***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: Energy restriction reduces prostate tumor growth in transplantable tumor models in rodents , which suggests that excessive energy intake may contribute to the risk of prostate cancer . The association of total energy intake across the normal range with prostate cancer has not been consistent in epidemiological studies . We prospect ively evaluated the joint associations of energy intake and body size or physical activity with prostate cancer . Participants were 46786 male health professionals ages 40 - 75 years at baseline in 1986 who were free of cancer diagnosis . Between 1986 and 2000 , we documented 2896 incident prostate cancer cases ( excluding stage T1a ) by review of medical records and histopathology reports . Of these , 339 were metastatic or fatal cases . We used Cox proportional hazards regression to estimate the multivariate relative risk ( RR ) of prostate cancer associated with energy intake measured using a food frequency question naire , overall and stratified by body mass index , waist size , physical activity , as well as by age and family history of prostate cancer . There was no association between energy intake and total prostate cancer incidence . However , a modest increased risk of metastatic or fatal disease with energy intake was suggested [ RR comparing extreme quintiles : 1.38 , 95 % confidence interval ( CI ) 0.96 - 1.98 , P(trend ) = 0.06 ] . This association was most pronounced in men with a lower body mass index ( in stratum < 24 kg/m(2 ) : RR = 1.76 , 95 % CI 0.92 - 3.39 ; P(interaction ) = 0.04 ) , smaller waist size [ in stratum < or= 37 inches : RR = 1.91 , 95 % CI 0.83 - 4.36 ; P(interaction ) = 0.03 ] , and who were more physically active [ in stratum > or= median : RR = 1.74 , 95 % CI 0.93 - 3.26 ; P(interaction ) = 0.09 ] . Also , the association of energy intake with metastatic and fatal prostate cancer was restricted to men who were younger [ in stratum < or= 65 years old : RR = 2.60 , 95 % CI 1.26 - 5.39 ; P(interaction ) = 0.04 ] or who had a positive family history [ RR = 3.33 , 95 % CI 1.26 - 8.76 ; P(interaction ) = 0.04 ] . Although energy intake is known to be imperfectly measured by question naire , we observed a positive association between energy intake and metastatic or fatal prostate cancer among men  who were leaner , more physically active , younger , and who had a family history of prostate cancer . Our observations suggest the testable hypothesis that the elevated risk of clinical ly important prostate cancer in men with a high  energy intake may be attributable to certain metabolic profiles that favor enhanced growth factor production over an increase in adiposity Background : The possible benefit of lifetime physical activity ( PA ) in reducing prostate cancer incidence and mortality is unclear . Methods : A prospect i ve cohort of 45 887 men aged 45–79 years was followed up from January 1998 to December 2007 for prostate cancer incidence ( n=2735 ) and to December 2006 for its subtypes and for fatal ( n=190 ) prostate cancer . Results : We observed an inverse association between lifetime ( average of age 30 and 50 years , and baseline age ) total PA levels and prostate cancer risk . Multivariate-adjusted incidence in the top quartile of lifetime total PA  decreased by 16 % ( 95 % confidence interval (CI)=2–27 % ) compared with that in the bottom quartile . We also observed an inverse association between average lifetime work or occupational activity and walking or bicycling duration and prostate cancer risk . Compared with men who mostly sit during their main work or occupation , men who sit half of the time experienced a 20 % lower risk ( 95 % CI=7–31 % ) . The rate ratio linearly decreased by 7 % ( 95 % CI=1–12 % ) for total , 8 % ( 95 % CI=0–16 % ) for localised and 12 % ( 95 % CI=2–20 % ) for advanced prostate cancer for every 30 min per day increment of lifetime walking or bicycling in the range of 30 to 120 min per day . Conclusions : Our results suggest that not sitting for most of the time during work or occupational activity and walking or bicycling more than 30 min per day during adult life is associated with reduced incidence of prostate cancer Purpose Vasectomy is a commonly used form of male sterilization , and some studies have suggested that it may be associated with an increased risk of prostate cancer , including more aggressive forms of the disease . We investigated the prospect i ve association of vasectomy with prostate cancer in a large European cohort , with a focus on high- grade and advanced-stage tumors , and death due to prostate cancer . Patients and Methods A total of 84,753 men from the European Prospect i ve Investigation into Cancer and Nutrition ( EPIC ) , aged 35 to 79 years , provided information on vasectomy status ( 15 % with vasectomy ) at recruitment and were followed for incidence of prostate cancer and death . We estimated the association of vasectomy with prostate cancer risk overall , by tumor subtype , and for death due to prostate cancer , using multivariable-adjusted Cox proportional hazards models . Results During an average follow-up of 15.4 years , 4,377 men were diagnosed with prostate cancer , including 641 who had undergone a vasectomy .  Vasectomy  was not associated with prostate cancer risk ( hazard ratio [ HR ] , 1.05 ; 95 % CI , 0.96 to 1.15 ) , and no evidence for heterogeneity in the association was observed by stage of disease or years since vasectomy . There was some evidence of heterogeneity by tumor grade ( P = .02 ) , with an increased risk for low-intermediate grade ( HR , 1.14 ; 95 % CI , 1.01 to 1.29 ) but not high- grade prostate cancer ( HR , 0.83 ; 95 % CI , 0.64 to 1.07 ) .  Vasectomy  was not associated with death due to prostate cancer ( HR , 0.88 ; 95 % CI , 0.68 to 1.12 ) . Conclusion These findings from a large European prospect i ve study show no elevated risk for overall , high- grade or advanced-stage prostate cancer , or death due to prostate cancer in men who have undergone a vasectomy  compared with men who have not Many potentially modifiable risk factors for prostate cancer are also associated with prostate cancer screening , which may induce a bias in epidemiologic studies . We investigated the associations of body mass index ( weight (kg)/height (m)(2 ) ) , smoking , and  alcohol consumption  with risk of fatal prostate cancer in Asian countries where prostate cancer screening is not widely utilized . Analysis included 18 prospect i ve cohort studies conducted during 1963 - 2006 across 6 countries in southern and eastern Asia that are part of the Asia Cohort Consortium .  Body mass index , smoking , and alcohol intake  were determined by question naire at baseline , and cause of death was ascertained through death certificates .  Analysis included 522,736 men aged 54 years , on average , at baseline . During 4.8 million person-years of follow-up , there were 634 prostate cancer deaths ( 367 prostate cancer deaths across the 11 cohorts with alcohol data ) . In Cox proportional hazards analyses of all cohorts in the Asia Cohort Consortium , prostate cancer mortality was not significantly associated with obesity ( body mass index > 25 : hazard ratio ( HR ) = 1.08 , 95 % confidence interval ( CI ) : 0.85 , 1.36 ) , ever smoking ( HR = 1.00 , 95 % CI : 0.84 , 1.21 ) , or heavy alcohol intake ( HR = 1.00 , 95 % CI : 0.74 , 1.35 ) . Differences in prostate cancer screening and detection probably contribute to differences in the association of obesity , smoking , or alcohol intake with prostate cancer risk and mortality between Asian and Western population s and thus require further investigation Prospect i ve epidemiologic studies conducted in Western population s support an association between current smoking and aggressive subtypes of prostate cancer . In Singapore , where prostate-specific antigen is not used for population -wide screening , prostate cancer incidence has tripled within the past two decades . Using Cox regression methods , we examined the relationship between smoking and prostate cancer established between 1993 and 1998 in a cohort of 27,293 Singapore Chinese men . As of December 2006 , 250 incident prostate cancer cases were diagnosed . In our cohort , 42.2 % reported never smoking cigarettes , 15.7 % quit over 5 years ago ( long-term former ) , 5.7 % quit within the past 5 years ( recent former ) , and 36.4 % were current smokers . From multivariable models , we observed no association with smoking status , age at starting to smoke , years smoked , or number of cigarettes per day . Among recent former and current smokers combined , we observed a small positive association for earlier age at starting to smoke that was somewhat stronger for nonadvanced disease ( hazard ratio = 1.63 , 95 % confidence interval : 0.85 , 3.12 , for < 15 years versus nonsmokers ) . Smoking was not a major risk factor for prostate cancer in our Singapore Chinese cohort , a traditionally low risk population with parallel increases in incidence and mortality Vigorous activity after diagnosis was recently reported to be inversely associated with prostate cancer-specific mortality . However , men with metastatic disease may decrease their activity due to their disease ; thus , a causal interpretation is uncertain . We therefore prospect ively examined  vigorous activity and brisk walking  after diagnosis in relation to risk of prostate cancer progression , an outcome less susceptible to reverse causation , among 1,455 men diagnosed with clinical ly localized prostate cancer . Cox proportional hazards regression was used to examine  vigorous activity , nonvigorous activity , walking duration , and walking pace  after diagnosis and risk of prostate cancer progression . We observed 117 events ( 45 biochemical recurrences , 66 secondary treatments , 3 bone metastases , 3 prostate cancer deaths ) during 2,750 person-years .  Walking  accounted for nearly half of all activity . Men who walked briskly for 3 h/wk or more had a 57 % lower rate of progression than men who walked at an easy pace for less than 3 h/wk ( HR = 0.43 ; 95 % CI : 0.21 - 0.91 ; P = 0.03 ) . Walking pace was associated with decreased risk of progression independent of duration ( HR brisk vs. easy pace = 0.52 ; 95 % CI : 0.29 - 0.91 ; P(trend ) = 0.01 ) . Few men engaged in vigorous activity , but there was a suggestive inverse association ( HR ≥3 h/wk vs. none = 0.63 ; 95 % CI : 0.32 - 1.23 ; P(trend ) = 0.17 ) . Walking duration and total nonvigorous activity were not associated with risk of progression independent of pace or vigorous activity , respectively . Brisk walking  after diagnosis may inhibit or delay prostate cancer progression among men diagnosed with clinical ly localized prostate cancer Background : Smoking is not associated with prostate cancer incidence in most studies , but associations between smoking and fatal prostate cancer have been reported . Methods : During 1992 and 2000 , lifestyle information was assessed via question naires and personal interview in a cohort of 145 112 European men . Until 2009 , 4623 incident cases of prostate cancer were identified , including 1517 cases of low- grade , 396 cases of high grade , 1516 cases of localised , 808 cases of advanced disease , and 432 fatal cases . Multivariable Cox proportional hazards regression models were used to examine the association of smoking status , smoking intensity , and smoking duration with the risk of incident and fatal prostate cancer . Results : Compared with never smokers , current smokers had a reduced risk of prostate cancer ( RR=0.90 , 95 % CI : 0.83–0.97 ) , which was statistically significant for localised and low- grade disease , but not for advanced or high- grade disease . In contrast , heavy smokers ( 25 + cigarettes per day ) and men who had smoked for a long time ( 40 + years ) had a higher risk of prostate cancer death ( RR=1.81 , 95 % CI : 1.11–2.93 ; RR=1.38 , 95 % CI : 1.01–1.87 , respectively ) . Conclusion : The observation of an increased prostate cancer mortality among heavy smokers confirms the results of previous prospect i ve studies Background : Health behaviour changes may improve the quality of life and survival among cancer survivors . We prospect ively examined changes in health behaviour among and between men with prostate cancer ( PC ) , men with cancers other than PC and cancer-free men . Methods : We analysed data for 20 914 men ( 50–65 years ) , 426 with cancer , and 20 488 persons who were cancer-free between baseline ( 1993–1997 ) and follow-up ( 2 
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EVIDENCE SYNTHESIS While data concerning the impact of smoking on PCa development remain conflicting , there is robust evidence that smoking is associated with aggressive tumor features and worse cancer-related outcome , which seems to be maintained for 10 yr after smoking cessation .
Less convincing and limited evidence exists for the association of sexual activity with PCa risk .
The findings related to PA and PCa support the inference that exercise might be a useful factor in the prevention of PCa and tumor progression , while it is not finally proved under which specific conditions PA might be protective against disease development .
As several studies indicate a positive impact of exercise on tumor development , progression , and treatment outcome , it is certainly reasonable to advocate an active lifestyle .
While the evidence for sexual activity is not overall clear , we found that smoking might lead to more aggressive cancers and result in worse treatment outcome .
Physical activity might prevent prostate cancer and improve cancer-related outcomes as well .