***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: Identification of high-risk individuals will facilitate early diagnosis , reduce overall costs , and also improve the current poor survival from lung cancer . The Liverpool Lung Project prospect i ve cohort of 8,760 participants ages 45 to 79 years , recruited between 1998 and 2008 , was followed annually through the hospital episode statistics until January 31 , 2013 . Cox proportional hazards models were used to identify risk predictors of lung cancer incidence . C-statistic was used to assess the discriminatory accuracy of the models . Models were internally vali date d using the bootstrap method . During mean follow-up of 8.7 years , 237 participants developed lung cancer . Age [ hazard ratio ( HR ) , 1.04 ; 95 % confidence interval ( CI ) , 1.02–1.06 ] , male gender ( HR , 1.48 ; 95 % CI , 1.10–1.98 ) , smoking duration ( HR , 1.04 ; 95 % CI , 1.03–1.05 ) , chronic obstructive pulmonary disease ( HR , 2.43 ; 95 % CI , 1.79–3.30 ) , prior diagnosis of malignant tumor ( HR , 2.84 ; 95 % CI , 2.08–3.89 ) , and early onset of family history of lung cancer ( HR , 1.68 ; 95 % CI , 1.04–2.72 ) were associated with the incidence of lung cancer . The LLPi risk model had a good calibration ( goodness-of-fit χ2 7.58 , P = 0.371 ) . The apparent C-statistic was 0.852 ( 95 % CI , 0.831–0.873 ) and the optimism-corrected bootstrap resampling C-statistic was 0.849 ( 95 % CI , 0.829–0.873 ) . The LLPi risk model may assist in identifying individuals at high risk of developing lung cancer in population -based screening programs . Cancer Prev Res ; 8(6 ) ; 570–5 . © 2015 AACR BACKGROUND Although there is no proven benefit associated with screening for lung cancer , screening programs are attracting many individuals who perceive themselves to be at high risk due to smoking . We sought to determine whether the risk of lung cancer varies predictably among smokers . METHODS We used data on 18 172 subjects enrolled in the Carotene and Retinol Efficacy Trial (CARET)-a large , r and omized trial of lung cancer prevention-to derive a lung cancer risk prediction model . Model inputs included the subject 's age , sex , asbestos exposure history , and smoking history . We assessed the model 's calibration by comparing predicted and observed rates of lung cancer across risk deciles and vali date d it by assessing the extent to which a model estimated on data from five CARET study sites could predict events in the sixth study site . We then applied the model to evaluate the risk of lung cancer among smokers enrolled in a study of lung cancer screening with computed tomography ( CT ) .  RESULTS The model was internally valid and well calibrated . Ten-year lung cancer risk varied greatly among participants in the CT study , from 15 % for a 68-year-old man who has smoked two packs per day for 50 years and continues to smoke , to 0.8 % for a 51-year-old woman who smoked one pack per day for 28 years before quitting 9 years earlier . Even among the subset of CT study participants who would be eligible for a clinical trial of cancer prevention , risk varied greatly . CONCLUSIONS The risk of lung cancer varies widely among smokers . Accurate risk prediction may help individuals who are contemplating voluntary screening to balance the potential benefits and risks . Risk prediction may also be useful for research ers design ing clinical trials of lung cancer prevention STUDY OBJECTIVES To develop and vali date a model for estimating the risk of lung cancer death  in current and former smokers . The model is intended for use in analyzing a population of subjects who are undergoing lung cancer screening or receiving lung cancer chemoprevention  , to determine whether the intervention has altered lung cancer mortality . DESIGN / SETTING / PATIENTS Model derivation was based on analyses of the placebo arm of the Carotene and Retinol Efficacy Trial . Model validation was based on analyses of three other longitudinal cohorts . MEASUREMENTS Observed and predicted number of deaths due to lung cancer . RESULTS In internal validation , the model was highly concordant and well calibrated . In external validation , the model predictions were similar to what was observed in all of the validation analyses . The predicted and observed deaths within 6 years were very similar when assessed in the Johns Hopkins Hospital trial of chest radiography and sputum cytology screening ( 176 predicted , 184 observed , p = 0.53 ) , the Memorial Sloan-Kettering Cancer Center trial of chest radiography and sputum cytology screening ( 108 predicted , 114 observed , p = 0.57 ) , and the National Health and Nutrition Evaluation Survey part I ( 24 predicted , 21 observed , p = 0.52 ) . CONCLUSIONS The number of lung cancer deaths in a population of current or former smokers can be accurately predicted , making model-based evaluations of prevention and early detection interventions a useful adjunct to definitive r and omized trials . We illustrate this potential use with a small example Background : This prospect i ve cohort study aim ed to identify symptom and patient factors that influence time to lung cancer diagnosis and stage at diagnosis . Methods : Data relating to symptoms were collected from patients upon referral with symptoms suspicious of lung cancer in two English regions ; we also examined primary care and hospital records for diagnostic routes and diagnoses . Descriptive and regression analyses were used to investigate associations between symptoms and patient factors with diagnostic intervals and stage . Results : Among 963 participants , 15.9 % were diagnosed with primary lung cancer , 5.9 % with other thoracic malignancies and 78.2 % with non-malignant conditions . Only half the cohort had an isolated first symptom ( 475 , 49.3 % ) ; synchronous first symptoms were common . Haemoptysis , reported by 21.6 % of cases , was the only initial symptom associated with cancer . Diagnostic intervals were shorter for cancer than non-cancer diagnoses ( 91 vs 124 days , P=0.037 ) and for late-stage than early-stage cancer ( 106 vs 168 days , P=0.02 ) . Chest/shoulder pain was the only first symptom with a shorter diagnostic interval for cancer compared with non-cancer diagnoses ( P=0.003 ) . Conclusions : Haemoptysis is the strongest symptom predictor of lung cancer but occurs in only a fifth of patients . Programmes for expediting earlier diagnosis need to focus on multiple symptoms and their evolution The epidemiology of lung cancer is changing in many parts of the world . In the industrialized countries , there is a trend that the incidence in men is declining , while it is increasing for women . Also , adenocarcinomas are becoming relatively more common , especially among men . The purpose of this study was to investigate whether such trends also occur in Sweden and also to describe other aspects of an unselected lung cancer material today , such as symptoms , stage and smoking habits . In the county of Gaevleborg , Sweden , practically all patients with lung cancer are referred to the lung department , and thus a total material of lung cancer patients with only a minimal selection bias can be studied . All patients with lung cancer in the county from January 1 , 1997 to December 31 , 1999 , were investigated prospect ively regarding stage , type of cancer , and symptoms . In all , there were 364 patients , 237 ( 65.1 % ) men and 127 ( 34.9 % ) women . The mean age for men was 69.8 and for women , 68.1 years . 91.9 % of the men and 78.6 % of the women were smokers or ex-smokers . In general the men were heavier smokers than were the women ( P<0.0001 ) . Adenocarcinoma was the most common subtype found in women and squamous cell carcinoma in men . The excess of adenocarcinoma in women was due to never-smoking women ; for smoking and ex-smoking men and women , the proportion of adenocarcinomas was the same . In all , 240 patients ( 68.0 % ) were diagnosed at Stage IIIb ( 27.2 % ) or IV ( 40.8 % ) , with no significant differences between the sexes . The most common first symptom was cough . Only 7.0 % of patients were asymptomatic . In conclusion , the trend of an increasing proportion of adenocarcinoma in lung cancer is seen also in Sweden . A depressingly high percentage of patients present in late stages and are thus inoperable 
    Output:
    
The positive predictive value ( PPV ) of diagnostic symptoms depends on an individual 's prior risk of lung cancer , as well as their presenting symptom pattern .