renal cell carcinoma ( rcc ) is the most common malignancy of the kidney and a cancer of increasing incidence . in korea ,
rcc accounted for 1.85% of the total cancer occurrence in 2012 , and the incidence rate was 8.2 per 100,000 people .
the incidence of this cancer is relatively low among genitourinary malignancy , leading to the management of a lower volume of rcc cases in most hospitals .
therefore , it is difficult to make generalizations based on studies of rcc performed by single center due to the lower number of cases and the possibility of selection bias
. therefore , it is necessary to establish a well - qualified multi - institutional database ( db ) system comprising a large cohort to conduct clinical rcc researches due to the lower incidence of this neoplasm . and
this database should include more variable data than the cancer statistics of national cancer center or health insurance review & assessment service .
examples include the renal mass study of croes ( clinical research office of the endourological society ) , corona ( collaborative research on renal neoplasms association ) project [ 5 
 6789 ] , saturn ( surveillance and treatment update renal neoplasms ) projects   and japanese multicenter studies , which have reported high - quality research results .
some multi - institutional retrospective studies on rcc have also been conducted in korea , but there have been no large db systems to collect data on korean rcc . here ,
we report the establishment of the 1st web - based rcc db system in korea ( korean renal cell carcinoma , korcc ) and summarize the basic characteristics of korean patients with rcc who underwent surgical management .
the new web - based db system was established to collect basic demographic and clinicopathological characteristics of a large cohort of patients with rcc in korea .
this project was approved by local ethics committee at seoul national university bundang hospital ( irb number : b1202/145 - 102 ) .
the data included basic demographic ( such as age , gender , height , and weight ) and clinicopathological characteristics ( such as clinical stage , perioperative parameters , pathological stage , fuhrman nuclear grade and survival data ) ( tables 1 , 2 , 3 , 4 , 5 ) .
private information ( such as resident registration number and hospital i d number ) was excluded to protect the patients ' personal information .
data from a total of 6,849 patients were collected from 8 tertiary care hospitals that agreed to participate in organizing korcc study group as of 1 july 2015 .
these hospitals were chonnam national university hwasun hospital ( 308 cases ) , chungbuk national university hospital ( 178 cases ) , korea university anam hospital ( 105 cases ) , kyungpook university medical center ( 890 cases ) , national cancer center ( 618 cases ) , seoul st .
mary 's hospital ( 883 cases ) , seoul national university bundang hospital ( 1,440 cases ) and seoul national university hospital ( 2,427 cases ) .
data were collected for the management of renal masses of all tumor stages ( pt1 - 4 , n0 - 2 , m0 - 1 ) at the department of urology at each hospital from 1990 to present ( time frame varies among hospitals due to differences in their own db collections ) .
we established the 1st web - based db of korcc , a database comprising renal mass management cases from multiple centers in korea ( www.mebica.net ) .
a total of 6,849 patients were collected nationwide from 8 tertiary care hospitals in korea .
we analyzed data of 5,281 patients with surgical management ( mean follow - up [ fu ] , 32 months ) ( tables 1 , 2 , 3 , 4 , 5 ) .
the patients ' mean age was 55.712.7 years , and 71.2% of the patients were male ( fig .
1 ) . hypertension , diabetes mellitus and chronic kidney disease ( defined as grade 3 or more ) were identified in 38.5% , 14.9% , and 19.4% of the patients , respectively .
the most common symptom was incidentally detected renal mass ( 4,048 cases , 76.9% ) , and the 2nd most common was gross hematuria , which accounted for 10.4% .
preoperative characteristics - such as clinical stage , tumor size , laterality , and location - were described in table 2 .
clinical t1a was the most common ( 54.3% ) stage , and the mean tumor size was 4.84.2 cm .
radical nephrectomy accounted for 62.7% of the total cases , and an open approach was used in 50.7% and 52.2% of radical and partial nephrectomies , respectively ( table 3 ) .
warm ischemia was the most common type of ischemia ( 83.0% ) and mean ischemic time was 25.211.3 minutes .
intraoperative and postoperative transfusions were done in 7.2% and 3.6% of the patients , respectively ( table 4 ) .
a total of 2.9% of severe postoperative complications were of clavien - dindo grade 3 .
the most common nuclear grade was fuhrman grade 2 ( 51.8% ) and the most common histological type was clear cell ( 85.2% ) .
the 5-year overall , cancer - specific and recurrence - free survival rates were 88.1% , 92.2% , and 88.0% , respectively ( table 6 ) .
kaplan - meier survival curves according to stage , nuclear grade and histologic type are shown in figs . 1 , 2 .
we report the 1st establishment of a web - based db system to collect clinicopathological characteristics of rcc in korea .
the korcc web - based db system was launched in 2013 , finally leading to the participation of 8 centers nationwide in 2014 .
it is necessary to collect data from a large cohort of rcc patients to provide better analysis of rcc data in korea .
data from approximately 7,000 rcc cases were collected , and this project remains ongoing to collect more cases .
we believe that this db can represent korean rcc due to its large cohort size and nationwide distribution .
therefore , we invited 8 nationwide tertiary care centers to participate in this project , and they all agreed to join .
this led to the creation of a db that represents rcc characteristics of korean patients .
second , because this system is web - based , there is possibility that patients ' data could be leaked due to security problems .
therefore , we chose an experienced company that has built many web - based clinical trial db systems ( mebixon co. , seoul , korea ) . personal information - such as resident registration number and hospital identification number - was not included in our db system .
this led to the establishment of a secure web - based db system of rcc in korea .
for the good quality of this database , we limited the number of hospital as above . in the future ,
if the database works well , we will invite other hospitals to participate in korcc and provide chances to investigate with this database .
there have been many multicenter based studies on rcc , and croes was the 1st group to establish an international electronic data management system . the global renal mass study driven by croes was started in 2008 to provide a prospective international study on the indications , treatment modalities and outcomes of the management of renal masses .
each center participating in this project included all of the patients with the diagnosis of renal mass during a one - year period .
other examples of international multi - center collections were the corona and saturn projects , which were not web - based .
nevertheless , this type of multicenter collection is necessary to obtain better knowledge on rcc through a db with a large cohort .
this rate was much higher than the rate of approximately 50% in a previous report .
recently , the more common applications of imaging modalities for the evaluation of a variety of nonspecific symptoms has led to higher rates of incidental mass detection and an increased proportion of early stage tumors .
more than half of the patients ( 54.3% ) presented with clinical t1a stage tumors and metastatic tumors were identified only in 6.3% of patients .
it is probable that this rate overestimated the real pattern of presentation because patients with advanced stage disease who were managed by hematooncologic department were not included in our db system .
this relatively higher proportion of low clinical stage contributed to excellent overall and cancer - specific survival rates .
we will likely find more incidental tumors with lower stages with the increasing use of imaging studies in the future .
an open approach was used in 50.7% and 52.2% of radical and partial nephrectomies , respectively .
minimally invasive approaches - such as laparoscopic and robotic surgeries - were used for the remaining cases .
interestingly , robotic approach was used in 3.1% and 23.8% of radical and partial nephrectomies , respectively .
it is well known that the application of robotic surgery in partial nephrectomy can provide good surgical quality including a reduced ischemic time , due to its enhanced 3-dimensional vision and excellent degree of freedom .
these factors contributed to nearly a quarter of the patients undergoing partial nephrectomy being managed by a robotic approach .
although it represented a relatively lower ( 3.1% ) proportion , robotic technology was also used in radical nephrectomy .
pure laparoscopic surgery is a challenging procedure , and some surgeons find laparoscopic radical nephrectomy difficult to perform .
robotic radical nephrectomy can bridge the gap between open and pure laparoscopic approaches for some urologists . as the number of people with private insurance has increased and the cost barrier is not an issue for these patients , the application of robotic technology will continuously increase in the future .
another notable f inding was that proportion of clear cell type was higher ( 85.2% ) in our db compared to that in previous reports ( 60%-80% ) . whether this phenomenon is korean - specific is not known .
the proportion of sarcomatoid differentiation has ranged from 2% to 5% in past reports ; our db revealed a proportion of 2.5% , which was equivalent to other reports .
in addition to this error , some patients ' data were lacking , causing incomplete data collections for some individual patients .
second , the length of fu length was rather short ( mean , 32 months ) but this weak point will be solved with long - term fu in the future .
some patients with advanced stage disease could visit the department of internal medicine and they could be managed without surgical intervention .
then , the database will be able to represent the whole cohorts of korean rcc . in conclusion , the 1st web - based db system to collect rcc data was established in korea .
we report the 1st establishment of a web - based db system to collect rcc data in korea .
 purposethe purpose of this article is to report establishment of the 1st web - based database ( db ) system to collect renal cell carcinoma ( rcc ) data in korea.materials and methodsthe new web - based db system was established to collect basic demographic and clinicopahtological characteristics of a large cohort of patients with rcc in korea . 
 data from a total of 6,849 patients were collected from 8 tertiary care hospitals that agreed to participate in organizing the korean renal cell carcinoma ( korcc ) study group as of 1 july 2015 . 
 basic demographic and clinicopathological characteristics were collected . 
 the data of patients who underwent surgical treatments were analyzed to characterize korean rcc.resultswe established the 1st web - based db of korean rcc , a database comprising renal mass management cases from multiple centers in korea . 
 the data of 5,281 patients who underwent surgical management ( mean follow - up , 32 months ) were analyzed . 
 the most common symptom was incidentally detected renal mass ( 76.9% ) . 
 clinical t1a was the most common ( 54.3% ) stage and mean tumor size was 4.84.2 cm . 
 radical nephrectomy accounted for 62.7% of cases and an open approach was used in 50.7% and 52.2% of radical and partial nephrectomies , respectively . 
 the 5-year overall , cancer - specific and recurrence - free survival rates were 88.1% , 92.2% , and 88.0% , respectively.conclusionswe report the 1st establishment of a web - based db system to collect rcc data in korea . this db system will provide a solid basis for the characterization of korean rcc . 