***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 
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    ***EXAMPLES*** 
    Input: PURPOSE Experimental studies and indirect clinical evidence suggest that low molecular weight heparins may have antineoplastic effects . We investigated the influence of a low molecular weight heparin dalteparin on the survival of patients with active cancer and acute venous thromboembolism . PATIENTS AND METHODS Survival data were examined in a posthoc analysis in patients with solid tumors and venous thromboembolism who were r and omly assigned to dalteparin or a coumarin derivative for 6 months in a multicenter , open-label , r and omized , controlled trial . All-cause mortality at 12 months was compared between treatment groups in patients with and without metastatic malignancy . The effect of dalteparin on survival was compared between the two patient subgroups . RESULTS During the 12-month follow-up period , 356 of 602 patients with solid tumors and acute venous thromboembolism  died . Among patients without metastatic disease , the probability of death at 12 months was 20 % in the dalteparin group , as compared with 36 % in the oral anticoagulant group ( hazard ratio , 0.50 ; 95 % CI , 0.27 to 0.95 ; P = .03 ) . In patients with metastatic cancer , no difference in mortality between the treatment groups was observed ( 72 % and 69 % , respectively ; hazard ratio , 1.1 ; 95 % CI , 0.87 to 1.4 ; P = .46 ) . The observed effects of dalteparin on survival were statistically significantly different between patients with and without metastatic disease ( P = .02 ) . CONCLUSION The use of dalteparin relative to coumarin derivatives was associated with improved survival in patients with solid tumors who did not have metastatic disease at the time of an acute venous thromboembolic event . Additional studies are warranted to investigate these findings Clinical occurrence of subclavian venous thrombosis due to indwelling catheters is rare , but there is some evidence that sub clinical thrombosis frequently occurs . It is purpose of this study to report the results of a prospect i ve investigation in patients with subclavian vein catheters . Fifty-two patients admitted to the Istituto Nazionale Tumori of Milan and c and i date to infraclavicular percutaneous catheterization of the subclavian vein were evaluated . There were 26 polyvinyl chloride and 26 rubber silicone catheters , which were correctly positioned in the superior vena cava-atrium . Average duration of the intravenous stay was 12.8 days . Asymptomatic thrombosis was venographically demonstrated in 46.1 % of the polyvinyl chloride catheters and in 11.5 % of the silicone ones ( p = 0.005 ) . The average age of catheters with or without thrombosis was 10.8 and 13.8 days , respectively . Addition of heparin to the infusate ( 1 U/ml ) did not reduce the thrombosis rate in polyvinyl chloride or in silicone catheters , but risk of thrombosis was significantly higher ( p = 0.03 ) in polyvinyl chloride catheters without heparin in comparison to the silicone ones . Osmolarity of the infusional fluid , manipulation during the cannulation , colonization of the catheter tip , and duration of the intravenous stay of the catheter apparently did not influence the rate of thrombosis . Since the natural history of the thrombotic subclavian veins is not known , some caution must be paid to repeat the percutaneous cannulation of the same vein and the change the catheter over a guidewire This prospect i ve , observational and multicentre study assessed the incidence of , and risk factors for ,  symptomatic venous thrombotic complications after central venous catheter ( CVC ) positioning in patients with haematological malignancies . A total of 458 consecutive CVC insertions were registered in 416 patients ( 81·2 % of whom had severe thrombocytopenia ) . Over the observation period ( 3 months or up to catheter removal ) , the incidence of events was : CVC‐related deep vein thrombosis ( DVT ) , 1·5 % ; lower limb DVT , 0·4 % ; pulmonary embolism ( PE ) , 1·3 % ; fatal PE , 0·6 % ; CVC‐related superficial thrombophlebitis , 3·9 % ; CVC‐occlusion/malfunction of thrombotic origin , 6·1 % ; major arterial events , 1·1 % . Severe bleeding and CVC‐related infections were observed in 3·5 % and 4·6 % of cases respectively . A composite end point ( any venous thromboembolism or superficial thrombophlebitis or CVC occlusion/malfunction ) was defined in order to consider venous thrombotic events with a significant impact on clinical practice . With this criterion , the overall incidence was 12·0 % ( 2·54 cases/1000 catheter days ) . No factor helped to predict venous thrombotic complications : only thrombocytopenia was associated with a weak trend for a reduced risk ( odds ratio 0·52 ; 95 % confidence interval 0·26–1·07 ) . No severe bleeding was observed in those patients who received antithrombotic prophylaxis . This study shows that the impact on clinical practice of symptomatic CVC‐related thrombotic complications is not negligible in patients with haematological malignancies A prospect i ve study was carried out to see whether a small fixed dose of warfarin ( 1 mg daily ) given before operation ( mean 20 days ) would prevent deep vein thrombosis in patients having major gynaecological surgery . One hundred and four patients were r and omised into three groups : fixed minidose warfarin ; full dose oral anticoagulation ; and no treatment ( controls ) . There was a significantly lower incidence of deep vein thrombosis in the minidose warfarin and full dose anticoagulant treatment groups ( 9 % ( 3/32 ) and 3 % ( 1/35 ) respectively ) than in the controls ( 30 % ; 11/37 ) but no significant difference between the two anticoagulant treatment groups . Prothrombin time and the activated partial thromboplastin time were normal on the day of surgery in the warfarin treatment group , whereas times were prolonged in the group given full dose anticoagulation . Mean haemoglobin concentrations fell in all three groups after operation but the fall was significantly less in the minidose warfarin treatment group than after full dose anticoagulation . The benefit from full dose oral anticoagulant prophylaxis , based on a preoperative international normalised ratio of 1.5 - 2.5 with rabbit brain Manchester reagent , was similar to the protection achieved in an oral anticoagulant treatment group controlled with human brain Manchester comparative reagent at a similar level of anticoagulation . The lack of disturbance of normal haemostasis at the time of operation together with a significant reduction in deep vein thrombosis may encourage surgeons to introduce minidose prophylaxis with warfarin PURPOSE In this multicenter , r and omized , placebo-controlled clinical trial , we studied whether warfarin 1 mg daily reduces the incidence of symptomatic central venous catheter ( CVC ) -associated thrombosis in patients with cancer . PATIENTS AND METHODS Two hundred fifty-five patients with cancer who required a CVC for at least 7 days were r and omly assigned to receive warfarin 1 mg or placebo . RESULTS There were 11 ( 4.3 % ) symptomatic CVC-associated thromboses among 255 patients , with no difference in the incidence of symptomatic CVC-associated thrombosis between patients taking warfarin 1 mg daily ( six of 130 patients ; 4.6 % ) and patients taking placebo ( five of 125 patients ; 4.0 % ; hazard ratio , 1.20 ; 95 % CI , 0.37 to 3.94 ) . Warfarin had no effect on CVC life span ( 84 days v 63 days in control and warfarin groups , respectively ; 95 % confidence limit , -16 to 55 days ; P = .09 ) , and it did not affect the number of premature CVC removals ( 23.2 % v 25.4 % in control and warfarin groups , respectively ; 95 % confidence limit of difference -8.34 to 12.71 ; P = .68 ) or the frequency of major bleeding episodes ( 2 % v 0 % in control and warfarin groups , respectively ; P = .5 , Fisher 's exact test ) . CONCLUSION Symptomatic CVC-associated thrombosis in patients with cancer , although significant , is less common than previously reported . In this study , the administration of warfarin 1 mg daily did not reduce the incidence of symptomatic CVC-associated thrombosis in patients with cancer . However , the low rate of symptomatic CVC-associated thrombosis means that a much larger trial is required to address this issue definitively OBJECTIVES To compare the complication rate ( bleeding and thrombosis ) of oral anticoagulation in a cohort of patients with cancer to a cohort without cancer . DESIGN Prospect i ve cohort study . SETTING Outpatient anticoagulation clinic in a community hospital . PATIENTS Consecutive patients enrolled in an anticoagulation clinic : 44 with cancer , 64 without cancer . INTERVENTIONS Patients received prophylactic doses of Warfarin ( target INR 2 - 3 in the majority of instances ) and complication rates were assessed . MEASUREMENTS Major bleeding ( strictly defined ) , minor bleeding , recurrent thrombosis , proportion of time with therapeutic INR , frequency of clinic visits . RESULTS The rates of major bleeding , minor bleeding , and recurrent thrombosis were not statistically significantly different in the two groups of patients . Therapeutic INR 's were more difficult to sustain in the cancer patients as compared to the non-cancer patients ( 43.3 % vs 56.9 % , p < 0.0001 ) . There was a non significant trend towards more frequent monitoring for the cancer patients compared with the non-cancer patients ( 4.6 vs 3.5 visits per treatment month , p = 0.14 ) . CONCLUSIONS Oral anticoagulation is safe and effective in the patient with cancer . It is more difficult to sustain a therapeutic INR in the cancer patients and they may need more frequent monitoring to achieve a low complication rate We performed a prospect i ve study in 86 consecutive patients with central vein catheter-related deep venous thrombosis ( DVT ) of the upper extremity , to evaluate the prevalence of  pulmonary embolism ( PE ) , and to identify clinical variables that would increase the likelihood of developing PE in an individual patient . Since upper-extremity DVT was established , all patients received intravenous heparin therapy . Then , a ventilation-perfusion lung scan was obtained within 24 h of DVT diagnosis , whether respiratory symptoms were present or not . Six points of clinical information were recorded on entering in the study , and then compared with the scintigraphic findings : age , sex , the underlying disease , the catheter material , the character of the infusate , and the duration of cannulation . Thirteen patients were considered to have PE . Sixty-six patients were finally classified as having a normal lung scan , and 7 patients were excluded from the study ( because of indeterminate lung scan 6 ; because of femoropopliteal thrombosis simultaneously present 1 ) . Two out of the 13 patients with PE subsequently died because of recurrent , massive embolism , despite adequate heparin therapy . PE was more commonly present in patients with polyvinyle chloride or polyethylene catheters ( 10/38 , 26 % ) as compared to patients with either polyurethane or siliconized catheters ( 3/41 , 7 % ; p < 0.05 , Chi-Square test ; Odds Ratio = 4.52 , 95 % CI 1.01 - 23.07 ) . We conclude that PE is not a rare event in these patients , and it may be life-threatening even despite adequate heparin therapy . ( ABSTRACT TRUNCATED AT 250 WORDS We present a prospect i ve analysis of the insertion complications and longevity of 949 cuffed , tunnelled central venous catheters used for ambulatory chemotherapy . Mean catheter life span was 121.8 days , 13.4 % had complications at insertion , 17.7 % had complications not necessitating removal and 18.6 % had complications requiring removal . The more experienced operators had fewer complications inserting catheters ( P < 0.0001 ) . Late-onset shoulder pain occurred in 4.8 % and was associated with an increased incidence of venous thrombosis ( P < 0.0001 ) and infection ( P = 0.06 ) . Complications necessitating removal were not predicted by patient ' age , site of insertion or malignancy , chemotherapy regimen , insertion platelet and fibrinogen counts , insertion complications , leucocyte count or cuff distance from the exist site . Catheters inserted with their tip in the superior vena cava were more at risk of removal ( 2.57 times ) than those in the right atrium ( P = 0.003 ) Abstract Background : Tunneled venous access devices ( VADs ) are often essential in the care of patients with advanced malignancies , but they carry an uncertain risk of thrombosis . Methods : To determine the incidence of ven 
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On the basis of this evidence , we conclude that there is no proven role for using such thromboprophylaxis .