokine (C-X-C motif) ligand (CXCL10), a key inflammatory factor, plays a significant role in various infectious diseases. In this study, we investigated how CXCL10 levels regulate the transition between the latent and lytic replication phases of the EBV lifecycle using cell culture, Western blot, fluorescent quantitative PCR, immunofluorescence, and flow cytometric apoptosis assays. Our findings indicate that CXCL10 induces EBV transition from latency to lytic replication through its receptor CXCR3 by regulating the downstream effector, exostosis-like glycosyltransferase 1. Additionally, CXCL10 activates the JAK2/STAT3 pathway. This study confirms the role of CXCL10 in promoting EBV lytic replication, providing crucial insights into the pathogenic mechanisms of inflammation-triggered EBV reactivation.

Hepatitis B virus reactivation in patients treated with monoclonal antibodies

Hepatitis B virus(HBV)reactivation poses a significant clinical challenge,espe-cially in patients undergoing immunosuppressive therapies,including mono-clonal antibody treatments.This manuscript briefly explores the complex rela-tionship between monoclonal antibody therapy and HBV reactivation,drawing upon current literature and clinical case studies.It delves into the mechanisms underlying this phenomenon,highlighting the importance of risk assessment,monitoring,and prophylactic measures for patients at risk.The manuscript aims to enhance the understanding of HBV reactivation in the context of monoclonal antibody therapy,ultimately facilitating informed clinical decision-making and improved patient care.This paper will also briefly review the definition of HBV activation,assess the risks of reactivation,especially in patients treated with monoclonal antibodies,and consider management for patients with regard to screening,prophylaxis,and treatment.A better understanding of patients at risk can help clinicians provide optimum management to ensure successful patient outcomes and prevent morbidity.

Hepatitis B and C virus reactivation in immunosuppressed patients with inflammatory bowel disease

In recent years,a number of case reports and clinical studies have highlighted the risk of hepatitis B and C virus reactivation in patients with inflammatory bowel disease who are treated with immunosuppressive drugs.The cases of viral hepatitis reactivation that have been reported are characterized by a wide range of clinical manifestations,from viremia without clinically relevant manifestations to fulminant life-threatening hepatitis.The development and dissemination of biological immunosuppressive drugs have led to a significant increase in the number of reports of interest to physicians in a variety of clinical settings.On this topic,there have been a number of published guidelines and reviews that have collected the available evidence,providing recommendations on prophylactic and therapeutic strategies and methods for monitoring patients at risk.However,it should be noted that,to date,very few clinical studies have been published,and most of the recommendations have been borrowed from otherclinical settings.The published studies are mostly retrospective and are based on very heterogeneous populations,using different therapeutic and prophylactic regimens and obtaining conflicting results.Thus,it seems clear that it is desirable to concentrate our efforts on prospective studies,not conducting further reviews of the literature in the continued absence of new evidence.

Involvement of X-chromosome reactivation in augmenting cancer testis antigens expression:A hy pothesis

Cancer testis antigens(CTAs)are attractive targets for tumor imm unotherapy because of their tumor specific expression,Since more than half of confirmed CTAs are located on the X-chromosome,we asked whether there is a link between CTA expression and X-chromosomes.Recent reports have shown that reactivation of the inactive X-chromosome,known as X-chromosome reactivation(XCR),a unique phenomenon that exists in many high-risk tumors in women,can transform the expression of many X-linked genes from monoallelic to biallelic.

Reactivation of hepatitis B virus infection after cytotoxic chemotherapy or immunosuppressive therapy

Reactivation of hepatitis B is defined as the recurrence or an abrupt rise in hepatitis B virus(HBV) replication,often accompanied by an increase in serum transaminase levels,and both events occurring in a patient with a previous inactive hepatitis B infection.This reactivation can occur in situations in which the ratio of HBV replication and immune response is altered.It can happen during the treatment of hemato-oncological malignancies with chemotherapy and in immunosuppression of autoimmune diseases.Clinical manifestations of hepatitis B reactivation are variable and can range from asymptomatic to acute hepatitis,which are sometimes serious and result in acute liver failure with risk of death,and usually occur in the periods between cycles or at the end of chemotherapy.Immunosuppressive drugs such as corticosteroids or azathioprine can induce HBV reactivation in patients carrying hepatitis B virus surface antigen(HBsAg) or anti-HBc,but much less frequently than chemotherapy treatments.The tumor necrosis factorαinhibitors infliximab,etanercept and adalimumab may cause reactivation of hepatitis B,and the overall frequency with infliximab may be similar(50%-66%) to that caused by chemotherapy.Baseline HBV serology is recommended for all patients receiving chemotherapy and immunosuppressive drugs,and HBsAg positive patients should receive anti-HBV prophylaxis to decrease virus reactivation and death rates.

Hepatitis B reactivation in the setting of chemotherapy and immunosuppression- prevention is better than cure

Due to the inherent relationship between the immune system and the hepatitis B virus(HBV) in exposed and infected individuals, immunomodulation associated with the treatment of solid tumours, haematological malignancies and inflammatory disorders has been linked to HBV reactivation(HBVr). Reactivation of HBV infection in the setting of chemotherapy and immunosuppression may lead to fulminant liver failure and death, but there is a cumulative body of evidence that these are potentially preventable adverse outcomes. As chronic hepatitis B is largely asymptomatic but also endemic worldwide, clinicians caring for patients requiring chemotherapy or immunosuppression need to be vigilant of the potential for HBVr in susceptible individuals. Serological screening and prophylactic and pre-emptive antiviral treatment with a nucleos(t)ide analogue should be considered in appropriate settings. Hepatitis B prevalence is examined in this review article, as are the risks of HBVr in patients receiving chemo- and immunosuppressive therapy. Recommendations regarding screening, monitoring and the role of antiviral prophylaxis are outlined with reference to current international associations' guidelines and the best available evidence to date.

Potent antiviral therapy improves survival in acute on chronic liver failure due to hepatitis B virus reactivation

Acute on chronic liver failure(ACLF)is a disease entity with a high mortality rate.The acute event arises from drugs and toxins,viral infections,bacterial sepsis,interventions(both surgical and non-surgical)and vascular events on top of a known or occult chronic liver disease.ACLF secondary to reactivation of chronic hepatitis B virus is a distinct condition;the high mortality of which can be managed in the wake of new potent antiviral therapy.For example,lamivudine and entecavir use has shown definite short-term survival benefits,even though drug resistance is a concern in the former.The renoprotective effects of telbivudine have been shown in a few studies to be useful in the presence of renal dysfunction.Monotherapy with newer agents such as tenofovir and a combination of nucleos(t)ides is promising for improving survival in this special group of liver disease patients.This review describes the current status of potent antiviral therapy in patient with acute on chronic liver failure due to reactivation of chronic hepatitis B,thereby providing an algorithm in management of such patients.

Prevention and management of hepatitis B virus reactivation in patients with hematological malignancies treated with anticancer therapy

Hepatitis due to hepatitis B virus(HBV) reactivation can be severe and potentially fatal, but is preventable. HBV reactivation is most commonly reported in patients receiving cancer chemotherapy, especially rituximabcontaining therapy for hematological malignancies and those receiving stem cell transplantation. All patients with hematological malignancies receiving anticancer therapy should be screened for active or resolved HBV infection by blood tests for hepatitis B surface antigen(HBs Ag) and antibody to hepatitis B core antigen(antiHBc). Patients found to be positive for HBs Ag should be given prophylactic antiviral therapy to prevent HBV reactivation. For patients with resolved HBV infection, no standard strategy has yet been established to prevent HBV reactivation. There are usually two options. One is pre-emptive therapy guided by serial HBV DNA monitoring, whereby antiviral therapy is given as soon as HBV DNA becomes detectable. However, there is little evidence regarding the optimal interval and period of monitoring. An alternative approach is prophylactic antiviral therapy, especially for patients receiving highrisk therapy such as rituximab, newer generation of anti-CD20 monoclonal antibody, obinutuzumab or hematopoietic stem cell transplantation. This strategy may effectively prevent HBV reactivation and avoid the inconvenience of repeated HBV DNA monitoring. Entecavir or tenofovir are preferred over lamivudine as prophylactic therapy. Although there is no well-defined guideline on the optimal duration of prophylactic therapy, there is growing evidence to recommend continuing prophylactic antiviral therapy for at least 12 mo after cessation of chemotherapy, and even longer for those who receive rituximab or who had high serum HBV DNA levels before the start of immunosuppressive therapy. Many novel agents have recently become available for the treatment of hematological malignancies, and these agents may be associated with HBV reactivation. Although there is currently limited evidence to guide the optimal preventive measures, we recommend antiviral prophylaxis in HBs Ag-positive patients receiving novel treatments, especially the Bruton tyrosine kinase inhibitors and the phosphatidylinositol 3-kinase inhibitors, which are B-cell receptor signaling modulators and reduce proliferation of malignant B-cells. Further studies are needed to clarify the risk of HBV reactivation with these agents and the best prophylactic strategy in the era of targeted therapy for hematological malignancies.

Incidence and characteristics of HBV reactivation in hematological malignant patients in south Egypt

AIM:To investigate characteristics of hepatitis B virus(HBV)implicated in HBV reactivation in patients with hematological malignancies receiving immunosuppressive therapy.METHODS:Serum samples were collected from 53 patients with hematological malignancies negative for hepatitis B surface antigen(HBsAg)before the start of and throughout the chemotherapy course.HBV reactivation was diagnosed when the HBsAg status changed from negative to positive after the initiation of chemotherapy and/or when HBV DNA was detected by realtime detection polymerase chain reaction(RTD-PCR).For detecting the serological markers of HBV infection,HBsAg as well as antibodies to the core antigen(antiHBc)and to the surface antigen were measured in the sera by CEIA.Nucleic acids were extracted from sera,and HBV DNA sequences spanning the S gene were amplified by RTD-PCR.The extracted DNA was further subjected to PCR to amplify the complete genome as well as the specific genomic sequences bearing the enhancerⅡ/core promoter/pre-core/core regions(nt1628-2364).Amplicons were sequenced directly.RESULTS:Thirty-five(66%)of the 53 HBsAg-negative patients were found to be negative serologically for antiHBc,and the remaining 18(34%)patients were positive for anti-HBc.Five of the 53(9.4%)patients with hematologic malignancies experienced HBV reactivation.Genotype D1 was detected in all five patients.Four types of mutant strains were detected in the S gene product of HBV strains and were isolated from 3 patients with HBV reactivation:T/S120,L143,and I126.HBV DNA was detected in the pretreatment HBsAg-negative samples in one of the five patients with HBV reactivation.In this patient,sequences encompassing the HBV full genome obtained from sera before the start of chemotherapy and at the time of de novo HBV hepatitis were detected and it showed 100%homology.Furthermore,in the phylogenetic tree,the sequences were clustered together,thereby indicating that this patient developed reactivation from an occult HBV infection.CONCLUSION:Past infection with HBV is a risk factor for HBV reactivation in Egypt.Mandatory anti-HBc screening prior to chemotherapy in patients with hematological malignancies is recommended.

Post-partum reactivation of chronic hepatitis B virus infection among hepatitis B e-antigen-negative women

AIM: To investigate the frequency and timing of post-partum chronic hepatitis B virus(HBV) reactivation and identify its pre-partum predictors. METHODS: Forty-one hepatitis B e antigen(HBe Ag)-negative chronic HBV infected pregnant women were prospectively evaluated between the 28 th and the 32 nd week of gestation. Subjects were re-evaluated at 3-mo intervals during the first post-partum year and every 6 mo during the following years. HBV DNA was determined using real-time reverse transcription polymerase chain reaction(Cobas Taq Man HBV Test) with a lower detection limit of 8 IU/m L. Post-partum reactivation(PPR) was defined as abnormal alanine aminotransaminase(ALT) levels and HBV DNA above 2000 IU/m L. RESULTS: Fourteen out of 41 women(34.1%) had prepartum HBV DNA levels > 2000 IU/m L, 18(43.9%) had levels < 2000 IU/m L and 9(21.9%) had undetectable levels. Fourteen women were lost to follow-up(failure to return). PPR occurred in 8 of the 27(29.6%) women evaluated, all within the first 6 mo after delivery(5 at month 3; 3 at month 6). Five of the 6(83.3%) women with pre-partum HBV DNA > 10000 IU/m L exhibited PPR compared with 3 of the 21(14.3%) women with HBV DNA < 10000 IU/m L(two with HBV DNA > 2000 and the third with HBV DNA of 1850IU/m L), P = 0.004. An HBV DNA level ≥ 10000 IU/m L independently predicted post-partum HBV infection reactivation(OR = 57.02, P = 0.033). Mean pre-partum ALT levels presented a non-significant increase in PPR cases(47.3 IU/L vs 22.2 IU/L, respectively, P = 0.094).CONCLUSION: In the present study, PPR occurred in approximately 30% of HBe Ag-negative pregnant women; all events were observed during the first semester after delivery. Pre-partum HBV DNA level > 10000 IU/m L predicted PPR.

Hepatitis B reactivation in patients receiving direct-acting antiviral therapy or interferon-based therapy for hepatitis C:A systematic review and meta-analysis

AIM To assess the incidence of hepatitis B virus(HBV) reactivation in patients receiving direct-acting antiviral agent(DAA)-based therapy or interferon(IFN)-based therapy for hepatitis C and the effectiveness of preemptive antiHBV therapy for preventing HBV reactivation.METHODS The Pub Med, MEDLINE and EMBASE databases were searched, and 39 studies that reported HBV reactivation in HBV/hepatitis C virus coinfected patients receiving DAAbased therapy or IFN-based therapy were included. The primary outcome was the rate of HBV reactivation. The secondary outcomes included HBV reactivation-related hepatitis and the effectiveness of preemptive anti-HBV treatment with nucleos(t)ide analogues. The pooled effects were assessed using a random effects model. RESULTS The rate of HBV reactivation was 21.1% in hepatitis Bsurface antigen(HBs Ag)-positive patients receiving DAAbased therapy and 11.9% in those receiving IFN-based therapy. The incidence of hepatitis was lower in HBs Agpositive patients with undetectable HBV DNA compared to patients with detectable HBV DNA receiving DAA therapy(RR = 0.20, 95%CI: 0.06-0.64, P = 0.007). The pooled HBV reactivation rate in patients with previous HBV infection was 0.6% for those receiving DAA-based therapy and 0 for those receiving IFN-based therapy, and none of the patients experienced a hepatitis flare related to HBV reactivation. Preemptive anti-HBV treatment significantly reduced the potential risk of HBV reactivation in HBs Agpositive patients undergoing DAA-based therapy(RR = 0.31, 95%CI: 0.1-0.96, P = 0.042).CONCLUSION The rate of HBV reactivation and hepatitis flare occurrence is higher in HBs Ag-positive patients receiving DAA-based therapy than in those receiving IFN-based therapy, but these events occur less frequently in patients with previous HBV infection. Preemptive anti-HBV treatment is effective in preventing HBV reactivation.

A Case of Hepatitis B Reactivation due to the Hepatitis B Virus Escape Mutant in a Patient undergoing Chemotherapy

A 62-year-old man had chronic hepatitis B virus （HBV） infection and was diagnosed with liver cirrhosis. At the time of diagnosis the patient＇s virologic markers were positive for hepatitis B surface antigen （HBsAg）, antibody to hepatitis B e antigen （anti-HBe） and antibody to hepatitis B core antigen （anti-HBc）, while antibody to hepatitis B surface antigen （anti-HBs） and HBV DNA were negative. Later the patient received chemotherapy for malignancy. However, this was interrupted due to elevated liver enzymes. At the same time HBV DNA became positive. Lamivudine （LMV） therapy was administered immediately. However, the levels of serum aminotransferase and total bilirubin （TB） were still rising. Finally the patient died of fulminant hepatic failure. A sequence revealed HBV genotype C （HBsAg subtype adw） with immune escape mutations, F8L, $34L, F41S, G44V, F93C, V96G, Lll0I, C149Y and F161Y. The high morbidity and mortality of this complication is one of the major obstacles to completing the standard treatment for malignancy in HBV carriers. Therefore, the relative risk of antiviral prophylactic failure should be further assessed and the optimal strategy for antiviral prophylaxis in HBsAg-positive patients with oncologic and hematologic malignancies undergoing chemotherapy should be revised.

Three-dimensional distinct element modeling of fault reactivation and induced seismicity due to hydraulic fracturing injection and backflow

This paper presents a three-dimensional fully hydro-mechanical coupled distinct element study on fault reactivation and induced seismicity due to hydraulic fracturing injection and subsequent backflow process,based on the geological data in Horn River Basin,Northeast British Columbia,Canada.The modeling results indicate that the maximum magnitude of seismic events appears at the fracturing stage.The increment of fluid volume in the fault determines the cumulative moment and maximum fault slippage,both of which are essentially proportional to the fluid volume.After backflow starts,the fluid near the joint intersection keeps flowing into the critically stressed fault,rather than backflows to the wellbore.Although fault slippage is affected by the changes of both pore pressure and ambient rock stress,their contributions are different at fracturing and backflow stages.At fracturing stage,pore pressure change shows a dominant effect on induced fault slippage.While at backflow stage,because the fault plane is under a critical stress state,any minor disturbance would trigger a fault slippage.The energy analysis indicates that aseismic deformation takes up a majority of the total deformation energy during hydraulic fracturing.A common regularity is found in both fracturing-and backflow-induced seismicity that the cumulative moment and maximum fault slippage are nearly proportional to the injected fluid volume.This study shows some novel insights into interpreting fracturing-and backflowinduced seismicity,and provides useful information for controlling and mitigating seismic hazards due to hydraulic fracturing.