You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
conventional radiation therapy ( rt ) is a widely recognized treatment for hepatocellular carcinoma ( hcc ) .
however , conventional rt currently plays only a limited role in hcc treatment due to its low efficacy and the low tolerance of the liver for its effects .
the total dose of irradiation has been shown to be the most significant factor associated with response .
cell survival with lengthy treatment time was increased , presumably as a consequence of cellular repair mechanisms . to improve local tumor control and overall survival , dose escalation during short treatments has become an important issue .
it is not possible with conventional rt to deliver a high radiation dose to a treatment volume in a short time without also irradiating some normal hepatic tissue with a high dose .
stereotactic body radiation therapy ( sbrt ) is the only modality that can deliver a high dose in a short time to well - defined hepatic tumors with a rapid dose fall - off gradient .
sbrt was initially used only for benign and malignant intracranial lesions with the advent of advanced imaging techniques and robotic image - guided radiation technologies . recently ,
local , not whole liver , rt has been attempted by several investigators , and this work has demonstrated that high doses of radiation can be safely delivered to a portion of the liver .
these results suggest a benefit of the combination of radiation and chemotherapy for advanced hcc with portal vein tumor thrombosis ( pvtt ) . here
we report the use of cyberknife with transarterial chemolipiodolization ( tacl ) treatment for advanced hcc developing extrahepatic biliary obstruction ( ehbo ) , which showed a partial response and safety .
a 63-year - old man was admitted to our hospital complaining of epigastric discomfort and jaundice .
he was diagnosed as a hepatitis b virus ( hbv ) carrier , a status he had held for 20 years without receiving treatment .
he had complained of epigastric discomfort with abdominal bloating and jaundice with pruritus a few months previously associated with a 25-kg body weight loss over the previous three months .
his initial blood pressure was 120/80 mmhg , pulse rate 78/min , respiratory rate 20/min , and body temperature was 36.4. the physical examination showed icteric sclerae and no palpable mass , abdominal distention , and shifting dullness .
laboratory findings showed white blood cell 4,190/l , hemoglobin 10.2 g / dl , hematocrit 28.3% , platelet 145,000/l , prothrombin time ( pt ) 115% of normal pt , inr 0.93 , aptt ( control / test ) 29.5/31.8 sec , fasting blood glucose 96 mg / dl , urea nitrogen 20.4 mg / dl , creatinine 1.41 mg / dl , total protein 6.59 g / dl , albumin 3.02 g / dl , aspartate aminotransferase ( ast ) 57 u / l , alanine aminotransferase ( alt ) 39 u / l , alkaline phosphatase 687 iu / l , gamma - glutamyl transpeptidase ( ggtp ) 39 u / l , total bilirubin 56.66 mg / dl , direct bilirubin 34.84 mg / dl , alpha - fetoprotein ( afp ) 613 ng / dl , and pivka ii > 2,000 mau / ml .
the serum hepatitis b surface antigen was positive , and hepatitis c antibody was negative .
hepatitis b e antigen was negative , e antibody was positive , and hbv dna titer was 2.0  10 copies / ml . the abdominal ct scan revealed a 5.6  5-cm - sized arterial enhancing , delayed - washout mass with a central necrotic portion in the caudate lobe of liver ( s1 ) , left intrahepatic bile duct dilatation , right portal vein invasion , and underlying liver cirrhosis with splenomegaly and ascites .
, percutaneous transhepatic cholangiographic drainage was performed to lower the elevated bilirubin and to diminish the pruritus .
the fistulography revealed hilar and proximal common hepatic duct obstruction with left intrahepatic duct dilatation ( fig .
the level of total bilirubin was decreased from 57.66 mg / dl to 38.51 mg / dl after the procedure of external bile drainage .
however , the bilirubin level was not decreased any more even though maintaining the draining catheter .
four gold markers were inserted around the region of the target under sono guidance to act as radiographic landmarks .
the total doses administered were 37 gy with a prescription isodose at 80% in three fractions over three consecutive days . at 3 months after cyberknife treatment ,
the size of the mass had decreased from 5.6  5 cm to 4.8  3.2 cm as determined by ct scan ( fig .
3 ) , and total bilirubin and afp levels had decreased from 33.60 to 9 mg / dl and 613 to 300 ng / dl , respectively .
after 4 months , tacl was performed three times per month to reduce the hcc mass , and angiography showed an infiltrating hcc at the caudate lobe without definite hypervascular staining . following consecutive post - cyberknife tacl treatments , symptoms ( jaundice , pruritus , and abdominal discomfort )
finally , total bilirubin and afp levels decreased dramatically from 33.60 to 1.83 mg / dl and from 613 to 0.64 ng / dl , respectively ( fig .
4 ) . in addition , angiography showed no tumor staining at the caudate lobe in the 3rd tacl ( fig .
hcc is the fifth most common cancer and the third most frequent cause of death from cancer worldwide .
however , in korea , it is the third most frequent cause of death and is more prevalent among men in their fourth to fifth decades of life .
jaundice occurs in 19 to 40% of patients with hcc at the time of diagnosis and usually occurs in the later stages of the disease .
hcc may involve the biliary tract in several different ways : tumor thrombi , hemobilia , tumor compression , and diffuse tumor infiltration .
rarely , jaundice may be occurred due to external compression of the major bile ducts by direct tumor encasement or by metastatic lymphadenopathy at the porta hepatis .
the clinical features of this type of hcc include high serum afp level , a history of cholangitis with dilation of the intrahepatic bile duct , aggravating jaundice , and rapidly development of liver dysfunction .
the total serum bilirubin level can increase rapidly and is correlated with alkaline phosphatase and gamma - gtp levels .
based on the underlying pathophysiology , the development of jaundice in hcc can be classified into two types : hepatocellular and cholestatic .
hepatocellular hcc is attributed to an underlying liver cirrhosis and extensive hepatic parenchymal infiltration by the tumor , which leads to hepatic parenchymal insufficiency . over 90% of hcc cases with
some cases may have a reversible cause , such as reactivation of an underlying viral hepatitis or other toxic hepatitis , and should be excluded . in cholestatic hcc , jaundice is caused by obstruction of the bile ducts by the tumor .
mallory et al .   described the first case of hcc invading the gall bladder and obstructing the extrahepatic bile ducts .
this has significant therapeutic and prognostic value because those patients with ehbo secondary to hcc have a higher curative resection rate , which results in a significantly improved survival rate compared with those with intrahepatic biliary obstruction .
evidence from previous studies suggested that the management and prognosis of patients with hcc associated with jaundice depends on the underlying cause of the jaundice .
the first is to stabilize the jaundice by insertion of a draining catheter into the obstructed biliary tree , and the second is to assess the resectability of the tumor using appropriate investigations .
depending on the degree of biliary obstruction and the general condition of the patient , these two aspects of management can be carried out in one or two phases . for patients with unresectable cholestatic - type hcc
whose liver function improves after biliary drainage , other palliative treatments , such as transcatheter arterial chemoembolization , internal radiotherapy , or systemic chemotherapy , should be considered . currently , radiation therapy is the most common treatment for hcc , and it has been reported to have beneficial effects , not only on the main tumor but also on pvtt associated with hcc
. however , its role is currently limited because of the very low radiation tolerance of normal hepatic tissue .
the combination of three - dimensional conformal radiation therapy with tacl for hcc in cirrhotic patients was introduced as an alternative local modality , and the response rate was reported to be about 50% in hcc with pvtt .
some authors have reported that the liver - tolerable dose depends on the volume of liver irradiated , and a small volume of liver tissue can tolerate a higher dose of radiotherapy .
it is not possible with conventional radiation therapy to deliver a high radiation dose to a treatment volume without exposing some normal hepatic tissue to high - dose irradiation .
however , sbrt with the cyberknife can deliver a high dose to well - defined hepatic tumors with an associated rapid dose fall - off outside the tumor volume and preservation of normal hepatic tissue .
were the first to report use of stereotactic radiation in the treatment of liver malignancies .
they suggested a fractionated radiation schedule and reported ( after exclusion of the first five patients ) only one failure out of 41 liver malignancies .
reported that 54 ( 98% ) of 55 tumors were locally controlled after six weeks ( the initial follow - up ) based on computer tomographic findings after a stereotactic single - dose radiation treatment of 60 liver tumors in 37 subjects .
.   demonstrated that sbrt for small hcc less than 32 cc in tumor volume that are ineligible for local treatments showed 25 ( 59.6% ) of 42 patients with complete response and 11 ( 26.2% ) patients with partial response for in - field lesion .
furthermore , in cases of advanced or huge hcc developing obstructive jaundice , combined local sbrt with tacl therapy may prevent the tumor from spreading and lead to relief of obstructive jaundice .
the prognosis of patients with cholestatic - type hcc is generally dismal , but is usually better than that of hcc patients who have jaundice caused by hepatic insufficiency .
the prognosis of this type is closely related to the stage of disease and the location and extent of tumor thrombi in the bile duct . in a study of 49 hcc patients with obstructive jaundice , lau et al .  
reported that nine patients received curative resection , 35 had biliary stents , and five required only supportive treatment .
the overall survival rate of these patients was similar to that of hcc patients without jaundice .
they concluded that good palliation and occasional cure were possible with proper treatment . in conclusion , even though the available clinical data are insufficient to explain the outcome of this case , we believe that sbrt with tacl may represent an appropriate treatment modality for advanced hcc with obstructive jaundice due to its precision and relative safety .
conventional radiation therapy ( rt ) is a widely recognized treatment for hepatocellular carcinoma ( hcc ) . 
 however , conventional rt plays only a limited role in hcc treatment because of its low efficacy and the low tolerance of the liver for this modality . 
 stereotactic body radiation therapy ( sbrt ) was recently developed and represents the most advanced radiation therapy technique currently available . 
 it can deliver a high dose in a short time to well - defined hepatic tumors , with rapid dose fall - off gradients . 
 we believe that sbrt with transarterial chemolipiodolization ( tacl ) may prove promising as a combined treatment modality for hcc due to its precision and relative safety . here 
 we present a case of successful treatment of advanced hcc with obstructive jaundice using this combined modality .