***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: Prognosis studies are investigations of future events or the evaluation of associations between risk factors and health outcomes in population s of patients ( 1 ) . The results of such studies improve our underst and ing of the clinical course of a disease and assist clinicians in making informed decisions about how best to manage patients . Prognostic research also informs the design of intervention studies by helping define subgroups of patients who may benefit from a new treatment and by providing necessary information about the natural history of a disorder ( 2 ) . There has recently been a rapid increase in the use of systematic review methods to synthesize the evidence on research questions related to prognosis . It is essential that investigators conducting systematic review s thoroughly appraise the method ologic quality of included studies to be confident that a study 's design , conduct , analysis , and interpretation have adequately reduced the opportunity for bias ( 3 , 4 ) . Caution is warranted , however , because inclusion of method ologically weak studies can threaten the internal validity of a systematic review ( 4 ) . This follows abundant empirical evidence that inadequate attention to biases can cause invalid results and inferences ( 5 - 9 ) . However , there is limited consensus on how to appraise the quality of prognosis studies ( 1 ) . A useful framework to assess bias in such studies follows the basic principles of epidemiologic research ( 10 , 11 ) . We focus on 6 areas of potential bias : study participation , study attrition , prognostic factor measurement , confounding measurement and account , outcome measurement , and analysis . The main objectives of our review of review s are to describe methods used to assess the quality of prognosis studies and to describe how well current practice s assess potential biases . Our secondary objective is to develop recommendations to guide future quality appraisal , both within single studies of prognostic factors and within systematic review s of the evidence . We hope this work facilitates future discussion and research on biases in prognosis studies and systematic review s. Methods Literature Search and Study Selection We identified systematic review s of prognosis studies by search ing MEDLINE ( 1966 to October 2005 ) using the search strategy recommended by McKibbon and colleagues ( 12 ) . This strategy combines broad search terms for systematic review s ( systematic review .mp ; meta- analysis .mp ) and a sensitive search strategy for prognosis studies ( cohort , incidence , mortality , follow-up studies , prognos * , predict * , or course ) . We also search ed the reference lists of included review s and method ologic papers to identify other relevant publications . We restricted our search to English- language publications . One review er conducted the search and selected the studies . Systematic review s , defined as review s of published studies with a comprehensive search and systematic selection , were included if they assessed the method ologic quality of the included studies by using 1 or more explicit criteria . We excluded studies if they were meta-analyses of independent patient data only , if their primary goal was to investigate the effectiveness of an intervention or specific diagnostic or screening tests , or if they included studies that were not done on humans . Data Extraction and Synthesis Individual items included in the quality assessment of the systematic review s were recorded as they were reported in the publication ( that is , the information that would be available to readers and future review ers ) . We review ed journal Web sites and contacted the authors of the systematic review s for additional information when authors made such an offer in their original papers . When review s assessed different study design s by using different sets of quality items , we extracted only those items used to assess cohort studies . We constructed a comprehensive list of distinct items that the review s used to assess the quality of their included studies . The full text of each review was screened . All items used by the review authors to assess the quality of studies were extracted into a computerized spreadsheet by 1 review er . Two experienced review ers , a clinical epidemiologist and an epidemiologist , independently synthesized the quality items extracted from the prognosis review s to determine how well the systematic review s assessed potential biases . We did this in 3 steps : 1 ) identified distinct concepts or domains addressed by the quality items ; 2 ) grouped each extracted quality item into the appropriate domain or domains ; and 3 ) identified the domains necessary to assess potential biases in prognosis studies . We then used this information to assess how well the review s ' quality assessment included items from the domains necessary to assess potential biases . After completing each of the first 3 steps , the review ers met to attempt to reach a consensus . The consensus process involved each review er presenting his or her observations and results , followed by discussion and debate . A third review er was available in cases of persistent disagreement or uncertainty . In the first step , all domains addressed by the quality items were identified . The first review er iteratively and progressively defined the domains as items were extracted from the included review s. The second review er defined domains from a r and om list of all extracted quality items . Limited guidance was provided to the review ers so that their assessment s and definitions of domains would be independent . The review ers agreed on a final set of domains that adequately and completely defined all of the extracted items . In the second step , review ers independently grouped each extracted item into the appropriate domains . Review ers considered each extracted item by asking , What is each particular quality item addressing ? or What are the review 's authors getting at with the particular quality assessment item ? . Items were grouped into the domain or domains that best represented the concepts being addressed . For example , the extracted items at least 80 % of the group originally identified was located for follow-up and follow-up was sufficiently complete or does n't jeopardize validity were each independently classified by both review ers as assessing the domain completeness of follow-up adequate , whereas the extracted item quantification and description of all subjects lost to follow-up was classified as assessing the domain completeness of follow-up described . In the third step , we identified the domains necessary to assess potential biases . Each review er considered the ability of the identified domains to adequately address , at least in part , 1 of the following 6 potential biases : 1 ) study participation , 2 ) study attrition , 3 ) prognostic factor measurement , 4 ) confounding measurement and account , 5 ) outcome measurement , and 6 ) analysis . Domains were considered to adequately address part of the framework if information garnered from that domain would inform the assessment of potential bias . For example , both review ers judged that the identified domain study population represents source population or population of interest assessed potential bias in a prognosis study , whereas the domain research question definition did not , although the latter is an important consideration in assessing the inclusion of studies in a systematic review . Finally , on the basis of our previous ratings , we looked at whether each review included items from the domains necessary to assess the 6 potential biases . We calculated the frequency of systematic review s by assessing each potential bias and the number of review s that adequately assessed bias overall . From this systematic synthesis , we developed recommendations for improving quality appraisal in future systematic review s of prognosis studies . We used Microsoft Access and Excel 2002 ( Microsoft Corp. , Redmond , Washington ) for data management and SAS for Windows , version 9.1 ( SAS Institute , Inc. , Cary , North Carolina ) for descriptive statistics . Role of the Funding Sources The funding sources , the Canadian Institutes of Health Research , the Canadian Chiropractic Research Foundation , the Ontario Chiropractic Association , and the Ontario Ministry of Health and Long Term Care , did not have a role in the collection , analysis , or interpretation of the data or in the decision to su bmi t the manuscript for publication . Results We identified 1384 potentially relevant articles . Figure 1 shows a flow chart of studies that were included and excluded . Figure 2 shows the number of review s identified by year of publication . We excluded 131 systematic review s of prognosis studies that did not seem to include any quality assessment of the included studies ; this represented 44 % of prognosis review s. We included 163 review s of prognosis studies in our analysis ( 13 - 175 ) . The most common topics were cancer ( 15 % ) , musculoskeletal disorders and rheumatology ( 13 % ) , cardiovascular ( 10 % ) , neurology ( 10 % ) , and obstetrics ( 10 % ) . Other review s included a wide range of health and health care topics . Sixty-three percent of the review s investigated the association between a specific prognostic factor and a particular outcome ; the remainder investigated multiple prognostic factors or models . The number of primary studies included in each systematic review ranged from 3 to 167 ( median , 18 [ interquartile range , 12 to 31 ] ) . A complete description of the included review s is available from the authors on request . Figure 1 . Flow diagram of inclusion and exclusion criteria of systematic review s. Figure 2 . Number of systematic review s of prognosis studies identified over time . Quality Items One hundred fifty-three review s provided adequate detail to allow extraction of quality items . Eight hundred eighty-two distinct quality items were extracted from the review s. Most review s developed their own set of quality items , with only a few applying criteria from previous review s. Most quality items BACKGROUND There is currently no st and ard treatment for patients with castration-resistant prostate cancer ( CRPC ) whose disease progresses after docetaxel-based chemotherapy .  The purpose of this study was to prospect ively assess the anticancer activity and tolerance of the carboplatin-etoposide combination in this setting while evaluating neuroendocrine ( NE ) features . PATIENTS AND METHODS Patients with CRPC and metastases who experienced failure after first-line docetaxel-based chemotherapy  were treated with carboplatin ( area under the curve 5 , day 1 ) and etoposide ( 80 mg/m(2)/day from days 1 to 3 ) , repeated every 3 weeks . The association between serum chromogranin A ( CgA ) , neuron-specific enolase ( NSE ) , prostate-specific antigen-doubling time ( PSADT ) , and treatment efficacy was studied . RESULTS Forty patients with CRPC who had received docetaxel with ( n = 20 ) or without ( n = 20 ) estramustine received the  carboplatin-etoposide combination  as second-line chemotherapy . A prostate-specific antigen ( PSA ) response defined as a PSA decline > or = 50 % was achieved in nine patients ( 23 % ) . Median progression-free survival ( PFS ) was 2.1 months ( range 0.6 - 9.6 ) and median overall survival was 19 months ( range 2.1 - 27.7 ) . Pain response was achieved in 15 ( 53 % ) of 28 assessable patients . Toxicity , including mainly grade s 3 - 4 anaemia ( 25 % ) and febrile neutropenia in only 2 % of patients , was manageable . Baseline CgA , NSE , or PSADT were not significant predictors for response or PFS . The PSA response rates were 18 % and 31 % in patients with normal and elevated serum CgA , respectively . It was 25 % and 20 % , respectively , in patients with normal and elevated serum NSE . CONCLUSIONS Combining carboplatin and etoposide as second-line chemotherapy in patients with CRPC is active and well tolerated in spite of a limited PFS . Activity was observed in CRPC with and without NE features The presence of neuroendocrine ( NE ) differentiation in the context of predominantly exocrine prostate cancer may play a key role in and rogen-independent tumor growth . The prognostic significance of  plasma chromogranin A ( CgA )  was assessed in a series of consecutive prostate cancer patients with hormone-refractory disease . One hundred and eight patients with newly diagnosed hormone-refractory prostate cancer entered the study . Plasma CgA levels and other biochemical parameters , such as serum prostate specific antigen , serum alkaline phosphatase , serum lactate dehydrogenase , serum albumin and hemoglobin concentration , were measured at baseline ( i.e. when hormone refractoriness occurred ) and their prognostic role was evaluated together with patient performance status , Gleason score ( at diagnosis of prostate cancer ) and the presence of visceral metastases . Furthermore , plasma CgA  was prospect ively evaluated in 50 patients undergoing chemotherapy .  At baseline , 45 patients ( 43.3 % ) showed elevated CgA values . Plasma CgA negatively correlated with survival , either in univariate analysis ( P=0.008 ) or in multivariate analysis , after adjusting for previously mentioned prognostic parameters ( P<0.05 ) . In the patient subset undergoing chemotherapy , median CgA ( range ) values were 13.3 ( 3.0 - 141.0 ) U/l at baseline , 19.1 ( 3.0 - 486.0 ) U/l after 3 months , 20.8 ( 3.0 - 702.0 ) U/l after 6 months and 39.4 ( 3.0 - 414.0 ) U/l after 9 months ( P<0.01 ) . The corresponding supranormal rates were 17/50 ( 34 % ) , 23/50 ( 46 % ) , 26/50 ( 52 % ) and 34/50 ( 68 % ) respectively ( P<0.005 ) . Elevated plasma CgA levels are frequently observed in prostate cancer patients with hormone-refractory disease and correlate with poor prognosis . NE differentiation in hormone-refractory patients is a time-dependent phenomenon and is not influenced by conventional antineoplastic treatments Objectives : Favorable phase I results justified this pilot phase II study to assess the efficacy of docetaxel/curcumin in patients with chemotherapy-naive metastatic castration-resistant prostate cancer ( CRPC ) . Methods : Thirty patients with progressing CRPC and a rising prostate-specific antigen ( PSA ) received docetaxel/prednisone in st and ard conditions for 6 cycles in combination with per os curcumin , 6,000 mg/day ( day -4 to day + 2 of docetaxel ) . The co- primary endpoint was the overall response rate determined by PSA and target assessment s. An ancillary study assessed the seric values of chromogranin A ( Cg 
    Output:
    
After review ing the articles , the major result was that elevated serum NSE  appears to correlate with prognosis in advanced PCa , particularly in patients with progressive and metastatic castration-resistant PCa .