***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 a population -based study , disease progression and survival were evaluated in untreated patients with newly diagnosed cancer of the prostate without distant metastases . Complete follow-up was achieved in 223 of 227 ( 98 % ) consecutively diagnosed , eligible patients of all ages . After 5 years , the cumulative progression-free survival ( with 95 % confidence interval ) was 71.8 (65.5 - 78.1)% and survival corrected for causes of death other than prostatic cancer was 93.8 (88.3 - 97.6)% . Univariate and multivariate analyses showed no association between age at diagnosis and the natural course . Local progression was less common in localised , non-palpable tumours than in larger tumours . The rate of progression was 18.7 ( 6.1 - 57.1 ) times higher and that of disease-specific death 216.0 ( 31.2 - 1496 ) times higher in patients with poorly than in those with highly differentiated tumours . It is concluded that tumour grade at diagnosis is an excellent predictor of local and distant progression . The low death rate , especially in patients with highly and moderately differentiated tumours , means that any local or systemic therapy intended for patients with early prostatic cancer must be evaluated in clinical trials with untreated controls for comparison Active surveillance followed by selective treatment for men who have evidence of disease progression may be an option for select patients with early‐stage prostate cancer . In this article , the authors report their experience in a contemporary cohort of men with prostate cancer who were managed with active surveillance BACKGROUND In 2008 , we reported that radical prostatectomy , as compared with watchful waiting , reduces the rate of death from prostate cancer . After an additional 3 years of follow-up , we now report estimated 15-year results . METHODS From October 1989 through February 1999 , we r and omly assigned 695 men with early prostate cancer to watchful waiting or radical prostatectomy .  Follow-up was complete through December 2009 , with histopathological review of biopsy and radical-prostatectomy specimens and blinded evaluation of causes of death . Relative risks , with 95 % confidence intervals , were estimated with the use of a Cox proportional-hazards model . RESULTS During a median of 12.8 years , 166 of the 347 men in the radical-prostatectomy group and 201 of the 348 in the watchful-waiting group died ( P=0.007 ) . In the case of 55 men assigned to surgery and 81 men assigned to watchful waiting , death was due to prostate cancer . This yielded a cumulative incidence of death from prostate cancer at 15 years of 14.6 % and 20.7 % , respectively ( a difference of 6.1 percentage points ; 95 % confidence interval [ CI ] , 0.2 to 12.0 ) , and a relative risk with surgery of 0.62 ( 95 % CI , 0.44 to 0.87 ; P=0.01 ) . The survival benefit was similar before and after 9 years of follow-up , was observed also among men with low-risk prostate cancer , and was confined to men younger than 65 years of age . The number needed to treat to avert one death was 15 overall and 7 for men younger than 65 years of age . Among men who underwent radical prostatectomy  , those with extracapsular tumor growth had a risk of death from prostate cancer that was 7 times that of men without extracapsular tumor growth ( relative risk , 6.9 ; 95 % CI , 2.6 to 18.4 ) . CONCLUSIONS Radical prostatectomy was associated with a reduction in the rate of death from prostate cancer . Men with extracapsular tumor growth may benefit from adjuvant local or systemic treatment . ( Funded by the Swedish Cancer Society and the National Institutes of Health . ) OBJECTIVES Outcome data from a prospect i ve study of active surveillance of localised prostate cancer were analysed to identify factors , present at the time of diagnosis , that predict subsequent radical treatment . METHODS Eligible patients had clinical stage T1-T2a , N0-Nx , M0-Mx adenocarcinoma of the prostate with serum PSA<15 ng/ml , Gleason score < or= 7 , primary Gleason grade < or= 3 , and % positive biopsy cores ( pbc ) < or= 50 % . Monitoring included  serial PSA measurement and repeat prostate biopsies . Radical treatment was initiated in the event of biochemical progression ( PSA velocity > 1 ng/ml/yr ) or histological progression ( primary Gleason grade > or= 4 , or % pbc > 50 % ) . Multivariate Cox regression analysis of baseline variables was performed with respect to time to radical treatment . RESULTS The 326 men recruited from 2002 to 2006 have been followed for a median of 22 mo . Median age was 67 yr , and median initial PSA ( iPSA ) 6.4 ng/ml . Sixty-five patients ( 20 % ) had deferred radical treatment , 16 ( 5 % ) changed to watchful waiting because of increasing comorbidity , 7 ( 2 % ) died of other causes , and 238 ( 73 % ) remain on surveillance . On multivariate Cox regression analysis , the free/total PSA ratio ( p<0.001 ) and clinical T stage ( p=0.006 ) were independent determinants of time to radical treatment . CONCLUSIONS In addition to established prognostic factors , the free/total PSA ratio may predict time to radical treatment in patients with untreated , localised prostate cancer managed by active surveillance . This possibility warrants further study 
    Output:
    
Interestingly , only limited numbers of patients under active surveillance require additional treatment .
Recent data suggest that delayed treatment does not appear to alter the clinical outcome among those highly selected patients .