***TASK*** the task is to summarize an input biomedical literature in six sentences 
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    Input: Summary To prospect ively evaluate the prevalence of hepatitis B virus ( HBV ) positivity and study the evolution of HBV profile during  cancer chemotherapy  , serum HBV markers and liver biochemistry were determined in 1008 of 1402 ( 72 % ) cancer patients admitted in our Unit and in all 920 ( 91 % ) who received chemotherapy .  We found that 54 ( 5.3 % ) were HBsAg carriers while 443 ( 44 % ) had at least one HBV marker positive . Of the latter , 405 ( 91 % ) were HBcAb+ve , 321 ( 72 % ) HBsAb+ve and 212 ( 48 % ) HBeAb+ve . No patient was HBeAg+ve . Among 920 chemotherapy receivers , 374 ( 41 % ) were HBcAb+ve , 280 ( 30 % ) HBsAb+ve and 178 ( 19 % ) HBeAb+ve . Fifty ( 5.4 % ) were HBsAg carriers ( versus 0.6 % in Greek blood donors ) . All 50 were systematic ally screened for HBsAg and HBsAb status throughout chemotherapy , during follow-up or until their death , and liver biochemistry was performed before each chemotherapy course . Stable antigenaemia was observed in 43/50 ( 86 % ) while 7/50 ( 14 % ) developed clinical and /or biochemical hepatitis . Six of these seven developed serum anti-HBs antibodies with an associated decrease of serum HBsAg titres . We conclude that reactivation of HBV infection during chemotherapy is not rare ( 14 % ) , while disappearance of HBs antigenaemia is neither a frequent nor usually a permanent phenomenon Hepatitis B virus ( HBV ) reactivation is a well-described complication in cancer patients who receive cytotoxic chemotherapy  and may result in varying degrees of liver damage . As chemotherapy is used increasingly in cancer patients , HBV reactivation during cytotoxic treatment may become a more common problem . In lymphoma patients , the incidence of chronic HBV infection has been reported to be 26 % , of whom 47 % developed HBV reactivation during chemotherapy . However , corresponding data for patients with other malignancies undergoing cytotoxic chemotherapy are not known . In this prospect i ve study , hepatitis B surface antigen ( HBsAg ) was determined in 626 consecutive cancer patients who received cytotoxic chemotherapy over a 12-month period . Seventy-eight patients ( 12 % ) were found to be HBsAg positive . Thirty-four ( 44 % ) developed raised alanine transaminase during their course of chemotherapy . In these 34 patients , hepatitis was attributed to HBV reactivation in 15 patients ( 44 % ) , chronic active HBV infection in 1 patient ( 3 % ) , hepatitis C infection in 1 patient ( 3 % ) , malignant hepatic infiltration in 2 patients ( 6 % ) , and the use of hepatotoxic chemotherapeutic agents in 11 patients ( 32 % ) . The causes of hepatitis were unknown in 4 patients ( 12 % ) . HBV reactivation was more likely to develop in patients who were male , younger age , HBeAg seropositive , and those with lymphoma . Presence of malignant hepatic infiltration , baseline pre-treatment alanine transaminase , total bilirubin , and HBV DNA levels did not correlate with the development of HBV reactivation . Of the 15 patients who developed HBV reactivation , antiviral therapy with lamivudine was available and used in 9 . There was no HBV-related mortality during chemotherapy . It is concluded that in patients with chronic HBV infection under chemotherapy  , HBV reactivation occurs in nearly 20 % of them and accounts for 44 % of hepatitis cases . The risk factors identified include male sex , younger age , HBeAg seropositive , and the diagnosis of lymphoma . In HBV endemic areas , patients with risk factors for HBV reactivation should be identified prior to receiving cytotoxic treatment and monitored closely . The potential benefit of lamivudine requires further confirmation Flaws in the design , conduct , analysis , and reporting of r and omised trials can cause the effect of an intervention to be underestimated or overestimated . The Cochrane Collaboration ’s tool for assessing risk of bias aims to make the process clearer and more Abstract Background This proof-of-concept study compared lamivudine ( LAM ) with a newer antiviral agent , adefovir dipivoxil ( ADF ) , in preventing hepatitis B virus ( HBV ) reactivation in chronic HBV patients undergoing chemotherapy . Methods Hepatitis B surface antigen ( HBsAg ) positive patients intended to undergo chemotherapy  were r and omized to receive either LAM 100 mg daily or ADF 10 mg daily . Anti-viral therapy was started 1 week prior to chemotherapy and until 6 months after completing chemotherapy . The primary outcome was HBV reactivation rate . All patients with viral breakthrough were screened for resistance mutations by direct sequencing . Results Seventy treatment-naïve patients were consecutively r and omized 1:1 to LAM or ADF . The median baseline HBV DNA levels were similar ( LAM 3.36 vs. ADF 3.17 log10 copies/mL , p = 0.860 ) . The median duration was 8.3 months on LAM and 10.6 months on ADF ( p = 0.220 ) . HBV reactivation was observed in 13/35 ( 37.1 % ) on LAM compared with 10/35 ( 28.6 % ) on ADF ( p = 0.611 ) . The median time to HBV reactivation was 4.6 and 8.1 months , on LAM and ADF respectively . Among these 13 patients , 8/13 ( 61.5 % ) on LAM had developed drug resistance mutations but none on ADF had developed drug resistance mutations to ADF ( p = 0.003 ) . Both drugs were well tolerated and no severe drug-related toxicities were reported . Conclusion In this r and omized clinical study , adefovir and lamivudine demonstrated similar efficacy in preventing hepatitis B reactivation in HBsAg-positive patients undergoing chemotherapy . In patients whose hepatitis B reactivated , adefovir was associated with a lower resistance profile Over the past four decades , chemotherapy has played an important role in prolonging survival in breast cancer patients . However , it may also result in undesirable side effects such as hepatitis B virus ( HBV ) reactivation seen in this study . With the increasing use of chemotherapy paralleling the rise in breast cancer incidence , the occurrence of HBV reactivation is likely to further increase . Several strategies use lamivudine to deal with this problem . Initially , lamivudine had been used to treat patients who developed alanine transaminase elevation attributable to HBV reactivation during chemotherapy .  However , using this strategy , fatal reactivation has also been reported . Later studies have suggested that prophylactic lamivudine significantly reduces HBV reactivation and its associated morbidity . However , these studies were based mainly on patients with lymphoma , whereas studies on breast cancer patients were few . Moreover , these studies were retrospective . Recently , a prospect i ve study has recommended that deferred preemptive lamivudine could be a comparable alternative to the prophylactic strategy . However , it was not a r and omized controlled study . In this study , it was examined the efficacy of the prophylactic strategy in hepatitis B s-antigen seropositive breast cancer patients during chemotherapy  using a prospect i ve , r and omized controlled study . Two groups were studied . One group consisted of 21 patients who were treated with prophylactic lamivudine , the other group consisted of 21 patients who were not treated with prophylactic lamivudine .  The results showed that the prophylactic lamivudine strategy significantly decreased the incidence of HBV reactivation ( 0 vs. 28.6 % , P = 0.021 ) . It was conclude that the prophylactic lamivudine strategy significantly reduces the incidence of HBV reactivation for hepatitis B s-antigen seropositive breast cancer undergoing chemotherapy Breast cancer is a rapidly increasing problem in many developing countries , and cytotoxic chemotherapy is now an integral part of its management . In several developing countries , the carriage of hepatitis B virus ( HBV ) in cancer patients may be as high as 12 % , and such patients are at risk of developing fatal HBV reactivation during chemotherapy . HBV reactivation is well recognized in patients with hematological malignancies , but limited data are available on patients with other , more common , cancers , such as breast cancer . Recent data have suggested that increased viral replication , an indication of HBV reactivation , may precede clinical hepatitis . In the absence of serial HBV DNA monitoring , HBV reactivation during chemotherapy may have been underestimated . In this prospect i ve study , breast cancer patients who were hepatitis B surface antigen ( HBsAg ) seropositive were followed up during chemotherapy . The main objectives were to determine the incidence of HBV reactivation in breast cancer patients undergoing conventional chemotherapy ;  to investigate whether " serial HBV DNA monitoring " improves the accuracy of diagnosing HBV reactivation when compared with previous schema that only measured HBV DNA at the time of clinical hepatitis ( " conventional monitoring " ) ; and to assess the clinical consequences as a result of developing the condition . The secondary objective was to identify risk factors associated with this condition . Over an 18-month period , 41 patients were studied . Ten developed HBV reactivation by conventional monitoring criteria , but with serial HBV DNA monitoring , seven additional patients were diagnosed when increased HBV DNA levels were detected before , but not concomitant with , clinical hepatitis . Thus , a total of 17 patients ( 41 % ) developed HBV reactivation . Premature termination of chemotherapy or delay in treatment schedules occurred in 71 % of the patients who developed viral reactivation , as compared with 33 % in those who did not develop the condition ( P = 0.019 ) . No risk factors associated with the development of HBV reactivation could be identified . Serial monitoring of HBV DNA , in addition to liver function , increases the sensitivity of diagnosing of HBV reactivation , and helps explain some cases that would otherwise be labeled as " cryptogenic hepatitis , " for which concomitant HBV DNA measured at the time of hepatitis was undetectable . The present study highlights the importance of monitoring HBsAg-seropositive patients who are receiving chemotherapy for common solid tumors such as breast cancer Purpose : Although the mainstay of treatment of patients with nasopharyngeal carcinoma ( NPC ) had been radiotherapy , chemotherapy has increasingly been adopted in conjunction with radiation and in advanced disease . In parts of Asia where NPC is prevalent , it is also known that around 10 % of the population has chronic hepatitis B virus ( HBV ) infection . Cancer patients who are HBV carriers are frequently complicated by HBV reactivation during chemotherapy . This may result in liver damage , which disrupts anticancer therapy and compromises the patients ' prognosis . In its most severe form , fatal hepatic failure may occur . With the increasing use of chemotherapy in NPC , the occurrence of HBV reactivation is likely to increase further . Although recent reports have suggested that the antiviral agent lamivudine may reduce HBV reactivation and its associated morbidity , there has been no data on this aspect in NPC patients . This study assessed the role of lamivudine in preventing HBV reactivation and its associated morbidity in NPC patients who have chronic HBV infection and are undergoing chemotherapy .  Material s and Methods : Two groups were studied . One group consisted of 16 patients who received prophylactic lamivudine prior to and until 8 weeks after discontinuing chemotherapy .  The other comprised 21 historical control subjects who underwent chemotherapy without prophylactic lamivudine .  The outcomes were compared . Results : With prophylactic lamivudine , there were significantly fewer incidences of hepatitis ( 6.7 % vs 33.3 % , P = 0.047 ) and HBV reactivation ( 0 % vs 28.6 % , P = 0.027 ) , and less disruption of chemotherapy ( 18.8 % vs 67.7 % , P = 0.045 ) . Conclusion : Prophylactic lamivudine significantly reduces the incidence and morbidity of HBV reactivation in NPC patients undergoing chemotherapy Hepatitis B reactivation due to chemotherapy is a cause of serious morbidity and mortality in some of the patients with cancer . In this study , we retrospectively assessed the prevalence of hepatitis B reactivation among the patients undergoing cytotoxic chemotherapy .  We investigated efficacy of lamivudine prophylaxis against hepatitis B reactivation as well Purpose Prophylactic lamivudine to prevent chemotherapy-induced hepatitis B virus ( HBV ) reactivation has been widely adopted in hematological cancer patients . We examined the deferred preemptive strategy , upon rising viremia , in breast cancer ( BC ) patients based on sensitive serum HBV DNA level monitoring in a non-r and omized controlled study . Patients and methods Baseline virological profiles before cytotoxic chemotherapy were retrospectively analyzed in historical BC and non- 
    Output:
    
Quality Assessment for Cohort Studies Using the NewcastleOttawa Scale Absolute Risk for HBV Reactivation in Patients With Chronic HBV Across All Solid Tumors The risk for HBV