***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: BACKGROUND Rates of oesophageal/gastric cardia cancer in Linxian , a rural county in north central China , are among the world 's highest , but the risk factors are not well understood . METHODS A nested case-control study of oesophageal and stomach cancers was conducted within a cohort of 29,584 adults who participated in a r and omized nutrition intervention trial . Information on participant characteristics collected during interviews before the trial began was compared between individuals who subsequently developed cancers of the oesophagus ( N = 640 ) or stomach ( N = 539 ) , mainly cardia , and individually matched controls ( control/case ratio = 5 ) . Analyses were performed separately for oesophageal and stomach cancers using conditional logistic regression . RESULTS For oesophageal cancer , tobacco smoking was associated with a significantly elevated risk , with a twofold increase among long-term smokers . Alcohol consumption was uncommon and not related to risk . High consumption of eggs or fresh vegetables  was associated with 20 % reductions in risk , and risk significantly declined as pre-trial body mass index ( BMI ) , an indicator of long-term nutritional status , increased . No increases in risk were associated with intake of pickled vegetables or mouldy foods , although consumption levels at the start of the trial were low . Excess risks of 40 - 80 % were found among individuals who had reported a history of cancer , notably of the oesophagus and stomach , in parents or sibs . For stomach cancer , only low BMI was significantly associated with elevated risk . CONCLUSIONS This study indicates that several risk factors for oesophageal and stomach cancers in Linxian , including smoking , nutritional deficiency , and familial cancer occurrence , resemble those in other areas of the world and contribute partly to the remarkably elevated rates in this area of China It is considered that fruit and vegetable ( F&V ) protect against oesophagus and gastric cancer ( GC ) . However , 2 recent meta‐analyses suggest that the strength of association on GC seems to be weaker for vegetables than for fruit and weaker in cohort than in case‐control studies . No evidence exists from cohort studies about adenocarcinoma of oesophagus ( ACO ) . In 521,457 men and women participating in the EPIC cohort in 10 European countries , information of diet and lifestyle was collected at baseline . After an average of 6.5 years of follow‐up , a total of 330 GC and 65 ACO , confirmed and classified by a panel of pathologists , was used for the analysis . We examined the relation between F&V intake and GC and ACO . A calibration study in a sub‐ sample was used to control diet measurement errors . In a sub‐ sample of cases and a r and om sample of controls , antibodies against Helicobacter pylori ( Hp ) were measured and interactions with F&V were examined in a nested case‐control study . We observed no association with total vegetable intake or specific groups of vegetables and GC risk , except for the intestinal type , where a negative association is possible regarding  total vegetable ( calibrated HR 0.66 ; 95 % CI 0.35–1.22 per 100 g increase ) and onion and garlic intake ( calibrated HR 0.70 ; 95 % CI 0.38–1.29 per 10 g increase ) . No evidence of association between fresh fruit intake and GC risk was observed . We found a negative but non significant association between citrus fruit intake and the cardia site ( calibrated HR 0.77 ; 95 % CI 0.47–1.22 per 100 g increase ) while no association was observed with the non‐cardia site . Regarding ACO , we found a non significant negative association for vegetable intake and for citrus intake ( calibrated HRs 0.72 ; 95 % CI 0.32–1.64 and 0.77 ; 95 % CI 0.46–1.28 per 100 and 50 g increase , respectively ) . It seems that Hp infection does not modify the effect of F&V intake . Our study supports a possible protective role  of vegetable intake in the intestinal type of GC and the ACO . Citrus fruit consumption may have a role in the protection against cardia GC and ACO . © 2005 Wiley‐Liss , Controlled clinical trials of the treatment of acute myocardial infa rct ion offer a unique opportunity for the study of the potential influence on outcome of bias in treatment assignment . A group of 145 papers was divided into those in which the r and omization process was blinded ( 57 papers ) , those in which it may have been unblinded ( 45 papers ) , and those in which the controls were selected by a nonr and om process ( 43 papers ) . At least one prognostic variable was maldistributed ( P less than 0.05 ) in 14.0 per cent of the blinded-r and omization studies , in 26.7 per cent of the unblinded-r and omization studies , and in 58.1 per cent of the nonr and omized studies . Differences in case-fatality rates between treatment and control groups ( P less than 0.05 ) were found in 8.8 per cent of the blinded-r and omization studies , 24.4 per cent of the unblinded-r and omization studies , and 58.1 per cent of the nonr and omized studies . These data emphasize the importance of keeping those who recruit patients for clinical trials from suspecting which treatment will be assigned to the patient under consideration The effect of consumption of fruits , vegetables , and antioxidants on the incidence of gastric cancer  is inconclusive . In this prospect i ve cohort study , we report the association of dietary intake of fruits , vegetables , antioxidants , and baseline serum levels of antioxidants with subsequent incidence of gastric cardia cancer ( GCC ) and gastric noncardia cancer ( GNCC ) . Participants of this study were 29,133 male smokers recruited into the α-Tocopherol , β-Carotene Cancer Prevention study between 1985 and 1988 . At baseline , a self-administered food use question naire with 276 food items was used to assess dietary intake . Baseline serum sample s were stored at −70 ° C . During a median follow-up of 12 years , 243 incident gastric adenocarcinomas ( 64 GCC and 179 GNCC ) were diagnosed in this cohort , of whom 220 ( 57 GCC and 163 GNCC ) had complete dietary information . For GCC , high dietary intake of retinol was protective [ hazard ratio ( HR ) , 0.46 ; 95 % confidence interval ( 95 % CI ) , 0.27 - 0.78 ] , but high intake of α-tocopherol ( HR , 2.06 ; 95 % CI , 1.20 - 3.54 ) and γ-tocopherol ( HR , 1.94 ; 95 % CI , 1.13 - 3.34 ) increased risk . For GNCC , higher intakes of fruits ( HR , 0.51 ; 95 % CI , 0.37 - 0.71 ) , vitamin C ( HR , 0.60 ; 95 % CI , 0.41 - 0.86 ) , α-tocopherol ( HR , 0.78 ; 95 % CI , 0.55 - 1.10 ) , γ-tocopherol ( HR , 0.69 ; 95 % CI , 0.49 - 0.96 ) , and lycopene ( HR , 0.67 ; 95 % CI , 0.47 - 0.95 ) were protective . Our results suggest a difference in the effect of some of these exposures on GCC and GNCC . Tocopherols were associated with higher risk of GCC , whereas dietary intake of fruits , vitamin C , tocopherols , and lycopene seemed protective for GNCC Abstract Purpose . The incidence of adenocarcinoma of the esophagus is increasing in most Western industrialized nations especially in white males . The impact of vitamins on the development of squamous cell carcinoma ( SCC ) and adenocarcinoma ( AC ) of the esophagus has not been eluci date d. The goal of this pilot- study was to analyze the influence of daily vitamin consumption on the frequency of esophageal carcinoma in Germany . Methods . Ninety-nine patients ( males ) with esophageal carcinoma ( 52 with SCC and 47 with AC ) were compared to a control group of 50 r and omly selected males from the Cologne area . Using a computer program to record the data , patients and controls were question ed in detail about their dietary habits . The interaction between known risk factors and the influence of vitamins on esophageal tumor risk were analyzed using logistic regression analysis . Results . The univariate analysis showed a significant risk reduction with increased intake  of β-carotene , vitamin C , vitamin E , and folic acid for both AC and for SCC . The results of logistic regression analysis were compatible with the known risk factors for SCC ( alcohol and tobacco ) and for AC ( obesity , tobacco , and alcohol ) and showed a significant risk reduction with an intake of vitamin E greater than 13 mg/day ( RR=0.13 , 95 % CI=0.1–0.5 , P=0.0004 ) and vitamin C greater than 100 mg/day ( RR=0.33 , 95 % CI=0.11–0.92 , P=0.034 ) for patients with SCC and similar results for patients with AC . Conclusion . Our data showed that low intake of vitamin C and E correlates significantly with the development of squamous cell carcinoma as well as adenocarcinoma of the esophagus in males . The relevance of interaction of vitamins with other dietary factors , alcohol , and tobacco are topics of current research OBJECTIVE To assess the method ologic quality of approaches used to allocate participants to comparison groups in r and omized controlled trials from one medical specialty . DESIGN Survey of published , parallel group r and omized controlled trials . DATA SOURCES All 206 reports with allocation described as r and omized from the 1990 and 1991 volumes of four journals of obstetrics and gynecology . MAIN OUTCOME MEASURES Direct and indirect measures of the adequacy of r and omization and baseline comparisons . RESULTS Only 32 % of the reports described an adequate method for generating a sequence of r and om numbers , and only 23 % contained information showing that steps had been taken to conceal assignment until the point of treatment allocation . A mere 9 % described both sequence generation and allocation concealment . In reports of trials that had apparently used unrestricted r and omization , the differences in sample sizes between treatment and control groups were much smaller than would be expected due to chance . In reports of trials in which hypothesis tests had been used to compare baseline characteristics , only 2 % of reported test results were statistically significant , lower than the expected rate of 5 % . CONCLUSIONS Proper r and omization is required to generate unbiased comparison groups in controlled trials , yet the reports in these journals usually provided inadequate or unacceptable information on treatment allocation . Additional analyses suggest that nonr and om manipulation of comparison groups and selective reporting of baseline comparisons may have occurred 
    Output:
    
: Pooled results from observational studies suggest that antioxidant intake may be protective against esophageal adenocarcinoma ; the data do not support a consistent association between antioxidant intake  and the risk of cardia carcinoma .
These findings suggest possible etiological differences between these two adjacent malignancies