Family aggregation of cancer of the prostate in Quebec: the tip of the iceberg

An epidemiological reappraisal of the familial aggregation of prostate cancer: a meta-analysis

Studies on familial aggregation of cancer may suggest an overall contribution of inherited genes or a shared environment in the development of malignant disease. We performed a meta-analysis on familial clustering of prostate cancer. Out of 74 studies reporting data on familial aggregation of prostate cancer in unselected populations retrieved by a Pubmed search and browsing references, 33 independent studies meeting the inclusion criteria were used in the analysis performed with the random effects model. The pooled rate ratio (RR) for first-degree family history, i.e. affected father or brother, is 2.48 (95% confidence interval: 2.25-2.74). The incidence rate for men who have a brother who got prostate cancer increases 3.14 times (CI:2.37-4.15), and for those with affected father 2.35 times (CI:2.02-2.72). The pooled estimate of RR for two or more affected first-degree family members relative to no history in father and in brother is 4.39 (CI:2.61-7.39). First-degree family history appears to increase the incidence rate of prostate cancer more in men under 65 (RR:2.87, CI:2.21-3.74), than in men aged 65 and older (RR:1.92, CI:1.49-2.47), p for interaction = 0.002. The attributable fraction among those having an affected first-degree relative equals to 59.7% (CI:55.6-63.5%) for men at all ages, 65.2% (CI:57.7-71.4%) for men younger than 65 and 47.9% (CI:37.1-56.8%) for men aged 65 or older. For those with a family history in 2 or more first-degree family members 77.2% (CI:65.4-85.0%) of prostate cancer incidence can be attributed to the familial clustering. Our combined estimates show strong familial clustering and a significant effect-modification by age meaning that familial aggregation was associated with earlier disease onset (before age 65).

Hereditary Predisposition and Prostate Cancer

A genetic component in prostate cancer (PCa) has been recognized for decades, and much evidence has been accumulated in favor of a significant, but heterogeneous hereditary component in PCa.

Purpose

We studied the incidence of the familial and hereditary forms of PCa in our population of patients with a diagnosis of PCa clinically localized and age at diagnosis <65 yrs. Materials and methods: We administered a questionnaire to 667 patients submitted to radical prostatectomy from July 1978 to December 2002, obtaining a complete familial oncological anamnesis in 499 patients. The patients were followed-up until death or until 30 June 2004. Patients were classified into three categories according to Carter: familial, hereditary and sporadic PCa.

Results

A positive family history for PCa was found in 72 patients (14.4%). In 15 patients (3%), we observed a hereditary form of PCa and in 57 patients (11.4%) a familial form. Patients with hereditary PCa had a lower age at diagnosis (55 yrs). Genealogical pedigrees ruled out mendelian dominant autosomical transmission. No difference was found in the preoperatory, clinical and pathological features among the three PCa groups. A statistically significant familial association was found between PCa and cancer of breast and uterus.

Conclusions

This study supports evidence of a hereditary predisposition to PCa and the suggestion that an excess familial risk of PCa is due to the inheritance of multiple moderate-risk genetic variants.

The clinical genetics of prostate cancer

Prostate cancer is the most common cancer in men and the second highest cause of cancer-related mortality in the U.K. A genetic component in predisposition to prostate cancer has been recognized for decades. One of the strongest epidemiological risk factors for prostate cancer is a positive family history. The hunt for the genes that predispose to prostate cancer in families has been the focus of many research groups worldwide for the past 10 years. Both epidemiological and twin studies support a role for genetic predisposition to prostate cancer. Familial cancer loci have been found, but the genes that cause familial prostate cancer remain largely elusive. Unravelling the genetics of prostate cancer is challenging and is likely to involve the analysis of numerous predisposition genes. Current evidence supports the hypothesis that excess familial risk of prostate cancer could be due to the inheritance of multiple moderate-risk genetic variants. Although research on hereditary prostate cancer has improved our knowledge of the genetic aetiology of the disease, a lot of questions still remain unanswered.

This article explores the current evidence that there is a genetic component to the aetiology of prostate cancer and attempts to put into context the diverse findings that have been shown to be possibly associated with the development of hereditary prostate cancer. Linkage searches over the last decade are summarised. It explores issues as to why understanding the genetics of prostate cancer has been so difficult and why despite this, it is still a major focus of research. Finally, current and future management strategies of men with Hereditary Prostate Cancer (HPC) are discussed.

Changing trends of prostate cancer in Asia

Although Asian people have the lowest incidence and mortality rates of prostate cancer in the world, these rates have risen rapidly in the past two decades in most Asian countries. Prostate cancer has become one of the leading male cancers in some Asian countries. In 2000, the age-adjusted incidence was over 10 per 100000 men in Japan, Taiwan, Singapore, Malaysia, the Philippines and Israel. Although some of the increases may result from enhanced detection, much of the increased incidence may be associated with westernization of the lifestyle, with increasing obesity and increased consumption of fat. The differences in incidences between native Americans and Asian immigrants are getting smaller, reflecting a possible improvement of diagnostic efforts and changes of environmental risk factors in Asian immigrants. Nevertheless, the huge variations in incidences among ethnic groups imply that there are important genetic risk factors. The stage distributions of prostate cancer in Asian populations are still unfavorable compared to those of Western developed countries. However, a trend towards diagnosing cancer with more favorable prognosis is seen in most Asian countries. Both genetic and environmental risk factors responsible for elevated risks in Asian people are being identified, which may help to reduce prostate cancer incidence in a chemopreventive setting.

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.

Relative risk of prostate cancer for men with affected relatives: systematic review and meta-analysis

An increased risk of prostate cancer associated with a family history of prostate cancer has been documented in multiple published reports. Risk has been shown to vary by degree of relationship and age of onset of disease in the affected relative. Several studies, using various designs, have estimated the relative risk (RR) for these associations. The purpose of our study was to identify and summarize published reports on the relationship between risk of prostate cancer and family history, which is defined as having a father, brother, any first- or second-degree relative or other relative affected with prostate cancer. A Medline and manual search from 1982 to 2000 identified 24 studies that reported RR and confidence intervals (CI) and satisfied inclusion criteria. Pooled RR estimates based upon a weighted average model were as follows: any affected family member RR = 1.93, CI 1.65-2.26; affected first-degree relative RR = 2.22, CI 2.06-2.40; affected second-degree relative RR = 1.88, CI 1.54-2.30; father with prostate cancer RR = 2.12, CI 1.82-2.51; and brother with prostate cancer RR = 2.87, CI 2.21-3.73). Statistical comparison of pooled data demonstrated that the RR is significantly higher for affected brother than for affected father (p < 0.03). A sensitivity analysis demonstrated that these results are robust with respect to population bias. This meta-analysis confirms that risk of prostate cancer is associated with family history of disease and improves the quantification of this risk.

A systematic review and meta-analysis of familial prostate cancer risk

OBJECTIVE

To identify published studies quantifying familial prostate cancer risks in relatives of prostate cancer cases and, by meta-analysis, obtain more precise estimates of familial risk according to the family history.

METHODS

Thirteen case-control and cohort studies were identified which have reported risks of prostate cancer in relatives of prostate cancer cases. Pooled estimates of risk for various categories of family history were obtained by calculating the weighted average of the log relative risk (RR) estimates from studies.

RESULTS

The pooled RR (95% confidence interval) in first-degree relatives was 2.5 (2.2-2.8). There was evidence that this was highest in relatives of cases diagnosed before age 60 years and that RRs declined with age. The risk for the few men with two affected relatives was increased 3.5-fold (2.6-4.8). RRs to sons of cases appeared to be lower than in brothers; a complete explanation of this observation is uncertain.

CONCLUSION

Men with a family history of prostate cancer have a significantly greater risk of developing prostate cancer than those with no such history. Risks are greatest for relatives of cases diagnosed when young and those with more than one relative affected.

Familial prostate and breast cancer in men treated with prostatectomy for prostate cancer: a population based case-control study

PURPOSE

We assessed familial prostate and breast cancer in Quebec.

MATERIALS AND METHODS

Using a self-administered mail survey we assessed the prevalence of prostate and breast cancer in first degree relatives of 1,633 men treated with prostatectomy for prostate cancer in the province of Quebec and in first degree relatives of 1,386 spouse controls.

RESULTS

The OR of familial breast cancer was 1.1 (95% CI 0.9 to 1.4). The OR of 3.0 (95% CI 2.5 to 3.6) recorded for prostate cancer was modified by francophone versus anglophone linguistic preference (OR 3.2, 95% CI 2.6, 3.9 versus 1.5, 95% CI 0.8 to 2.7, p = 0.02). Male sibship size was a statistically significant parameter modifying this association (p = 0.02), namely no brothers (OR 1.7, 95% CI 1.0 to 2.8), 1 or 2 (OR 3.1, 95% CI 2.2 to 4.3) and 3 or more (OR 3.9, 95% CI 2.9 to 5.2). Geographic regions of the province including and neighboring greater Montreal showed a lower OR than more peripheral regions (2.5, 95% CI 2.0 to 3.2 versus 4.1, 95% CI 2.9 to 5.7, p = 0.02).

CONCLUSIONS

Francophone men with large male sibships residing in remote areas may be at higher risk for familial prostate cancer and represent the ideal target for further efforts to determine the genetic component of prostate cancer in Quebec.

Vasectomy and prostate cancer in Québec, Canada

The present investigation measured the association between vasectomy and prostate cancer (PC) in the male population of Québec, Canada. The Québec Health Insurance Board and the Québec Cancer Registry were our principal sources of information. Lung cancer cases and the male population of Québec served as controls for comparative purposes. Within a retrospective design, our preliminary results indicate an association between vasectomy and PC. Among the 1925-39 birth cohort of individuals diagnosed with PC in 1990--93, the global odds ratio was 2.6 (95% CI=1.7--4.3) while it was compared with lung cancer as the control group. This risk increased with the length of time between vasectomy and the diagnosis of cancer. An historical design indicated strong cohesion of the results. Besides, the risk does not vary when we control for the place of residence of the individuals. Vasectomy seems to increase the risk of PC at least 10 years after the operation, but we cannot exclude the impact of a possible detection bias among vasectomized individuals.

Confirmation of prostate cancer susceptibility genes using high-risk families

Data from many types of studies support the hypothesis that strong familial components are involved in the etiology of prostate cancer. One way to access such genes is through the study of families with multiple affected family members and, in particular, families with individuals affected comparatively early in life. Several prostate cancer susceptibility loci have been described to date. Confirmation of the linkage and estimation of the proportion of families who are linked in large independent datasets is essential to understanding the significance of susceptibility genes. We explore the methodology used to perform such studies and the factors that can limit the ability to confirm linkage results. We report specifically the example of the HPC1 gene on 1q24-25.

A genome screen of multiplex sibships with prostate cancer

Analysis of a genome screen of 504 brothers with prostate cancer (CaP) who were from 230 multiplex sibships identified five regions with nominally positive linkage signals, on chromosomes 2q, 12p, 15q, 16p, and 16q. The strongest signal in these data is found on chromosome 16q, between markers D16S515 and D16S3040, a region suspected to contain a tumor-suppressor gene. On the basis of findings from previous genome screens of families with CaP, three preplanned subanalyses were carried out, in the hope of increasing the subgroup homogeneity. Subgroups were formed by dividing the sibships into a group with a positive family history (FH+) that met criteria for "hereditary" CaP (n=111) versus those which did not meet the criteria (n=119) and by dividing the families into those with a mean onset age below the median (n=115) versus those with a mean onset age above the median (n=115). A separate subanalysis was carried out for families with a history of breast cancer (CaB+ [n=53]). Analyses of these subgroups revealed a number of potentially important differences in regions that were nonsignificant when all the families were analyzed together. In particular, the subgroup without a positive family history (FH-) had a signal in a region that is proximal to the putative site of the HPC1 locus on chromosome 1, whereas the late-age-at-onset group had a signal on 4q. The CaB+ subgroup revealed a strong linkage signal at 1p35.1.

Familial and hereditary prostate cancer in southern Sweden. A population-based case-control study

The objectives of this study were to investigate the effect of family history on prostate cancer risk, to estimate the incidence of hereditary prostate cancer in southern Sweden and to assess the reliability of self-reported family history of prostate cancer. The study included consecutive prostate cancer patients and age-matched control subjects from a geographically defined population. The controls consisted of 1 male patient with malignant melanoma or non-Hodgkin's lymphoma and 1 male from the community per prostate cancer case. Family history was assessed with questionnaires, and diagnoses of fathers and brothers of cases were validated by the Southern Swedish Regional Tumour Registry. Among fathers and brothers whose names and birth dates were available, 56 (92%) of the 61 reported prostate cancer diagnoses were verified. Fifteen per cent of 356 cases and 5.0% of 712 controls reported at least 1 case of prostate cancer among their brothers or fathers, giving a relative risk of 3.2 (95% confidence interval 2.1-5.1). The relative risk increased with decreasing age at diagnosis of the patient. Based on the pedigree, 3.1% of the 356 patients were classified as having hereditary prostate cancer. This proportion was significantly higher among patients diagnosed before the age of 60 years (7.1%) than among older patients (2.2%). We conclude that there is a substantially increased risk of prostate cancer for sons and brothers of prostate cancer patients. The risk increases with decreasing age at diagnosis of the patient as an effect of a higher prevalence of hereditary prostate among early onset cases. Furthermore, we found self-reported family history of prostate cancer to be a valid estimate of the true incidence of prostate cancer in fathers and brothers of men with prostate cancer.

Familial study of prostate cancer in Jamaica

OBJECTIVES

Rates of prostate cancer in Kingston, Jamaica are extremely high (occurring in more than 300 men out of 100,000 in 1989 to 1993). This article addresses the familial aggregation of prostate cancer in Jamaica. Early evidence for familial prostate cancer was found in the Utah Mormon population. Increased risk of prostate cancer in men with a family history of prostate cancer has been consistently observed in subsequent studies. There have been few studies, however, involving black men, who are known to have an overall higher risk of developing prostate cancer.

METHODS

Two hundred sixty-three patients with prostate cancer documented by histology were studied. Two hundred sixty-three age-matched control patients were used for comparison. Extensive pedigrees were obtained for both patients with cancer and controls. Data on other malignancies including lung, breast, colon, stomach, and uterine were also collected.

RESULTS

The patients with cancer and the controls were comparable with respect to age and family size. Thirty patients with cancer had a first degree relative (ie, brother, father, or son) with prostate cancer compared to 15 controls. The odds ratio is 2.1 (95% confidence interval 1.1 to 4.4). Nine patients with cancer had a second degree relative (ie, grandfather, grandson, or uncle) affected compared to 3 controls. The odds ratio is 3.1 (95% confidence interval 0.8 to 17.8). There was no statistically significant difference in the rates of any of the other cancers studied.

CONCLUSIONS

Familial aggregation of prostate cancer is clearly evident in black Jamaican men. A man with one first degree relative with prostate cancer is twice as likely as the general population to develop prostate cancer. In addition, there may be a statistical difference in the risk of developing prostate cancer if an individual has one second degree relative affected.

Biological aggressiveness of hereditary prostate cancer: long-term evaluation following radical prostatectomy

PURPOSE

We answer the question of whether, following radical prostatectomy, prostate cancer in patients with a family history of prostate cancer relapses biochemically at the same rate as prostate cancer in appropriately matched patients with no family history.

MATERIALS AND METHODS

The study was performed in 2 parts. In both parts prostate specific antigen (PSA) progression was defined as a postoperative elevation in serum PSA greater than 0.2 ng./ml. Part 1 included 656 patients who underwent radical prostatectomy by the same surgeon. Men with a family history of prostate cancer in a father or brother (94) were compared to those with no history of prostate cancer in a father or brother (562). Part 2 comprised 52 men with a family history of prostate cancer consistent with hereditary prostate cancer (HPC). HPC is defined as a family with 3 generations affected, 3 first-degree relatives affected or 2 relatives affected before age 55 years. Each member of this HPC group was matched by postoperative Gleason score and postoperative pathological stage with a patient who also underwent radical prostatectomy in the same time frame by the same surgeon but who reported no family history of prostate cancer by telephone interview and questionnaire.

RESULTS

In part 1, 94 probands (14%) reported a history of prostate cancer in the father or in at least 1 brother. The remaining 562 probands (85%) reported no known history of prostate cancer in the father or brother(s). There was no statistically significant difference in the probability of maintaining an undetectable PSA between these 2 groups. In part 2, 45 of 52 pairs (87%) were matched identically for all matching criteria. Mean follow time for the sporadic and hereditary groups was 5.4 and 5.1 years, respectively. There was no statistically significant difference in the probability of maintaining an undetectable PSA between the 2 groups.

CONCLUSIONS

Men with an affected father or brother, or those with a family history consistent with HPC have the same outcome following radical prostatectomy as men with no family history of the disease. Combined with our previous studies, these findings suggest that there is no biologically important difference between hereditary and sporadic prostate cancers.

Familial prostate cancer in four brothers

We identified a family of 4 brothers with prostate cancer. The proband was the second son who was seen at the Department of Urology, Gunma University, Gunma, Japan, in May 1995, with a chief complaint of dysuria. The serum level of PSA was high, and a prostate needle biopsy revealed a moderately-differentiated adenocarcinoma. Subsequently, a total prostatectomy was performed. The family history revealed that the fourth son had been under treatment at the Saitama Cancer Center Hospital for prostate cancer since 1994. Therefore, the other 2 brothers became healthy male family members of the familial prostate cancer line, and their serum PSA levels were examined after obtaining their informed consent. Both had a high serum PSA level and biopsies revealed moderately-differentiated adenocarcinomas in both. Human leukocyte antigen class II gene typing was conducted on 3 of 4 brothers and 4 healthy family members who gave informed consent, and revealed the DRB1*0901-DQB1*0303 haplotype in the first, second and third sons. Familial prostate cancer is well documented in Europe and the US where the incidence of prostate cancer is high, but this is the first report of prostate cancer in 4 brothers in Japan.

Familial prostate cancer in Japan

BACKGROUND

Familial prostate cancer has been studied in Europe and the United States. This study was conducted to clarify the clinical features and incidence of the human leukocyte antigen (HLA) in familial prostate cancer in patients seen at hospitals in Japan.

METHODS

The age at diagnosis, clinical stage, histologic differentiation, prognosis, cause of death and family history were compiled from 43 patients from 20 families with familial prostate cancer (group F) and compared in patients with sporadic prostate cancer (group S). In addition, HLA class II gene typing was performed in 17 patients from 11 families with familial prostate cancer (group F') and their healthy family members (15 males and 25 females).

RESULTS

The age at diagnosis was significantly lower in group F patients (P< 0.001), but neither clinical stage nor prognosis differed between group F and group S, yet the incidence of moderately differentiated adenocarcinoma was significantly higher in group F (P< 0.01 ). There were no historical factors that were specific for group F patients. The frequency of HLA-DRB1 *0901 and *1201 alleles was significantly higher in group F' patients than in group J (the frequency of alleles in 1216 Japanese people attending the 11th Japan HLA Workshop), but not between group F' and their healthy male family members.

CONCLUSION

There were no significant differences in clinical parameters between group F and group S, except that the age at diagnosis was lower in group F patients, and that the frequency of several HLA class 11 alleles was significantly higher in patients with prostate cancer. In men with a family history of prostate cancer, examinations for early detection of prostate cancer should begin at a young age.

Significance of measurement of prostate specific antigen (PSA) in familial prostate cancer lines

The concentration of prostate specific antigen (PSA) in serum was measured in 20 brothers or sons in 10 families in which the father and son or brothers had prostate cancer using the E test TOSOH IIPA. The patients were between 32 and 70 years old with a mean age of 48.2 years. The PSA value was between 0.4 and 19.5 ng/ml with a mean value of 3.4 ng/ml. Five patients (25%) had PSA values exceeding the cut-off value of 4.0 ng/ml. After obtaining their consent, systematic prostate needle biopsy by transrectal ultrasonography was performed on 3 patients (15%). Prostate cancer was detected in all of them. Among them 2 patients were brothers, and since the other two brothers already had prostate cancer, all four brothers were confirmed to have prostate cancer. This is the first report of a familial prostate cancer in four brothers in Japan. In the western countries where the incidence of prostate cancer is higher than that in Japan, studies have been performed on the risk factors. Family history is one of the most important risk factors. In Japan, the incidence of prostate cancer is increasing rapidly. Moreover, patients with a prostate cancer family history are expected to increase. In such cases, prostate cancer screening should be performed aggressively from a young age.

Heredity and prostate cancer: a study of World War II veteran twins

BACKGROUND

Increased risk of prostate cancer among men with a family history of the disease has been observed in several epidemiological studies, and family studies have identified hereditary prostate cancer characterized by early onset and autosomal dominant inheritance.

METHODS

In this study, we examine prostate cancer heritability among twins in the NAS-NRC Twin Registry, with cases ascertained from a number of sources: recent telephone interviews, Medicare and Department of Veterans Affairs hospitalizations, previous mail questionnaires, and death certificates. A total of 1,009 prostate cancer cases were identified among the cohort of 31,848 veteran twins born in the years 1917-1927.

RESULTS

Probandwise concordance for prostate cancer was substantially higher among monozygous twin pairs, 27.1%, than among dizygous twin pairs, 7.1% (P < 0.001).

CONCLUSIONS

These data suggest that genetic influences account for approximately 57%, and environmental influences for 43%, of the variability in twin liability for prostate cancer.

Family history facilitates the early diagnosis of prostate carcinoma

BACKGROUND

Although all men age >50 years are at an increased risk for the development of prostate carcinoma, 2 major factors increase this risk: family history and race. This article outlines the influence of family history on the risk of prostate carcinoma and current understanding of factors that increase this risk.

METHODS

Published studies investigating the familial and hereditary link to prostate carcinoma are reviewed. The results of an investigation into the mendelian inheritance of prostate carcinoma are discussed as well as the relation between hereditary cancer syndromes such as breast and ovarian carcinoma and prostate carcinoma.

RESULTS

A positive family history of prostate carcinoma increases the relative risk of prostate carcinoma in male first-degree relatives approximately twofold. Prostate carcinoma is inherited as an autosomal dominant trait. The relative risk of prostate carcinoma increases with multiple affected relatives.

CONCLUSIONS

Hereditary prostate carcinoma is estimated to be associated with 43% of men in whom the diagnosis of prostate carcinoma is made at age <55 years, 34% of men in whom the diagnosis is made at age <70 years, and only 9% of men diagnosed before age 85 years. Hereditary prostate carcinoma should be suspected in families with an early age at onset of the disease and/or multiple affected family members. Because hereditary prostate carcinoma is characterized by an early age at onset, first-degree relatives in high risk families should begin screening before age 50 years.

The aetiology and pathogenesis of prostate cancer

The incidence of prostate cancer is increasing, particularly in western countries, but, despite this, its aetiology and pathogenesis remain unclear. Epidemiological studies have suggested a range of possible aetiological factors (e.g. high saturated fat intake, low intake of carotenoids, vasectomy and other sexual factors, high serum androgen levels, and a family history of prostate cancer), although results have been contradictory in many cases. A review of the literature suggests that there may be differences in the importance of these factors in younger (< 60 years) and older patients. In particular, there is growing evidence for the existence of an hereditary form of prostate cancer, with an early age of onset, an independence for dietary and other environmental factors, and an aggressive natural history. There is also increasing evidence to suggest that the pathogenesis of the disease in Japan, with its markedly different incidence rates for clinical disease (as opposed to 'latent' or 'histological' disease), may be different to that in North America. The evidence for a 'two-disease' theory of prostate carcinogenesis is discussed.

Family history of prostate cancer: a multi-center case-control study in Canada

In a population-based case-control study of prostate cancer conducted in Montreal, Toronto and Vancouver between 1989 and 1993, a total of 640 newly incident cases and 639 aged-matched population controls were interviewed as to their family history of prostate cancer as well as nutritional and other lifestyle and environmental factors. In total, 94 cases (15%) reported at least one blood relative with a family history, as compared with 32 (5%) of controls, giving a relative risk of 3.32 (95% confidence interval 2.18-5.05). The association was very consistent across all 3 centers, and was similar for each specific type of relative considered (fathers or brothers). Thus, this study provides further evidence of familial aggregation of prostate cancer, and suggests the possibility that part or all of such clustering could be related to inherited genetic patterns; if so, the availability of screening procedures for the disease offers the possibility of useful early intervention in individuals with such inherited susceptibility.

How is individual risk for prostate cancer assessed?

A man's risk of developing prostate cancer is influenced by both genetic and nongenetic factors. Genetic factors are particularly important at younger ages, and the attributable risk of strong genetic factors could be as high as 43% among men less than 55 years of age; however, only about 9% of all cases may be directly attributable to a family history of prostate cancer. Race appears to be an important determinant of risk; African-American men are at high risk, whereas men of oriental ancestry are at lower risk. The bases of these racial differences remain obscure but may be related to hormonal differences. Modifiable risk factors are most important from a public health perspective. Diet or closely related factors appear to hold the most promise for prevention, although the precise factors are unknown. The strongest evidence indicates that some component of animal fat intake appears to act as a promoter of prostate cancer. Other dietary factors, including vitamin D, vitamin E, and beta-carotene and lycopene, may confer protection, but these require more study. Many but not all studies that have examined long-term effects of vasectomy suggest that this procedure may increase risk of prostate cancer, but whether this association is causal is not established. Occupational factors, smoking, and physical activity level do not appear to be major determinants of prostate cancer risk.

Familial prostate cancer in Sweden. A nationwide register cohort study

BACKGROUND

Although prostate carcinoma is not widely recognized as a familial cancer, familial aggregation of this disease has been shown in some retrospective case-control studies. To study familial prostate cancer in Sweden, a population-based cohort study was performed, that attempted to avoid possible bias connected with some earlier studies of familial prostate cancer.

METHODS

A nationwide register cohort study was conducted using an unselected study population. The study cohort of 5496 sons of Swedish men found to have prostate cancer between 1959 and 1963 was identified through parish offices. All prostate cancer patients reported between 1958 and 1990 in this cohort were identified through linkage to the Swedish Cancer Register. The expected number of prostate cancer patients was calculated using incidence rates obtained from the same register.

RESULTS

A highly significant increased overall standardized incidence ratio (SIR) of 1.70 (95% confidence interval, 1.51-1.90) was obtained for prostate cancer in this cohort, with 302 observed cases compared with 178 expected prostate cancers. The SIR was 3.38 among patients aged 45-49 years at diagnosis, with the risk gradually decreasing to a SIR of 1.35 among patients older than 80 years (trend, P = 0.013). Among sons with a father whose prostate cancer was diagnosed at an early age (< 70 years), a significant trend (P = 0.01) for prostate cancer risk was observed due to early onset of the disease.

CONCLUSIONS

This cohort study provides further evidence that a positive family history of prostate cancer is a risk factor for developing the disease in an unselected population. The increased risk was found for all ages, but was more pronounced in younger men.

Family history and the risk of prostatic carcinoma in a high risk group of urological patients

PURPOSE

We examine the association of family history and prostatic carcinoma.

MATERIALS AND METHODS

A total of 2,968 consecutive patients referred for prostate cancer detection responded to a questionnaire and underwent transrectal ultrasound examination with or without biopsy.

RESULTS

Of the men 329 (11.1%) had a family history of prostate cancer. No differences were observed between groups with and without a family history with respect to mean patient age, serum prostate specific antigen level or biopsy rate. Prostate cancer was detected in 133 of 329 patients (40.4%) with a family history and 769 of 2,639 (29.1) with no family history (p < 0.001, odds ratio 1.7). No significant differences were observed between cancer patients with or without a family history with respect to mean Gleason score (6.0 versus 6.2), patient age at diagnosis (65.8 versus 66.7) and prostate specific antigen level (16.8 versus 17.1).

CONCLUSIONS

Patients with a family history of prostate cancer have a greater risk of the disease. In this select group of patients a positive family history was not associated with an earlier age at cancer diagnosis or a different histological grade of tumor.

Prostate cancer risk in U.S. blacks and whites with a family history of cancer

Prostate cancer occurs more frequently in U.S. blacks than whites. A population-based case-control study which investigated the association with family history of cancer was carried out among 981 men (479 black, 502 white) with pathologically confirmed prostate cancer, diagnosed between August 1, 1986, and April 30, 1989, and 1,315 controls (594 black, 721 white). Study subjects, aged 40-79, resided in Atlanta, Detroit, and 10 counties in New Jersey, geographic areas covered by population-based cancer registries. Prostate cancer risk was significantly elevated among those who reported a history of prostate cancer in first-degree relatives (O.R. = 3.2; 95% C.I.: 2.0-5.0), with blacks and whites having similarly elevated risks. These risks were unchanged by statistical adjustment for job-related socio-economic status, education, income, and marital status. Overall, the ORs associated with history of prostate cancer in fathers and brothers were 2.5 (95% C.I.: 1.5-4.2) and 5.3 (95% C.I.: 2.3-12.5), respectively. Risks associated with a family history of prostate cancer were consistently elevated among younger and older subjects. Only small non-significant excesses of prostate cancer risk were associated with a family history of breast, colorectal, or other cancers. While familial occurrence is a key risk factor for prostate cancer and likely to be genetically based, the similar familial risks among blacks and whites suggest that the ethnic disparity in incidence is influenced by environmental factors.

Benign and malignant prostatic neoplasms: human studies

Because the present ability to treat and cure patients with prostate cancer is limited to those patients with pathologically organ-confined disease, it has become increasingly important to diagnose this disease at an early stage, when cure is most likely. Recent advances in imaging may allow the urologist and the pathologist to make the diagnosis of prostate cancer much earlier in the natural course of the disease. It therefore becomes imperative to have methods available to predict which patients have a high probability of progressing so that treatment can be assigned logically and appropriately. Our current methods of prognosis determination (stage and grade) do not allow accurate assessment of tumor behavior in the majority of individual patients with prostate cancer. Therefore, more accurate quantification of nuclear and cellular changes that take place as a tumor progresses to take on the aggressive (metastatic) phenotype are urgently needed. Experimental techniques have proven useful in answering these questions and now seem ready for large-scale testing in clinical studies.

Recessive oncogenes

Tumor-suppressor genes (antioncogenes or recessive oncogenes) are cancer genes that achieve their oncogenic effect by mutational inactivation of both normal alleles. By contrast, oncogenes are created from protooncogenes by mutations that lead to aberrant functional activation. Mutation of multiple suppressor genes and/or oncogenes probably is required for the genesis of most human neoplasms. Two well-characterized tumor-suppressor genes, the retinoblastoma gene (rb) on chromosome 13q and p53 on chromosome 17p, frequently are mutated in a broad range of human cancer types. Mutations of these genes have been documented in prostate carcinoma but appear to affect only a subset of cases. Nevertheless, as in other cancers, introduction of normal copies of rb or p53 suppresses the neoplastic properties of prostatic tumor cells carrying mutated alleles of the relevant gene. These results suggest that mutation of rb or p53 is involved in the genesis or progression of some prostate cancers. Frequent allelic losses of certain chromosome arms (especially 8p, 10p and q, and 16q) from prostatic cancer cells may indicate the involvement of novel suppressor genes located in these regions. Although the inactivation of suppressor genes appears to be a common genetic mechanism in human oncogenesis, the rates of mutation of particular genes vary widely with the type of cancer. It is unknown whether prostate cancers with or without mutation of rb, p53, or other suppressor loci differ biologically or prognostically; this is an area of active investigation. Fundamental understanding of the genetic lesions that occur during human oncogenesis has great potential for clinical application in diagnosis, prognosis, and therapy.