***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: In the last three decades , since Luft suggested a link between hospital volume and patient outcome , little has changed . Despite great efforts to formally quantify the relationship between volume and cancer survival , much uncertainty remains . It is intuitive that increased experience ( of the surgeon , the hospital or the ancillary staff ) translates to better patient care but closer analysis of the literature uncovers widespread inconsistency in study design question ing validity of conclusions . Although central isation of cancer services would seem beneficial , definitive evidence is only available regarding pancreatic and oesophageal disease and that pertaining to rectal cancer is heterogeneous and often flawed . A majority of evidence suggests better outcome for patients with rectal cancer managed in high volume centres . There are , however , many variables in data collection and interpretation rendering comparison between studies challenging . Definitions of the rectum range from distance from the anal verge ( inherent disagreement e range 10e16 cm ) , to relationship to sacral promontory ( subject to interpreter variation ) , and location of peritoneal reflection ( can not be interpreted endoscopically ) . Many authors fail to differentiate between sigmoid colon and rectum 3 and , those that do demonstrate wide variation . One of the largest studies , ( more than 7000 patients ) from the Californian Cancer Registry offered no description of tumour location . It concluded that patients undergoing surgery at high volume hospitals were less likely to have permanent colostomies and had better survival rates . The diagnosis of rectal cancer was , however , question able as it was based only on a discharge letter , often written by the most junior team member with no reference to true anatomical location . Most US studies are published from a few high volume institutions with a select patient cohort and are based on retrospective analysis of large data bases which , themselves are notoriously inaccurate . The European experience was recently explored by Ptok in a prospect i ve trial of almost 7000 patients undergoing resection for rectal cancer . This is arguably the most complete data set available to date and great effort was made to overcome common biases . A clear definition of the rectum was provided , hospital volume was Background  Preoperative radiotherapy reduces recurrence rates after surgery for rectal cancer but other variables may also affect outcome . The Stockholm Rectal Cancer Study Group has conducted two prospect i ve r and omized trials on preoperative radiotherapy in rectal cancer OBJECTIVE To determine whether surgical subspecialty training in colorectal surgery or frequency of rectal cancer resection by the surgeon are independent prognostic factors for local recurrence ( LR ) and survival . SUMMARY BACKGROUND DATA Variation in patient outcome in rectal cancer has been shown among centers and among individual surgeons . However , the prognostic importance of surgeon-related factors is largely unknown . METHODS All patients undergoing potentially curative low anterior resection or abdominoperineal resection for primary adenocarcinoma of the rectum between 1983 and 1990 at the five Edmonton general hospitals were review ed in a historic- prospect i ve study design . Preoperative , intraoperative , pathologic , adjuvant therapy , and outcome variables were obtained . Outcomes of interest included LR and disease-specific survival ( DSS ) . To determine survival rates and to control both confounding and interaction , multivariate analysis was performed using Cox proportional hazards regression . RESULTS The study included 683 patients involving 52 surgeons , with > 5-year follow-up obtained on 663 ( 97 % ) patients . There were five colorectal-trained surgeons who performed 109 ( 16 % ) of the operations . Independent of surgeon training , 323 operations ( 47 % ) were done by surgeons performing < 21 rectal cancer resections over the study period . Multivariate analysis showed that the risk of LR was increased in patients of both noncolorectal trained surgeons ( hazard ratio ( HR ) = 2.5 , p = 0.001 ) and those of surgeons performing < 21 resections ( HR = 1.8 , p < 0.001 ) . Stage ( p < 0.001 ) , use of adjuvant therapy ( p = 0.002 ) , rectal perforation or tumor spill ( p < 0.001 ) , and vascular/neural invasion ( p = 0.002 ) also were significant prognostic factors for LR . Similarly , decreased disease-specific survival was found to be independently associated with noncolorectal-trained surgeons ( HR = 1.5 , p = 0.03 ) and surgeons performing < 21 resections ( HR = 1.4 , p = 0.005 ) . Stage ( p < 0.001 ) , grade ( p = 0.02 ) , age ( p = 0.02 ) , rectal perforation or tumor spill ( p < 0.001 ) , and vascular or neural invasion ( p < 0.001 ) were other significant prognostic factors for DSS . CONCLUSION Outcome is improved with both colorectal surgical subspecialty training and a higher frequency of rectal cancer surgery . Therefore , the surgical treatment of rectal cancer patients should rely exclusively on surgeons with such training or surgeons with more experience CONTEXT Hospitals that treat a relatively high volume of patients for selected surgical oncology procedures report lower surgical in-hospital mortality rates than hospitals with a low volume of the procedures , but the reports do not take into account length of stay or adjust for case mix . OBJECTIVE To determine whether hospital volume was inversely associated with 30-day operative mortality , after adjusting for case mix . DESIGN AND SETTING Retrospective cohort study using the Surveillance , Epidemiology , and End Results (SEER)-Medicare linked data base in which the hypothesis was prospect ively specified . Surgeons determined in advance the surgical oncology procedures for which the experience of treating a larger volume of patients was most likely to lead to the knowledge or technical expertise that might offset surgical fatalities . PATIENTS All 5013 patients in the SEER registry aged 65 years or older at cancer diagnosis who underwent pancreatectomy , esophagectomy , pneumonectomy , liver resection , or pelvic exenteration , using incident cancers of the pancreas , esophagus , lung , colon , and rectum , and various genitourinary cancers diagnosed between 1984 and 1993 . MAIN OUTCOME MEASURE Thirty-day mortality in relation to procedure volume , adjusted for comorbidity , patient age , and cancer stage . RESULTS Higher volume was linked with lower mortality for pancreatectomy ( P=.004 ) , esophagectomy ( P<.001 ) , liver resection ( P=.04 ) , and pelvic exenteration ( P=.04 ) , but not for pneumonectomy ( P=.32 ) . The most striking results were for esophagectomy , for which the operative mortality rose to 17.3 % in low-volume hospitals , compared with 3.4 % in high-volume hospitals , and for pancreatectomy , for which the corresponding rates were 12.9 % vs 5.8 % . Adjustments for case mix and other patient factors did not change the finding that low volume was strongly associated with excess mortality . CONCLUSIONS These data support the hypothesis that when complex surgical oncologic procedures are provided by surgical teams in hospitals with specialty expertise , mortality rates are lower A prospect i ve audit of the management of colorectal cancer was established to investigate factors associated with variation in survival observed within the former Wessex region ( population three million ) PURPOSE : The aim of this study was to analyze the impact of institutions and individual surgeons on long-term prognosis after  curative resection of rectal carcinoma . METHODS : We used univariate and multivariate analysis of data from a German prospect i ve , multicenter , patient-care evaluation study . RESULTS : The locoregional recurrence rates and the observed and cancer-related survival rates showed a considerable interinstitutional and intersurgeon variability . Multivariate analysis confirmed the institution and the individual surgeon as significant independent factors influencing locoregional recurrence and survival . There was a statistically highly significant correlation between the rate of locoregional recurrence and survival rate . CONCLUSIONS : The surgeon 's technique and skill has to focus on prevention of locoregional recurrence to achieve good long-term outcome after curative  resection  for rectal carcinoma . New clinical trials on adjuvant treatment have to include quality assurance for surgery and pathology and documentation of the surgeon ( as local code ) 
    Output:
    
This review gives evidence that higher surgeon volume is associated with better overall survival , lower permanent stoma and APER rates