Case-control study of prostate cancer and socioeconomic factors

Physical activity in relation to risk of prostate cancer: a systematic review and meta-analysis

Background

Prostate cancer (PCa) is one of the most common cancers among men, yet little is known about its modifiable risk and protective factors. This study aims to quantitatively summarize observational studies relating physical activity (PA) to PCa incidence and mortality.

Materials and methods

Published articles pertaining to PA and PCa incidence and mortality were retrieved in July 2017 using the Medline and EMBASE databases. The literature review yielded 48 cohort studies and 24 case-control studies with a total of 151 748 PCa cases. The mean age of the study participants at baseline was 61 years.

Results

In random-effects models, comparing the highest versus the lowest level of overall PA showed a summary relative risk (RR) estimate for total PCa incidence close to the null [RR = 0.99, 95% confidence interval (CI) = 0.94-1.04]. The corresponding RRs for advanced and non-advanced PCa were 0.92 (95% CI = 0.80-1.06) and 0.95 (95% CI = 0.85-1.07), respectively. We noted a statistically significant inverse association between long-term occupational activity and total PCa (RR = 0.83, 95% CI = 0.71-0.98, n studies = 13), although that finding became statistically non-significant when individual studies were removed from the analysis. When evaluated by cancer subtype, an inverse association with long-term occupational activity was noted for non-advanced/non-aggressive PCa (RR = 0.51, 95% CI = 0.37-0.71, n studies = 2) and regular recreational activity was inversely related to advanced/aggressive PCa (RR = 0.75, 95% CI = 0.60-0.95, n studies = 2), although these observations are based on a low number of studies. Moreover, PA after diagnosis was related to reduced risk of PCa mortality among survivors of PCa (summary RR based on four studies = 0.69, 95% CI = 0.55-0.85).

Conclusions

Whether PA protects against PCa remains elusive. Further investigation taking into account the complex clinical and pathologic nature of PCa is needed to clarify the PA and PCa incidence relation. Moreover, future studies are needed to confirm whether PA after diagnosis reduces risk of PCa mortality.

Disadvantageous Socioeconomic Position at Specific Life Periods May Contribute to Prostate Cancer Risk and Aggressiveness

Background: Previous studies on socioeconomic position (SEP) and risk of prostate cancer (PCa) have produced contradictory results. Most measured SEP only once during the individuals' life span. The aim of the study was to identify life course models that describe best the relationship between SEP measured during childhood/adolescence, early- and late-adulthood, and risk of PCa overall as well as according to tumor aggressiveness at diagnosis. Methods: We used data from a population-based case-control study of PCa conducted in the predominantly French-speaking population in Montreal, Canada. Cases (n = 1,930) with new, histologically-confirmed PCa were ascertained across hospitals deserving the French-speaking population in 2005-2009. Controls (n = 1,991), selected from Quebec's list of French-speaking electors, were frequency-matched to cases (±5 years). In-person interviews collected information on socio-demographic and lifestyle characteristics, and a complete occupational history. Measures of SEP during childhood/adolescence included parents' ownership of a car and father's longest occupation, while the subject's first and longest occupations were used to indicate early- and late-adulthood SEP, respectively. We used the Bayesian relevant life course exposure model to investigate the relationship between lifelong SEP and PCa risk. Results: Cumulative exposure to disadvantageous SEP was associated with about a 50% increase in odds of developing PCa. Late-adulthood SEP was identified as a sensitive period for aggressive PCa. Childhood/adolescence SEP based on parents' ownership of a car was associated with non-aggressive PCa. Associations were independent from PCa screening. Conclusion: Disadvantageous SEP over the life course was associated with higher PCa incidence, with consistent evidence of sensitive time periods for cancer aggressiveness. The mechanisms through which disadvantageous SEP relates to PCa risk need to be further elucidated.

Physical Activity and Prostate Cancer: An Updated Review

Prostate cancer affects a major proportion of older men, and effective preventive measures are few. Earlier suggestions of 10-30% risk reduction from vigorous physical activity thus merit further analysis. This narrative review updates information on associations between physical activity and prostate cancer, seeking activity patterns associated with maximal risk reduction. Systematic searches of Ovid/MEDLINE and PubMed databases from 1996 to June 2016 have linked the terms prostate neoplasms/prostate cancer with occupation, occupational title, sedentary job or heavy work, exercise, physical activity, sports, athletes, physical education/training or aerobic fitness. Combining these searches with findings from earlier reviews, 85 analyses were captured, although three were repeat analyses of the same data set. Seven analyses reported increased risk, and a further 31 showed no clear relationship. However, 24 analyses found a trend to diminished risk, and 21 a significant decrease (10-30% or more) in at least some subject subsets. Benefit was seen more consistently in occupational than in leisure studies, usually with adolescence or the early 20 s as the optimal age for preventive activity. In general, benefit showed a dose-response relationship, with vigorous activity required for maximal effect. Furthermore, several recent observational studies have indicated that physical activity is beneficial in preventing disease recurrence and improving survival following the diagnosis and treatment of prostate cancer. Despite continued research, conclusive proof of an association between regular physical activity and a low risk of prostate cancer remains elusive. However, reports that exercise exacerbates risk are few, and despite issues around controls, covariates, and co-morbidities, an impressive number of studies have now found significant benefit, suggesting that regular physical activity is important in terms of disease development, progression, and therapy. Given also the many other health benefits of an active lifestyle, it can be recommended as a potentially useful measure in the prevention of prostate cancer.

An epidemiological analysis of potential associations between C-reactive protein, inflammation, and prostate cancer in the male US population using the 2009-2010 National Health and Nutrition Examination Survey (NHANES) data

Prostate cancer is the second leading cause of cancer-related deaths in US males, yet much remains to be learned about the role of inflammation in its etiology. We hypothesized that preexisting exposure to chronic inflammatory conditions caused by infectious agents or inflammatory diseases increase the risk of prostate cancer. Using the 2009-2010 National Health and Nutrition Examination Survey, we examined the relationships between demographic variables, inflammation, infection, circulating plasma C-reactive protein (CRP), and the risk of occurrence of prostate cancer in US men over 18 years of age. Using IBM SPSS, we performed bivariate and logistic regression analyses using high CRP values as the dependent variable and five study covariates including prostate cancer status. From 2009-2010, an estimated 5,448,373 men reported having prostate cancer of which the majority were Caucasian (70.1%) and were aged 40 years and older (62.7%). Bivariate analyses demonstrated that high CRP was not associated with an increased risk of prostate cancer. Greater odds of having prostate cancer were revealed for men that had inflammation related to disease (OR = 1.029, CI 1.029-1.029) and those who were not taking drugs to control inflammation (OR = 1.330, CI 1.324-1.336). Men who did not have inflammation resulting from non-infectious diseases had greater odds of not having prostate cancer (OR = 1.031, CI 1.030-1.031). Logistic regression analysis yielded that men with the highest CRP values had greater odds of having higher household incomes and lower odds of having received higher education, being aged 40 years or older, being of a race or ethnicity different from other, and of having prostate cancer. Our results show that chronic inflammation of multiple etiologies is a risk factor for prostate cancer and that CRP is not associated with this increased risk. Further research is needed to elucidate the complex interactions between inflammation and prostate cancer.

Smoking at diagnosis and survival in cancer patients

The effect of smoking on survival in cancer patients is limited by the lack of structured prospective assessments of smoking at diagnosis. To assess the effect of smoking at diagnosis on survival, structured smoking assessments were obtained in a cohort of 5,185 cancer patients within 30 days of a cancer diagnosis between 1982 and 1998. Hazard ratios (HRs) or odds ratios were generated to analyze the effects of smoking at diagnosis on overall mortality (OM) and disease-specific mortality (DSM) in a patient cohort from 13 disease sites containing at least 100 patients in each disease site. With a minimum of 12 years of follow-up, current smoking increased OM risk versus recent quit (HR 1.17), former (HR 1.29) and never smokers (HR 1.38) in the overall cohort. Current smoking increased DSM risk versus former (HR 1.23) and never smokers (HR 1.18). In disease sites with proportionately large (>20%) recent quit cohorts (lung and head/neck), current smoking increased OM and DSM risks as compared with recent quit. Current smoking increased mortality risks in lung, head/neck, prostate and leukemia in men and breast, ovary, uterus and melanoma in women. Current smoking was not associated with any survival benefit in any disease site. Data using prospective structured smoking assessments demonstrate that current smoking increased long-term OM and DSM. Standardized smoking assessment at diagnosis is an important variable for evaluating outcomes in cancer patients.

Does physical activity reduce the risk of prostate cancer? A systematic review and meta-analysis

CONTEXT

Numerous observational epidemiologic studies have evaluated the association between physical activity and prostate cancer (PCa); however, the existing results are inconsistent.

OBJECTIVE

To determine the association between physical activity and risk of PCa.

EVIDENCE ACQUISITION

A systematic search was performed using the Medline, Embase, and Web of Science databases through 15 May 2011 to identify all English-language articles that examined the effect of physical activity on the risk of PCa. This meta-analysis was conducted according to the guidelines for the meta-analysis of observational studies in epidemiology.

EVIDENCE SYNTHESIS

This meta-analysis consisted of 88,294 cases from 19 eligible cohort studies and 24 eligible case-control studies. When data from both types of studies were combined, total physical activity (TPA) was significantly associated with a decreased risk of PCa (pooled relative risk [RR]: 0.90; 95% confidence interval [CI], 0.84-0.95). The pooled RR for occupational physical activity (OPA) and recreational physical activity (RPA) were 0.81 (95% CI, 0.73-0.91) and 0.95 (95% CI, 0.89-1.00), respectively. Notably, for TPA, we observed a significant PCa risk reduction for individuals between 20 and 45 yr of age (RR: 0.93; 95% CI, 0.89-0.97) and between 45 and 65 yr of age (RR: 0.91; 95% CI, 0.86-0.97) who performed activities but not for individuals <20 yr of age or >65 yr of age.

CONCLUSIONS

There appears to be an inverse association between physical activity and PCa risk, albeit a small one. Given that increasing physical activity has numerous other health benefits, men should be encouraged to increase their physical activity in both occupational and recreational time to improve their overall health and potentially decrease their risk of PCa.

A review of African American-white differences in risk factors for cancer: prostate cancer

OBJECTIVE

African American men have higher prostate cancer incidence rates than White men, for reasons not completely understood. This review summarizes the existing literature of race-specific associations between risk factors and prostate cancer in order to examine whether associations differ.

METHODS

We reviewed epidemiologic studies published between January 1970 and December 2008 that reported race-specific effect estimates. We focused mainly on modifiable risk factors related to lifestyle and health. A total of 37 articles from 21 study populations met our inclusion criteria.

RESULTS

We found no evidence of racial differences in associations between prostate cancer and alcohol intake, tobacco use, and family history of prostate cancer. Research suggests that a modest positive association may exist between height and prostate cancer risk (all prostate cancer and advanced prostate cancer) among Whites only. No clear patterns were observed for associations with physical activity, weight/body mass index, dietary factors, occupational history, sexual behavior, sexually transmissible infections, and other health conditions.

DISCUSSION

Our results suggest few differences in prostate cancer risk factors exist between racial groups and underscore areas where additional research is needed. Future studies should enroll higher numbers of African American participants and report results for advanced prostate cancer.

Physical activity and genitourinary cancer prevention

The present review of epidemiologic studies of physical activity and genitourinary cancers (prostate, bladder, renal cell, and testicular cancers) suggests a weak inverse relation of physical activity to risk of prostate and renal cell cancer, with average risk decreases of less than 10% comparing high versus low levels of physical activity. For prostate cancer, studies that assessed activity intensity or those that considered fatal prostate cancer as a study endpoint produced the strongest inverse association. For renal cell cancer, the inverse relation with physical activity was more apparent among women than men, among normal weight than overweight or obese individuals, and among older than younger individuals. In contrast to prostate and renal cell cancer, available data show that physical activity is not associated with bladder or testicular cancer. Future research should include improvements in self-reported activity measures and incorporation of objective assessments of physical activity over the life course in order to more precisely characterize types, parameters, and timing of physical activity in relation to genitourinary cancers. Also, data are lacking regarding whether fitness potentially influences genitourinary cancer risk. The relation of physical activity and fitness to genitourinary cancer prognosis and survival requires specific attention. Mechanistic research should identify the underlying biologic pathways potentially linking physical activity to genitourinary cancers.

Age-specific physical activity and prostate cancer risk among white men and black men

BACKGROUND

: The relation of physical activity across the lifespan to risk of prostate cancer has not been thoroughly investigated, particularly among black men. The authors investigated physical activity, including activity during different age periods and of various intensities, in relation to prostate cancer incidence among white men and black men.

METHODS

: In total, 160,006 white men and 3671 black men ages 51 years to 72 years who were enrolled in the National Institutes of Health-AARP Diet and Health Study reported their time spent per week engaging in physical activity during ages 15 to 18 years, 19 years to 29 years, 35 years to 39 years, and during the past 10 years. Cox regression models were used to examine physical activity, categorized by intensity (moderate or vigorous, light, and total), in relation to prostate cancer risk.

RESULTS

: During 7 years of follow-up, 9624 white men and 371 black men developed prostate cancer. Among white men, physical activity had no association with prostate cancer regardless of age period or activity intensity. Among black men, engaging in > or =4 hours of moderate/vigorous intensity physical activity versus infrequent activity during ages 19 years to 29 years was related to a 35% lower risk of prostate cancer (relative risk, 0.65; 95% confidence interval [95% CI], 0.43-0.99 [P(trend) = .01]). Frequent moderate/vigorous physical activity at ages 35 years to 39 years also potentially was related to reduced prostate cancer risk (relative risk, 0.59; 95% CI, 0.36-0.96 [P(trend) = .15]).

CONCLUSIONS

: Regular physical activity may reduce prostate cancer risk among black men, and activity during young adulthood may yield the greatest benefit. This novel finding needs confirmation in additional studies. Cancer 2009. Published 2009 by the American Cancer Society.

Exercise therapy across the prostate cancer continuum

Exercise has been increasingly investigated as an adjunct therapy for cancer patients. The purpose of this paper is to comprehensively review the literature regarding exercise as a therapeutic adjunct for prostate cancer (PC). Several studies in patients with PC have shown quality of life improvements associated with exercise. Although no study has established the effect of exercise as a monotherapy for PC, the molecular mechanisms responsible for the potential association between exercise and PC are being elucidated. Given the low-risk, high-reward nature of these studies, further investigations are needed to better define the function of exercise along the PC continuum.

Socio-economic status and overall and cause-specific mortality in Sweden

BACKGROUND

Previous studies have reported discrepancies in cause-specific mortality among groups of individuals with different socio-economic status. However, most of the studies were limited by the specificity of the investigated populations and the broad definitions of the causes of death. The aim of the present population-based study was to explore the dependence of disease specific mortalities on the socio-economic status in Sweden, a country with universal health care. Another aim was to investigate possible gender differences.

METHODS

Using the 2006 update of the Swedish Family-Cancer Database, we identified over 2 million individuals with socio-economic data recorded in the 1960 national census. The association between mortality and socio-economic status was investigated by Cox's proportional hazards models taking into account the age, time period and residential area in both men and women, and additionally parity and age at first birth in women.

RESULTS

We observed significant associations between socio-economic status and mortality due to cardiovascular diseases, respiratory diseases, to cancer and to endocrine, nutritional and metabolic diseases. The influence of socio-economic status on female breast cancer was markedly specific: women with a higher socio-economic status showed increased mortality due to breast cancer.

CONCLUSION

Even in Sweden, a country where health care is universally provided, higher socio-economic status is associated with decreased overall and cause-specific mortalities. Comparison of mortality among female and male socio-economic groups may provide valuable insights into the underlying causes of socio-economic inequalities in length of life.

Body size and composition and prostate cancer risk: systematic review and meta-regression analysis

The evidence that measures of obesity and stature are associated with prostate cancer is weak and inconsistent. We performed a systematic review and meta-analysis of the relationship between body mass index (BMI), height, weight, waist circumference and waist-to-hips ratio (WHR) and the risk of prostate cancer. Study-specific dose-response slopes were obtained, and random effects rate ratios (RRs) were computed from linear meta-regression models. We included 55,521 cases identified among 2,818,767 men from 31 cohort studies, and 13,232 cases and 16,317 controls from 25 case-control studies. The overall RR for BMI was 1.05 per 5 kg/m2 increment, 95% CI 1.01-1.08. For studies that reported results by stage of disease, the RRs were stronger for advanced disease (RR 1.12 per 5 kg/m2 increment, 95% CI 1.01-1.23) compared with localized disease (RR 0.96 per 5 kg/m2 increment, 95% CI 0.89-1.03), p = 0.02. Height was also positively associated with risk (RR 1.05 per 10 cm increment, 95% CI 1.02-1.09), but the evidence was weak for weight (RR 1.01 per 10 kg increment, 95% CI 0.97-1.04), waist circumference (RR 1.03 per 10 cm increment, 95% CI 0.99-1.07), and WHR (RR 1.11 per 0.1 unit increment, 95% CI 0.95-1.30). Stronger associations were observed among cohort studies compared with case-control studies for BMI (p = 0.006), height (p < 0.001) and weight (p = 0.02). This meta-analysis indicates that obesity is weakly associated with an increased risk of prostate cancer (particularly advanced stage tumors). While increased stature may also increase risk, there is little evidence for an association with central obesity.

International comparisons of prostate cancer mortality rates with dietary practices and sunlight levels

Prostate cancer mortality rates vary widely across the world. The purpose of this study is to identify environmental factors associated with prostate cancer mortality risk. Prostate cancer mortality rates in 71 countries were compared to per capita food intake rates using age-adjusted cancer rates (year 2000) from the International Agency for Research on Cancer, and food consumption data (1990-1992) provided by the Food and Agricultural Organization of the United Nations. Simple regression models were applied to prostate cancer mortality rates and consumption rates for 38 foods (or food categories), and sunlight levels (latitude from the equator and ultraviolet indexes). The analysis found a correlation between increased prostate cancer mortality rates and the consumption of total animal calories, total animal fat calories, meat, animal fat, milk, sugar, alcoholic beverages, and stimulants. The consumption of cereal grains and rice, in particular, correlated strongly with decreasing prostate cancer mortality. The analysis found that increased sunlight levels and consumption of oilseeds, soybeans, and onions also correlate with decreased prostate cancer mortality risk. Stepwise multiple regression analysis was used to build a regression model with minimum colinearity between the variables. Cereals, total animal fat calories, sugar, and onions are the foods that resulted in a model with the best fit. Cereals, ultraviolet index, sugar, and onions were the variables found to provide the best fit in a model when ambient sunlight exposure was included as a factor.

A multilevel analysis of socioeconomic status and prostate cancer risk

PURPOSE

We investigated whether prostate cancer was associated with socioeconomic status (SES) at the individual level, area level, or a combination of both levels.

METHODS

This population-based case-control study of prostate cancer in men aged 65 to 79 years was conducted between 2000 and 2002 in South Carolina. Complete interviews were available for 407 incident prostate cancer cases and 393 controls (with respective response rates of 61% and 64%). We used educational level to measure individual-level SES and a composite variable capturing income and education from 2000 Census data to measure area-level SES.

RESULTS

After adjustment for race, age, geographic region, and prostate-specific antigen testing, men with some college were at reduced risk for prostate cancer (odds ratio [OR], 0.44; 95% confidence interval [CI], 0.27-0.72), as were men in the highest quartile of area-level SES (OR, 0.52; 95% CI, 0.34-0.80). When assessing individual-level and area-level SES simultaneously and accounting for their nonindependence, the independent negative associations persisted and appeared to be more striking for men with a diagnosis of localized disease, rather than advanced disease.

CONCLUSION

The independent effects of area-level and individual-level SES on prostate cancer risk seen in our study may help explain the conflicting results of previous studies conducted at both levels.

Physical Activity and the Risk of Prostate Cancer in The Netherlands Cohort Study, Results after 9.3 Years of Follow-up

BACKGROUND

The aim of the current study was to evaluate the relation between physical activity and prostate cancer risk with specific emphasis on interaction with body mass index (BMI) and baseline energy intake.

METHODS

The association between prostate cancer and physical activity was evaluated in the Netherlands Cohort Study, conducted among 58,279 men ages 55 to 69 years at entry. Information regarding baseline nonoccupational physical activity, history of sports participation, and occupational physical activity was collected with a questionnaire in 1986. After 9.3 years, 1,386 incident prostate cancer cases were available for case-cohort analyses. Multivariate incidence rate ratios (RR) and corresponding 95% confidence intervals (95% CI) were calculated using Cox regression analyses.

RESULTS

Neither baseline nonoccupational physical activity (RR, 1.01; 95% CI, 0.81-1.25 for >90 versus <30 minutes per day), history of sports participation (RR, 1.04; 95% CI, 0.90-1.22 for ever versus never participated), nor occupational physical activity (RR, 0.91; 95% CI, 0.70-1.18 for >12 versus <8 KJ/min energy expenditure in the longest held job) showed an inverse relation with prostate cancer risk. We found an increased risk of prostate cancer for men who were physically active for >1 hour per day in obese men (BMI > 30) and men with a high baseline energy intake.

DISCUSSION

The results of this current study do not support the hypothesis that physical activity protects against prostate cancer in men.

Alcohol drinking and risk of localized versus advanced and sporadic versus familial prostate cancer in Sweden

BACKGROUND

It is unknown whether the association of alcohol consumption with prostate cancer risk varies between localized and advanced cases, or between sporadic and familial cases.

METHODS

We assessed recent alcohol drinking in a population-based case--control study of Swedish men, including 1499 cases and 1130 controls. Drinking status and average volume, frequency, and type of alcohol consumed were evaluated. Unconditional logistic regression was performed to estimate the odds ratios (ORs) and corresponding 95% confidence intervals (CIs) for associations between alcohol consumption and prostate cancer risk.

RESULTS

Prostate cancer cases were more likely than controls to be current or former, rather than never, drinkers. However, there was no association between recent total alcohol, beer, wine, and liquor consumption and risk of overall prostate cancer, nor advanced, sporadic, or familial prostate cancer. The OR for risk of overall disease among men who drank more than 135 g of total alcohol per week versus non-drinkers was 1.2 (95% CI: 0.9, 1.5), p(trend)=0.12. There was a marginal positive association between alcohol intake and risk of localized disease.

CONCLUSIONS

We detected no association between recent alcohol consumption and risk of advanced, sporadic, or familial prostate cancer, and a borderline positive association with localized disease.

Lifestyle and prostate cancer among older African-American and Caucasian men in South Carolina

OBJECTIVE

We investigated the association between lifestyle and prostate cancer risk among Caucasian and African-American men, separately.

METHODS

This population-based case-control study of prostate cancer among men aged 65-79 years was conducted between 2000 and 2002 in South Carolina. Telephone interviews were completed with 416 incident prostate cancer cases ascertained through the South Carolina Central Cancer Registry, and 429 controls identified through the Health Care Financing Administration Medicare beneficiary file (with respective response rates of 71% and 64%).

RESULTS

Caucasian men working in production, transportation, and material moving had increased prostate cancer risk (odds ratio [OR] = 2.04, 95% confidence interval [CI] 1.17-3.54), while African-American men in the military had reduced prostate cancer risk (OR = 0.19, 95% CI 0.05-0.76). Having five or more prostate specific antigen (PSA) tests within the past five years was associated with prostate cancer among Caucasian men; however, African-American men with prostate cancer tended to have fewer PSA tests. Increasing lycopene consumption was associated with a reduced risk of prostate cancer among Caucasian men (p = 0.03), but not among African-American men.

CONCLUSIONS

In this population-based case-control study conducted in South Carolina we did not find marked differences in lifestyle factors associated with prostate cancer by race.

A Prospective Study of Occupation and Prostate Cancer Risk

A wide variety of occupations has been associated with prostate cancer in previous retrospective studies. Most attention has been paid to farming, metal working, and the rubber industry. Today, these results cannot be affirmed with confidence, because many associations could be influenced by recall bias, have been inconsistent, or have not been confirmed satisfactory in subsequent studies. This study was conducted to investigate and confirm these important associations in a large prospective cohort study. The authors conducted a prospective cohort study among 58,279 men. In September 1986, the cohort members (55-69 years) completed a self-administered questionnaire on potential cancer risk factors, including job history. Related job codes were clustered in professional groups. These predefined clusters were investigated in 3 time windows: 1) profession ever performed, 2) longest profession ever held, and 3) last profession held at baseline. Follow up for incident prostate cancer was established by linkage to cancer registries until December 1993. A case-cohort approach was used based on 830 cases and 1525 subcohort members. To minimize false-positive results, 99% confidence intervals (99% CI) were calculated. Although moderately decreased prostate cancer risks were found for electricians, farmers, firefighters, woodworkers, textile workers, butchers, salesmen, teachers, and clerical workers, none of the relative risks (RR) were found to be statistically significant. For road transporters, metal workers, and managers, no association with prostate cancer risk was found. Although the RR for railway workers, mechanics, welders, chemists, painters, and cooks was moderately increased, these estimates were not statistically significant. For men who reported to have ever worked in the rubber industry, we found a substantially increased prostate cancer risk, but not statistically significant (RR, 4.18; 99% CI = 0.22-80.45). For policemen, we found a substantial and marginally statistically significant increased prostate cancer risk, especially for those who reported working as a policeman for most of their occupational life (RR, 3.91; 99% CI = 1.14-13.42) or as the last profession held at baseline (RR, 4.00; 99% CI = 1.19-13.37). Most of the previously investigated associations between occupation and prostate cancer risk could not be confirmed with confidence in this prospective study. The lack of statistical significance for rubber workers could be caused by the scarcity of rubber workers in this cohort and subsequent lack of power. The results for policemen were substantial and statistically significant, although a conservative value for significance level was used.

A case-control study of diet and prostate cancer in Japan: possible protective effect of traditional Japanese diet

The age-adjusted incidence of prostate cancer is low in Japan, and it has been suggested that the traditional Japanese diet, which includes many soy products, plays a preventive role against prostate cancer. We performed a case-control study on dietary factors and prostate cancer in order to assess the hypothesis that the traditional Japanese diet reduces the risk of prostate cancer. Four geographical areas (Ibaraki, Fukuoka, Nara, and Hokkaido) of Japan were selected for the survey. Average daily intake of food from 5 years before the diagnosis was measured by means of a semi-quantitative food frequency questionnaire. We studied 140 cases and 140 individually age ( +/- 5 years)-matched hospital controls for analysis. Estimates of age-adjusted odds ratios (ORs) and linear trends were calculated by conditional logistic regression models with adjustment for cigarette smoking and total energy intake as confounding factors. Consumption of fish, all soybean products, tofu (bean curds), and natto (fermented soybeans) was associated with decreased risk. ORs of the fourth vs. first quartile and 95% confidence intervals (95%CIs) were 0.45 (0.20-1.02) for fish, 0.53 (0.24-1.14) for all soybean products, 0.47 (0.20-1.08) for tofu, and 0.25 (0.05-1.24) for natto. Consumption of fish and natto showed significantly decreasing linear trends for risk (P < 0.05). Consumption of meat was significantly associated with increased risk (the OR of the second vs. first quartile was 2.19, 95%CI 1.00-4.81). Consumption of milk, fruits, all vegetables, green-yellow vegetables, and tomatoes showed no association. Our results provide support to the hypothesis that the traditional Japanese diet, which is rich in soybean products and fish, might be protective against prostate cancer.

Human prostate cancer risk factors

Prostate cancer has the highest prevalence of any nonskin cancer in the human body, with similar likelihood of neoplastic foci found within the prostates of men around the world regardless of diet, occupation, lifestyle, or other factors. Essentially all men with circulating androgens will develop microscopic prostate cancer if they live long enough. This review is a contemporary and comprehensive, literature-based analysis of the putative risk factors for human prostate cancer, and the results were presented at a multidisciplinary consensus conference held in Crystal City, Virginia, in the fall of 2002. The objectives were to evaluate known environmental factors and mechanisms of prostatic carcinogenesis and to identify existing data gaps and future research needs. The review is divided into four sections, including 1) epidemiology (endogenous factors [family history, hormones, race, aging and oxidative stress] and exogenous factors [diet, environmental agents, occupation and other factors, including lifestyle factors]); 2) animal and cell culture models for prediction of human risk (rodent models, transgenic models, mouse reconstitution models, severe combined immunodeficiency syndrome mouse models, canine models, xenograft models, and cell culture models); 3) biomarkers in prostate cancer, most of which have been tested only as predictive factors for patient outcome after treatment rather than as risk factors; and 4) genotoxic and nongenotoxic mechanisms of carcinogenesis. The authors conclude that most of the data regarding risk relies, of necessity, on epidemiologic studies, but animal and cell culture models offer promise in confirming some important findings. The current understanding of biomarkers of disease and risk factors is limited. An understanding of the risk factors for prostate cancer has practical importance for public health research and policy, genetic and nutritional education and chemoprevention, and prevention strategies.

Exercise and Prostate Cancer

Prostate cancer is a leading cause of cancer morbidity and mortality in men. In addition to improved treatments, strategies to reduce disease risk are urgently required. This review summarises the literature that examines the association between exercise and prostate cancer risk. Between 1989 and 2001, 13 cohort studies were conducted in the US and internationally. Of these, nine showed an association between exercise and decreased prostate cancer risk. Five of 11 case-control studies conducted between 1988 and 2002 reported an association between decreased risk of prostate cancer and high activity levels. Considering all studies performed between 1976 and 2002, 16 out of 27 studies reported reduced risk in men who were most active; in nine out of 16 studies the reduction in risk was statistically significant. Average risk reduction ranged from 10-30%. In aggregate, this evidence suggests a probable link between increased physical exercise and decreased prostate cancer risk. The ability of exercise to modulate hormone levels, prevent obesity, enhance immune function and reduce oxidative stress have all been postulated as mechanisms that may underlie the protective effect of exercise. Exercise may also be of benefit in men undergoing treatment for prostate cancer. Overall, study design and control of potential confounding factors varied greatly among studies, possibly contributing to the variation in results. Epidemiological studies that are better controlled, larger in scale and more carefully designed may help to more fully clarify the relationship between exercise and prostate cancer. In addition, intervention trials that test whether exercise programmes can reduce prostate cancer risk are currently underway to rigorously test the ability of exercise to reduce prostate cancer incidence.

Case-control study of anthropometric measures and prostate cancer risk

A population-based case-control study of 988 stage T2 or greater prostate cancer cases and 1063 controls was conducted in Alberta from November 1997 to December 2000 to examine the influence of anthropometric risk factors on the risk of prostate cancer using several different measures. An in-person interview was conducted, and all anthropometric measurements were taken using standardized methods. Respondents also recalled their body weight at each decade from age 20 to the referent year. Several anthropometric variables were derived, and unconditional logistic regression analyses were performed. The multivariable odds ratios, when comparing the highest to the lowest quartile were: for body mass index, OR = 1.12 (95% CI 0.85-1.47); for waist-hip ratio, OR = 1.07 (0.83-1.38); for height, OR = 0.78 (0.60-1.02); for weight, OR = 0.91 (0.70-1.18); for weight gain since age 20, OR = 0.91 (0.70-1.19); and for difference between minimum and maximum adult weight, OR = 0.89 (0.69-1.16). Our study provides evidence for no association between any measures of anthropometry including several derived measures of changes in weight over lifetime and prostate cancer risk.

Lifestyle issues and genitourinary tumours

A variety of lifestyle factors, including physical activity, artificial sweeteners, alcohol consumption and smoking, have been reported to contribute to the risk of developing urological malignancies. A great number of epidemiological studies suggest that sports and physical activity may have a preventive influence on genitourinary tumours, especially on the incidence of prostate cancer. Smoking appears to be the most relevant lifestyle factor significantly increasing both incidence and mortality from bladder cancer. Furthermore, there is evidence implicating an association between tobacco use and kidney cancer. In contrast, prostate and testicular cancers are unlikely to be linked to tobacco use. As far as alcohol is concerned, most studies indicate that neither amount nor type of alcohol seems to be clearly associated with a risk of developing urological malignancies. However, some more recent cohort studies suggest a moderately increased risk for prostate and bladder cancer for specific types of alcohol. On the other hand, there is evidence that moderate alcohol consumption may even protect women from developing renal cancer. Since the introduction of artificial sweeteners, reports of potential cancer risks have circulated periodically through the mass media. The wide distribution of these agents and the fact that mostly combinations of the different compounds are added to a broad variety of food, drinks, drugs, and hygiene products complicates a systematic analysis of their potential impact on the development of urological malignancies. Nevertheless, so far not a single study has convincingly demonstrated a statistically significant risk of bladder cancer due to the consumption of artificial sweeteners. This survey demonstrates that the individual assessment of lifestyle factors not only may identify groups with an increased risk for urological malignancies but also clearly displays a potential for tumour prevention.

Physical activity and cancer prevention: etiologic evidence and biological mechanisms

Scientific evidence is accumulating on physical activity as a means for the primary prevention of cancer. Nearly 170 observational epidemiologic studies of physical activity and cancer risk at a number of specific cancer sites have been conducted. The evidence for decreased risk with increased physical activity is classified as convincing for breast and colon cancers, probable for prostate cancer, possible for lung and endometrial cancers and insufficient for cancers at all other sites. Despite the large number of studies conducted on physical activity and cancer, most have been hampered by incomplete assessment of physical activity and a lack of full examination of effect modification and confounding. Several plausible hypothesized biological mechanisms exist for the association between physical activity and cancer, including changes in endogenous sexual and metabolic hormone levels and growth factors, decreased obesity and central adiposity and possibly changes in immune function. Weight control may play a particularly important role because links between excess weight and increased cancer risk have been established for several sites, and central adiposity has been particularly implicated in promoting metabolic conditions amenable to carcinogenesis. Based on existing evidence, some public health organizations have issued physical activity guidelines for cancer prevention, generally recommending at least 30 min of moderate-to-vigorous intensity physical activity on > or =5 d/wk. Although most research has focused on the efficacy of physical activity in cancer prevention, evidence is increasing that exercise also influences other aspects of the cancer experience, including cancer detection, coping, rehabilitation and survival after diagnosis.

Does amount or type of alcohol influence the risk of prostate cancer?

BACKGROUND

Prostate cancer is one of the most common cancers among men, and it is unknown whether alcohol is associated with the development of prostate cancer.

METHODS

The relationship between amount or type of alcohol and prostate cancer was studied in a pooled prospective setting conducted from 1976 to 1994 in Copenhagen, Denmark. The study population consisted of 12,989 subjects drawn from three different cohorts. During a mean follow-up of 12.3 yr, 233 subjects developed prostate cancer.

RESULTS

None of the estimates for consumed amount of total alcohol diverged significantly from unity. Furthermore, drinkers of more than 13 beers, 13 glasses of wine, and 13 drinks of spirits had a risk of 1.03 (CI: 0.67, 1.60), 0.92 (CI: 0.42, 1.99), and 1.01 (CI: 0.52, 1.98), respectively, compared with abstainers of the given beverage of alcohol.

CONCLUSION

These results suggest that neither amount nor type of alcohol is associated with the risk of prostate cancer.

Is obesity a risk factor for prostate cancer, and does it even matter? A hypothesis and different perspective

Measurement of obesity is not as simple as its definition. Currently, several methods of measuring obesity are used in clinical studies. Skinfold thickness, crude weight, lean body mass (LBM), body mass index (BMI), and waist-to-hip ratio (WHR) are some of the more popular methods, but each contains its inherent strengths and flaws. In general, the results of the largest studies on prostate cancer and obesity have not been conclusive. One of the largest studies found an inverse relation to prostate cancer in the youngest age groups. The age and duration of obesity or any rapid changes in weight gain, along with other unhealthy exposures, may have some relation to prostate cancer incidence and mortality. Early intrinsic or extrinsic exposure to estrogen or estrogenlike compounds may provide a protective effect. The timing and duration of a higher estrogen and/or lower testosterone exposure may have a beneficial or detrimental impact on the prognosis of an established prostate tumor. Negative exposures over time such as low levels of sex hormone-binding globulin (SHBG), a greater exposure to growth factors, elevated insulin levels, greater sympathetic activity, higher cholesterol levels, immune system dysfunction, inadequate diets, smoking status, and other factors may be associated with an increased risk of prostate cancer and other diseases. Obesity may also be associated with other cancers for similar and different reasons. For example, morbidity and mortality from postmenopausal breast cancer, colon, kidney, and other cancers are potentially associated with obesity. Other comorbidities such as cataracts, coronary heart disease, diabetes, erectile dysfunction, hypertension, and others are also associated with obesity. The 2 largest prospective studies on BMI and overall mortality have also demonstrated the substantial negative impact of excess weight on society. Prostate cancer risk and obesity need further research to establish if a true association exists, but at this time, does it really matter? Overall, the profound adverse effect of being obese on general health is dramatic, and this is what clinicians and patients need to remember.

Hospitalization for prostate cancer among the older men in the longitudinal study on aging, 1984-1991

BACKGROUND

Factors associated with being hospitalized with indications of prostate cancer were examined. A secondary analysis of the older men in the Longitudinal Study on Aging (LSOA) used baseline (1984) interview data and Medicare hospital claims for 1984 through 1991.

METHODS

The analytic sample consisted of 2254 men who were 70 to 95 years old (mean 75.8 years) at baseline and who were self-respondents to the LSOA. Case-identification involved primary prostate cancer (ICD9-CM code 185) and personal history of prostate cancer (ICD9-CM code V10.46) hospital discharge diagnoses. Multivariable logistic regression techniques were used.

RESULTS

There were 154 cases (6.8%) of prostate cancer, including 109 identified by active diagnostic codes only, 15 identified by personal history codes only, and 30 identified by both. No associations with age, race, or ethnicity were observed. Being hospitalized with indications of prostate cancer was more likely in the presence of a history of cancer at any site, urinary control problems, greater body mass, maximum social interaction, or living in core Standard Metropolitan Statistical Area counties. Men who regularly attended religious services, had not seen a physician for 2 years, and did not feel in control of their health were less likely to have been hospitalized with indications of prostate cancer.

CONCLUSIONS

These data suggest that the traditional associations between prostate cancer and age, race, and ethnicity do not apply to being hospitalized with indications of the disease among older men. However, body mass, history and symptoms, personal beliefs, access, and geographic practice patterns are associated with being hospitalized with indications of prostate cancer.

Alcohol consumption and risk of prostate cancer: The Harvard Alumni Health Study

BACKGROUND

Although many studies suggest that consumption of alcohol increases the risk of several site-specific cancers, the evidence remains unclear for prostate cancer. Few data exist on beverage-specific associations as well as lifetime patterns of alcohol consumption and prostate cancer risk.

METHODS

We prospectively followed 7612 Harvard alumni (mean age 66.6 years) from 1988 through 1993, during which 366 cases of incident prostate cancer occurred. Self-reported alcohol consumption was assessed at baseline from wine, beer, and liquor intake. Previous assessments during college and in 1977 were also available.

RESULTS

Overall, the mean total alcohol consumption in 1988 was 123.1 g/week, of which 28.6% was from wine, 15.8% from beer, and 55.6% from liquor. Compared to men reporting almost never drinking alcohol in 1988, the multivariate relative risks (95% CI) for 1 drink/month to < 3 drinks/week, 3 drinks/week to < 1 drink/ day, 1 to < 3 drinks/day, and > or = 3 drinks/day were 1.33 (0.88-2.01), 1.65 (1.12-2.44), 1.85 (1.29-2.64), and 1.33 (0.86-2.05), respectively. Wine or beer consumption was unassociated with prostate cancer; however, moderate liquor consumption was associated with a significant 61-67% increased risk of prostate cancer (P, non-linear trend < 0.001). Men initiating alcohol consumption between 1977 and 1988 had a twofold increased risk of prostate cancer compared to men with almost no alcohol consumption at both times.

CONCLUSIONS

In contrast to the majority of previous studies, we found a positive association between moderate alcohol consumption and the risk of prostate cancer. Liquor, but not wine or beer, consumption was positively associated with prostate cancer.

Physical activity and cancer risk: dose-response and cancer, all sites and site-specific

PURPOSE

The association between physical activity and overall and site-specific cancer risk is elaborated in relation to whether any observed dose-response association between physical activity and cancer can be interpreted in terms of how much physical activity (type, intensity, duration, frequency) is needed to influence site- and gender-specific cancer risk.

METHODS

Observational studies were reviewed that have examined the independent effect of the volume of occupational physical activity (OPA) and/or leisure time physical activity (LPA) on overall and site-specific cancer risk.

RESULTS

The evidence of cohort and case-control studies suggests that both leisure time and occupational physical activity protect against overall cancer risk, with a graded dose-response association suggested in both sexes. Confounding effects such as diet, body weight, and parity are often included as a covariate in the analyses, with little influence on the observed associations. A crude graded inverse dose-response association was observed between physical activity and colon cancer in 48 studies including 40,674 colon/colorectal cancer cases for both sexes. A dose-response effect of physical activity on colon cancer risk was especially observed, when participation in activities of at least moderate activity (>4.5 MET) and demonstrated by activities expressed as MET-hours per week. An observed inverse association with a dose-response relationship between physical activity and breast cancer was also identified in the majority of the 41 studies including 108,031 breast cancer cases. The dose-response relationship was in particular observed in case-control studies and supported by observations in cohort studies when participation in activities of at least moderate activity (>4.5 MET) and demonstrated by activities expressed by MET-hours per week. This association between physical activity and breast cancer risk is possibly dependent on age at exposure, age at diagnosis, menopausal status and other effect modifiers, e.g., body mass index. Furthermore, data concerning carcinoma of other cancers (prostate, lung, endometrium, ovary, and testicular cancers) are required.

CONCLUSION

A protective effect of physical activity on site-specific cancer risk with a dose-response association between physical activity and colon and pre- and postmenopausal breast cancer supported by identified biological mechanisms has been observed. The optimal permutation of type, intensity, duration, and frequency of physical activity across the lifespan is unclear, but it is gender, age, and site specific and supports moderate activity (>4.5 MET) more than light activities (<4.5 MET). The complicated nature of the physical activity variable, combined with lack of knowledge regarding possible biological mechanisms operating between physical activity and cancer, warrants further studies including controlled clinical randomized trials.

Changing relationship between socioeconomic status and prostate cancer incidence

BACKGROUND

Understanding the relationship between socioeconomic status (SES) and prostate cancer incidence could identify populations that should be targeted for intervention and prevention programs. We examined this relationship within the major racial/ethnic groups during the period 1972 through 1997, which spans the introduction of prostate-specific antigen (PSA) testing.

METHODS

We used data from the population-based Los Angeles Cancer Surveillance Program to examine age-adjusted prostate cancer incidence rates in five SES groups over three specific calendar periods by racial/ethnic subpopulation (white, black, Asian, and Hispanic) and by stage of disease at diagnosis. Linear regression analysis was used to test for trends in the age-adjusted incidence rates that were associated with increasing levels of SES. All P values were two-sided.

RESULTS

For men diagnosed with prostate cancer before 1987, when the test for PSA was not widely available, we found no association between SES and the incidence of prostate cancer in any of four racial/ethnic subpopulations or between SES and the stage of disease at diagnosis. In contrast, among men who were diagnosed with prostate cancer after 1987, SES was statistically significantly and positively associated with prostate cancer incidence in men from all racial/ethnic subpopulations except Asians (P =.01 for white men, P =.001 for black men, P =.02 for Hispanic men, P =.06 for Asian men, and P =.01 for all men combined). Higher SES was statistically significantly associated with cancers of earlier stage (P =.01 for localized cancer and P =.00 for regional cancer) for men who were diagnosed with prostate cancer after 1987.

CONCLUSIONS

The association between SES and prostate cancer incidence after 1987 may reflect more prevalent PSA screening in populations with higher SES due to their greater access to health care. SES should, therefore, be considered an important factor in interpreting variations and time trends in prostate cancer incidence.

Impact of socioeconomic status and race on clinical parameters of patients undergoing radical prostatectomy in an equal access health care system

OBJECTIVES

To analyze the relationships among socioeconomic status (SES), race, and the clinical parameters of patients undergoing radical prostatectomy (RP) in an equal access health care system.

METHODS

The Department of Defense Center for Prostate Disease Research longitudinal prostate cancer database from multiple military institutions was used to analyze the clinical, pathologic, and outcome data of 1058 patients with localized (Stage T2c or lower) prostate cancer and a preoperative prostate-specific antigen (PSA) level of 20 ng/mL or less who underwent RP between January 1987 and December 1997. Military rank (officer versus enlisted) was used as a surrogate measure of SES.

RESULTS

The percentage of patients with pathologic Gleason grade 7 or greater prostate cancer was higher in enlisted (45%) than in officer (37%) patients (P = 0. 021). However, no difference was found between these groups with respect to pathologic stage or biochemical recurrence rates. African Americans presented at a younger age (P = 0.003), with a higher pretreatment PSA level (P = 0.001), and demonstrated higher biochemical recurrence rates than other ethnic groups (P = 0.037). The Cox proportional hazards analysis showed that a lower SES (P = 0.010) but not African American race (P = 0.696) was an independent predictor of a higher grade (Gleason grade 7 or higher) cancer. However, biochemical progression was more common in African American men (P = 0.035) and was not related to SES (P = 0.883).

CONCLUSIONS

In an equal access health care system, patients of lower SES presented with higher grade prostate cancer at the time of RP. However, only African American race predicted biochemical progression after RP.

Socio-economic and lifestyle factors associated with the risk of prostate cancer

International and interethnic differences in prostate cancer incidence suggest an environmental aetiology, and lifestyle and socio-economic factors have been studied, but with divergent results. Information on a cohort of 22,895 Norwegian men aged 40 years and more was obtained from a health examination and two self-administered questionnaires. Information on incident cases of prostate cancer was made available from the Cancer Registry. We used the Cox proportional hazards model to calculate incidence rate ratios as estimates of the relative risk (RR) with 95% confidence interval (CI). Reported P-values are two-sided. During a mean follow-up of 9.3 years, 644 cases were diagnosed. Risk was elevated among men in occupations of high compared to low socio-economic status (RR = 1.30; 95% CI 1.05-1.61), and among men with high education compared to the least educated (RR = 1.56; 95% CI 1.11-2.19). A RR of 1.56 (95% CI 0.97-2.44) suggests a higher risk among divorced or separated men, compared with married men. We also found indications of a weak negative association with leisure-time physical activity (RR = 0.80; 95% CI 0.62-1.03 for high vs low activity), a weak positive association with increasing number of cigarettes (P = 0.046), while alcohol consumption was not related to the risk of prostate cancer. These results show that high socio-economic status is associated with increased risk of prostate cancer, and that divorced or separated men might be at higher risk than married men. Data from this study also indicate that high levels of physical activity may reduce prostate cancer risk.

A prospective study of physical activity and risk of prostate cancer in US physicians

BACKGROUND

Exercise can suppress androgen production and may thus decrease the risk of prostate cancer. However, findings from epidemiological studies assessing physical activity and risk of prostate cancer are inconsistent.

METHODS

We prospectively examined the association between physical activity and prostate cancer risk in the Physicians' Health Study (PHS), a randomized trial of low-dose aspirin and beta-carotene among 22,071 men aged 40-84 without self-reported myocardial infarction, stroke and cancer. At baseline in 1982, men were asked about the frequency of exercise vigorous enough to work up a sweat. Physical activity was assessed in a similar fashion again at 36 months of follow-up.

RESULTS

During 11.1 years of follow-up (258 779 person-years), 982 cases of prostate cancer occurred and were confirmed by medical record review. After adjustment for potential confounding factors (including age, height, randomized treatment assignment, smoking status, alcohol intake, use of multivitamins, history of diabetes, history of hypertension and history of high cholesterol), the relative risks for prostate cancer associated with exercise vigorous enough to work up a sweat were 1.0 (referent) for frequency less than once per week, 1.02 (95% CI: 0.82-1.26) for once per week, 1.07 (95% CI: 0.90-1.27) for 2-4 times per week, and 1.11 (95% CI: 0.90-1.36) for 5+ times per week. Across all subgroups of men categorized by age, body mass index, smoking status, alcohol intake, use of multivitamins, history of diabetes, history of hypertension and history of high cholesterol, there were no significant associations between frequency of exercise vigorous enough to work up a sweat and prostate cancer risk. After excluding cases of prostate cancer that occurred during the first 36 months of follow-up, again, there was no significant association. Combining physical activity assessments at baseline and at 36 months also yielded no significant association with prostate cancer risk.

CONCLUSIONS

These observational data from the Physicians' Health Study do not support the hypothesis that increased physical activity reduces the risk of prostate cancer.

Meta-analysis for combining relative risks of alcohol consumption and prostate cancer

BACKGROUND

Prostate cancer has become the most common cancer among men in the United States, but little is known about factors associated with prostate cancer incidence.

METHODS

A meta-analysis of studies published prior to July 1998 was conducted to pool relative risk (RR) estimates from the existing literature on the association between prostate cancer and alcohol consumption, in an attempt to determine whether there is an association, and if so, what its magnitude is.

RESULTS

The overall pooled RR estimate was 1. 05 for both fixed and random effects models, based on six cohort studies and 27 case-control studies. The RR estimate varied little by study design. Among types of consumption, the highest risk was found for beer (RR = 1.27), but this was based on only eight studies that reported type of alcohol consumed. A linear dose-response was fit to the 15 studies reporting amount of alcohol consumed, finding a RR of 1.05 (95% confidence interval (CI), 0.91-1.20) for each additional drink of alcohol per day or a RR of 1.21 for 4 drinks per day. When the average drinks per day consumed in the 15 studies were used to estimate the overall risk for all 33 studies, a RR of 1.02 was found for each additional drink of alcohol per day.

CONCLUSIONS

Overall, no association between prostate cancer and alcohol consumption was seen. While some categories of consumption showed an increased risk, the studies reporting such categories appeared to be biased towards reporting a positive association among the categories.

Alcohol and prostate cancer in the NHANES I epidemiologic follow-up study. First National Health and Nutrition Examination Survey of the United States

PURPOSE

We prospectively investigated the association between alcohol consumption and prostate cancer in the Epidemiologic Follow-up Study (NHEFS) of the first National Health and Nutrition Examination Survey (NHANES I).

METHODS

There were two cohorts: 1) Cohort I, followed from baseline (1971-75) through 1992, included 5766 men ages 25-74 years (median follow-up = 17 years); and 2) Cohort II, followed from the first follow-up round for Cohort I (1982-84) through 1992, included the 3868 men in Cohort I free of prostate cancer in 1982-84 (median follow-up = 9 years). Alcohol consumption was assessed at baseline as usual consumption, and at follow-up as usual consumption and as distant past consumption at the ages of 25, 35, 45, and 55.

RESULTS

There were 252 incident cases of prostate cancer. Consistent with most previous studies, we found no significant associations between usual total alcohol consumption and prostate cancer in Cohorts I or II [p = non significant (NS)], except for a significant inverse association at the heaviest level of drinking in Cohort II [relative risk (RR) = 0.23, 95% confidence interval (CI) = 0.06-0.95]. Further study of heavy drinkers in Cohort II revealed significant inverse associations between distant past heavy drinking (defined as > 25 drinks/week) and prostate cancer at age 25 (RR = 0.20, 95% CI = 0.06-0.63), age 35 (RR = 0.30, 95% CI = 0.12-0.77), and age 45 (RR = 0.39, 95% CI = 0.17-0.93), but not at age 55 (RR = 0.43, 95% CI = 0.17-1.10).

CONCLUSIONS

These results suggest that it may be important to consider distant past alcohol consumption in etiologic studies of prostate cancer. However, our results were based on small numbers of cases who were heavy drinkers and require replication.

Alcohol and other beverage use and prostate cancer risk among Canadian men

There are very few large scale studies that have examined the association of prostate cancer with alcohol and other beverages. This relationship was examined in a case-control study conducted in 3 geographical areas of Canada [Metropolitan Toronto (Ontario), Montreal (Quebec), and Vancouver (British Columbia)] with 617 incident cases and 637 population controls. Complete history of beverage intake was assessed by a personal interview with reference to a 1-year period prior to diagnosis or interview. In age- and energy-adjusted models for all centers combined, the odds ratio (OR) for the highest quintile of total alcohol intake was 0.89. For alcoholic beverages separately, it was 0.68 for the highest tertile of beer, 1.12 for wine and 0.86 for liquor. The decreasing trend was significant for beer intake. The results were only significant for British Columbia out of all the 3 centers studied. Whereas coffee and cola intake was not associated with prostate cancer, a decrease in risk was observed with tea intake of more than 500 g per day (OR 0.70). Our results do not support a positive association between total alcohol, coffee and prostate cancer.

Alcohol use and prostate cancer in U.S. whites: no association in a confirmatory study

BACKGROUND

In a recent study among U.S. men with prostate cancer, alcohol consumption was associated with an increase in prostate cancer risk. This finding could have considerable public health implications. We therefore set out to confirm the reported association in a study of comparable scale, using the same alcohol exposure categories.

METHODS

The association was evaluated in a case-control study of 699 white prostate cancer cases and 2,041 matched controls, admitted between 1977-1991 to 20 U.S. hospitals.

RESULTS

No association was seen between prostate cancer and alcohol intake comparing ever, current, and former to never drinkers, not even for the highest reported level of alcohol consumption.

CONCLUSIONS

Our failure to confirm the reported association agrees with the findings of most studies that, within a wide range of alcohol intake, there is no relation between alcohol consumption and prostate cancer. However, some studies suggest that alcoholics may have an increased prostate cancer risk. This needs further exploration.

Diet, nutrition, and prostate cancer

Cancer of the prostate gland is one of the most common malignancies in affluent nations, in part due to the application of new screening and diagnostic tools. The development of life-threatening prostate cancer is the culmination of a complex series of initiation and promotional events over a period of decades and under the influence of many interacting genetic and environmental factors. A rapidly accumulating scientific literature provides compelling evidence for the hypothesis that diet and nutrition are important factors modifying risk of prostate cancer. Additional resources devoted to interactive research efforts by laboratory scientists and epidemiologists will provide further enlightenment and continued refinement of our assessment of risks and benefits for specific nutrients and dietary patterns. These studies provide hope that evidence-based dietary interventions will significantly impact the risk of prostate cancer and enhance the efficacy of therapeutic interventions.

Physical activity and the primary prevention of cancer

Evidence has been accumulating that suggests that physical activity may help reduce the risk of cancer. Physically active people have been shown to have a decreased rate of all-cancer mortality. The incidence of colon, breast, and perhaps prostate cancer are decreased in more active people when compared with their sedentary peers. Chronic physical activity may decrease tumor risk by its effect on natural immunity, antioxidant defenses, improved energy balance, hormonal changes, or by other unknown mechanisms.

Review of epidemiologic studies of alcohol and prostate cancer: 1971-1996

Prostate cancer is the most common cancer among American men, with few established risk factors. The association between prostate cancer and alcohol, a potentially modifiable risk factor, has been examined in numerous studies. We systematically reviewed the literature on alcohol and the incidence of prostate cancer by searching for published cohort and case-control studies using computerized databases, references, and experts, by evaluating studies for validity, and by summarizing the results and providing research recommendations. We found compelling evidence for no association between low-to-moderate alcohol consumption and prostate cancer. Most studies, however, did not assess the risk of heavy drinking, where there has been some suggestion of increased risk, or of lifetime patterns of drinking. None of the studies have used genetic markers, nor have they been conducted in populations with known familial risk. Further studies in some populations may be warranted.

Cigarette smoking and prostate cancer: no relation with six measures of lifetime smoking habits in a large case-control study among U.S. whites

BACKGROUND

The study was undertaken to describe the association between lifetime cigarette smoking habits and prostate cancer. Whereas most case-control and cohort studies report no association, the positive findings from some large cohort studies are difficult to ignore. The available information on lifetime smoking habits from most studies is limited however.

METHODS

In a study of 1,097 prostate cancer cases and 3,250 matched controls, admitted between 1969 and 1991 to U.S. hospitals, several ordinal measures of lifetime smoking were compared to look for dose-response or threshold associations.

RESULTS

No association was seen between prostate cancer and former or current smoking, age started smoking, number of years smoked, cigarettes per day smoked, the number of years since quitting, and lifetime tar exposure.

CONCLUSIONS

Our data provide the most complete dose-response smoking information to date, and support the findings from the majority of studies that prostate cancer is not associated with cigarette smoking.

The importance of marital and socioeconomic status in incidence and survival of prostate cancer. An analysis of complete Norwegian birth cohorts

BACKGROUND

Previous studies of the association between social and family status and prostate cancer (PCa) have given somewhat divergent results. Little attention has been paid to the possible importance of these factors for survival.

METHODS

In this study, hazard regression models for PCa incidence and mortality were estimated on the basis of register- and census-based histories for complete Norwegian birth cohorts, giving a follow-up time of 16 million person years and 30,000 cases of PCa.

RESULTS

A significant excess incidence of about 20% was found for ever-married men and for those with higher education. Marriage and socioeconomic resources appeared, however, to have a favorable effect on survival. Five-year relative survival from metastasized cancer among men with a high educational level was found to be 15 percentage points higher than among men with lower education.

CONCLUSIONS

The observed differences in incidence are not easily explained. They apparently run counter to the hypothesis that multiple partners give a higher PCa risk, but may be consistent with the view that fat and meat consumption is risky. Better survival from PCa in higher socioeconomic groups and among married men may reflect differences in the search for, access to, or quality of treatment or a better constitution to fight the disease.

Diet, nutrition and prostate cancer

Although much has been written, little is known about the causes of prostate cancer. Variations between populations in the incidence of invasive cancers, together with changes in the incidence of invasive cancers in migrants, have pointed to environmental (lifestyle) factors that might be amenable to intervention. Conversely, there is a lack of international variation in the prevalence of microscopic tumours, so the essential question is: what causes only some of the common microscopic tumours to become aggressive? Dietary factors hold the most promise in this regard and have been the subject of recent reviews. The strongest and most consistent effects are positive associations with animal products such as red meats, eggs and dairy foods, and possibly by implication, fat. Evidence of a protective effect of fruit and vegetables is weak and inconsistent, as is the relationship with vitamin A and carotenoids, such as beta-carotene. There are some interesting leads. Lycopene, the carotenoid found in tomatoes, has been reported to be protective; alpha-tocopherol supplementation has shown a protective effect in one intervention study; and vitamin D has been shown to be protective in a prospective study. Interest is also growing in phytoestrogens and the extent to which dietary manipulation with these and other phytochemicals might influence prostate cancer by modifying male sex hormone levels or actions. There is limited evidence of associations with obesity. It is not known whether these are related to a particular dietary pattern or to possible physiological effects on the male's hormonal milieu. Associations with lean body mass are likely to be related to the action of androgens during growth and development. Dietary and nutritional effects on prostate cancer do not appear to be strong, but they may be subtle and attenuated by measurement error. To explore these aspects further will require large prospective studies that include improved (repeated) dietary measurements and also blood sampling, so that genetic polymorphisms can be adequately investigated. Such studies are underway.

Prostate cancer, race, and socioeconomic status: inadequate adjustment for social factors in assessing racial differences

BACKGROUND

This paper reviews the state of the art in analyzing race, social factors, and economic factors in cancer research, with an emphasis on prostate cancer and the role of socioeconomic status (SES) in racial differences in mortality. It analyzes the quality of articles in the literature that assess the role of SES in cancer mortality.

METHODS

English-language titles were identified using MEDLINE with publication dates from mid-1985 through July 1994. Articles in the references of these articles were also included in the final selection, based originally on title and ultimately on content, dating back to 1978. Articles that included SES information and distinguished between whites and African-Americans were chosen, resulting in a final selection of 21 articles. Articles are summarized with consideration of five criteria considered minimal requirements of a well-designed study of the role of race in cancer mortality: (1) SES measure(s) should be on an individual level, not census level; (2) SES should be controlled for when making comparisons between whites and blacks; (3) SES should include at least (individual level) measures of income and education; (4) sample sizes are sufficient for the relevant populations; and (5) specific cancer sites should be studied separately.

RESULTS

Of the articles reviewed, only two meet the minimum standards, neither of which studied prostate cancer. It is not clear whether observed racial differences in prostate cancer are directly attributable to race or reflect underlying social factor differences between whites and African-Americans.

CONCLUSIONS

In the future, specific characteristics of SES should be measured at the individual level; there is a need for expansion and standardization of data in terms of social and economic content; other methodological advances are needed in modeling to take into consideration the influence of SES in outcome research related to cancer.