Review: prostate cancer epidemiology

Occupational Risk Factors for Prostate Cancer: A Meta-analysis

Prostate cancer is the second most common cancer in men worldwide. There are many occupational factors that have been suggested to cause prostate cancer. Our aim was to evaluate the evidence for causality by a literature review of occupational factors. We searched literature in Medline and SCOPUS from 1966 to June 30, 2015 to identify occupational risk factors for prostate cancer. The following risk factors were selected: farmers/agricultural workers, pesticides - whole group, and separately organophosphate and organochlorine pesticides, carbamates and triazines, cadmium, chromium, cutting fluids, acrylonitrile, rubber manufacturing, whole body vibration, shift work, flight personnel, ionizing radiation, and occupational physical activity. For each factor a literature search was performed and presented as meta-analysis of relative risk and heterogeneity (Q and I2 index). A total of 168 original studies met the inclusion criteria with 90,688 prostate cancer cases. Significantly increased risks were observed for the following occupational exposures: pesticides (metaRR = 1.15, 95% confidence interval [CI] = 1.01-1.32; I2 = 84%), and specifically group of organochlorine pesticides (meta relative risk [metaRR] = 1.08, 95% CI = 1.03-1.14; I2 = 0%), chromium (metaRR = 1.19, 95% CI = 1.07-1.34; I2 = 31%), shift work (metaRR = 1.25, 95% CI = 1.05-1.49; I2 = 78%) and pilots (metaRR = 1.41, 95% CI = 1.02-1.94; I2 = 63%) and occupational physical activity in cohort studies (metaRR = 0.87, 95% CI = 0.81-0.94; I2 = 0%). The literature review supports a causal association for a few of the previously suggested factors.

Milk and Dairy Product Consumption and Prostate Cancer Risk and Mortality: An Overview of Systematic Reviews and Meta-analyses

Milk and dairy product consumption has been associated with an increase in prostate cancer risk; however, discrepancies have been observed in the literature. This first overview of systematic reviews and meta-analyses was carried out with the main objective of compiling and discussing the evidence generated to date related to milk and dairy product consumption and prostate cancer risk and mortality. A systematic search in MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials, the Cochrane Database of Systematic Reviews, and the Web of Science (from inception to 30 April 2018) was conducted. The inclusion criteria were as follows: adult men, meta-analyses of longitudinal studies, dairy product consumption, and risk of prostate cancer or related outcomes. The AMSTAR2 checklist was used to evaluate methodological quality. The synthesis methods included dairy product exposure (high compared with low consumption or dose-response), dairy product type (total dairy products, milk, cheese, yogurt, and others), and prostate cancer outcomes (total, nonadvanced, and advanced prostate cancer and mortality) displayed in forest plots. Six meta-analyses were identified. These studies reported on the analysis of the 2 to 32 cohorts (up to 848,395 subjects/38,107 cases; 4-28 y of follow-up) and 2 case-control meta-analyses (12,435 subjects). The meta-analysis quality was valued as mostly "good" according to the AMSTAR2 criteria. All RRs of high compared with low consumption (dose-response) for total prostate cancer ranged from 1.68 to 1.09 (1.07 per 400 g/d) for total dairy products, 1.50 to 0.92 (1.06 to 0.98 per 200 g/d) for milk (whole, low-fat, and skim milk considered separately), and 1.18 to 0.74 (1.10 per 50 g/d) for cheese. RRs have decreased since the first meta-analysis. Statistical heterogeneity generates uncertainty in the observed results (up to I2 = 77.1%). In conclusion, although there are some data indicating that higher consumption of dairy products could increase the risk of prostate cancer, the evidence is not consistent. This review was registered with PROSPERO as CRD42018094737.

Adiponectin as a Potential Therapeutic Target for Prostate Cancer

Adipokines are bioactive proteins that mediate proliferation, metabolism, inflammation, and angiogenesis. Adiponectin is an important adipokine that exerts multiple key functions via its anti-metabolic syndrome and anti-inflammatory properties. A number of adiponectin receptors, AdipoR1, AdipoR2 and T-cadherin, have been identified. Recent studies have suggested the involvement of adiponectin and receptors in several cancers, including prostate, breast, endometrial, brain, and colon cancer. Altered levels of adiponectin expression, or its interacting receptors, in cancers can lead to dysregulation of signaling pathways. Our current review describes the molecular mechanisms underlying the anti-tumorigenesis activity of adiponectin and the role of its receptors in prostate carcinogenesis, and provides perspectives of adiponectin-mediated signaling as a potential target for therapy.

Review of cadmium transfers from soil to humans and its health effects and Jamaican environment

Concerns about the effects of cadmium on human health have led to numerous guidelines and regulations limiting its concentrations in soils and food and allowable human intakes. These have socio-economic consequences in terms of land use and the marketing of food. The bauxite soils in Jamaica, which are both aluminium ores and agricultural soils contain orders of magnitude higher than world normal concentrations of cadmium resulting in elevated Cd concentrations in several foodstuffs and significant transfers to humans, which would seem to represent a risk factor for increased mortality and/or morbidity in the local populations. But, as in Shipham and other examples, there is no evidence of cadmium-related human distress. Macro-indicators like life expectancy and median ages of death do not show cadmium related geographical distributions. The present review focuses on the soils and foods and illnesses of high incidence especially cancers and renal disease that have been traditionally associated with cadmium. In view of the remarkable concentrations of cadmium involved in Jamaica, and often contradictory reports in the literature, it appears that much remains to be learned about certain details of cadmium toxicity.

The use of herbal and over-the-counter dietary supplements for the prevention of prostate cancer

Having a high probability of experiencing prostate cancer during their lifetime, men are increasingly seeking protection against this disease with the use of over-the-counter dietary supplements containing herbs, vitamins, or plant-derived biochemical agents. The use of these agents for prostate cancer prevention is driven by epidemiology supporting the idea that regional diets and consumption of specific dietary components (certain herbs, vitamins, isoflavones, and polyphenols) are associated with a lower risk for prostate cancer, in conjunction with basic research that is defining molecules within food substances that kill or suppress growth of cultured human prostate cancer cells. Moreover, there is a sense that these dietary agents lack side effects, although this assumption often is faulty. Unfortunately, at this time, there is insufficient clinical evidence to support the widespread use of these dietary supplements for chemoprevention of prostate cancer, although ongoing clinical trials of the most promising vitamins and minerals are approaching conclusion.

The use of herbal and over-the-counter dietary supplements for the prevention of prostate cancer

Having a high probability of experiencing prostate cancer during their lifetime, men are increasingly seeking protection against this disease with the use of over-the-counter dietary supplements containing herbs, vitamins, or plant-derived biochemical agents. The use of these agents for prostate cancer prevention is driven by epidemiology supporting the idea that regional diets and consumption of specific dietary components (certain herbs, vitamins, isoflavones, and polyphenols) are associated with a lower risk for prostate cancer, in conjunction with basic research that is defining molecules within food substances that kill or suppress growth of cultured human prostate cancer cells. Moreover, there is a sense that these dietary agents lack side effects, although this assumption often is faulty. Unfortunately, at this time, there is insufficient clinical evidence to support the widespread use of these dietary supplements for chemoprevention of prostate cancer, although ongoing clinical trials of the most promising vitamins and minerals are approaching conclusion.

Associations between coronary heart disease, obesity and histological prostate cancer

OBJECTIVE

The present study investigates the possible associations between coronary heart disease and histological prostate carcinoma in autopsy material.

MATERIAL AND METHOD

The material of our study, were 116 men between 55 years and 98 years of age, who died in the period of August 2002-January 2005. The initial segment of the aorta and the prostate glands of all cadavers were removed while the initial 30 mm of the left and right coronary arteries and the peripheral zone of the prostate gland underwent pathologic examination.

RESULTS

Of all subjects examined 71.8% had pathological findings suggesting advanced coronary heart disease. Twenty out of 116 cadavers were found with histological carcinoma in their prostate specimen. Among subjects positive for prostate cancer, 12 had died of cardiovascular diseases, while 16 had macroscopic evidence of advanced coronary artery obstructive disease, a finding that was confirmed on pathologic examination. Although most of the subjects had atheromatous lesions on the coronary arteries, the percentage of men with prostate cancer, which had advanced atheromatosis, was greater when compared to those of subjects without prostate cancer. The relation between the coronary artery obstructive disease severity and the presence of latent prostate cancer was statistically significant (P = 0.02). No statistically significant correlation was obtained between body mass index and the presence of prostate cancer.

CONCLUSIONS

Our results indicate that there could be an association between coronary artery obstructive disease and prostate cancer, however due to the relatively low sample further studies are needed in order to confirm such findings.

Garlic Compound, Diallyl Disulfide Induces Cell Cycle Arrest in Prostate Cancer Cell Line PC-3

Prostate cancer is the most predominant cancer in men and related death rate increases every year. Till date, there is no effective therapy for androgen independent prostate cancer. Previous studies reported that aged garlic extract suppresses cancer growth. In the present study, diallyl disulfide [DADS], oil soluble organosulfur compound of garlic, was studied for its antiproliferative and induction of cell cycle arrest on prostate cancer cells in vitro. The suppression of cell growth was assessed by MTT assay. Induction of cell cycle arrest was assessed and confirmed by propidium iodide staining in flowcytometric analysis and western blotting analysis of major cell cycle regulator proteins. The results showed that DADS inhibited the growth of prostate cancer cells in a dose dependent manner, compared to the control. At 25 microM and 40 microM concentrations, DADS induced cell cycle arrest at G2/M transition in PC-3 cells. Western blotting analysis of cyclin A, B(1) and cyclin dependent kinase 1 [CDK1] revealed that DADS inhibited the cell cycle by downregulating CDK1 expression. It is concluded that DADS, inhibits proliferation of prostate cancer cells through cell cycle arrest. Dose dependent effect of DADS on PC-3 cell line was observed in the present study.

Inhibition of 17beta-hydroxysteroid dehydrogenases by phytoestrogens: comparison with other steroid metabolizing enzymes

Effects of phytoestrogens on human health have been reported for decades. These include not only beneficial action in cancer prevention but also endocrine disruption in males. Since then many molecular mechanisms underlying these effects have been identified. Targets of phytoestrogens comprise steroid receptors, steroid metabolising enzymes, elements of signal transduction and apoptosis pathways, and even the DNA processing machinery. Understanding the specific versus pleiotropic effects of selected phytoestrogens will be crucial for their biomedical application. This review will concentrate on the influence of phytoestrogens on 17beta-hydroxysteroid dehydrogenases from a comparative perspective with other steroid metabolizing enzymes.

Flavonoid inhibition of overexpressed human 3beta-hydroxysteroid dehydrogenase type II

The inhibitory effects of various flavonoids on human 3beta-hydroxysteroid dehydrogenase/Delta(5)-Delta(4)-isomerase type II (3beta-HSD type II), overexpressed in baculovirus, were investigated, and the structure-inhibition relationship was examined. The isoflavone derivatives daidzein, genistein, formononetin and biochanin A inhibited 3beta-HSD type II activity at a concentration of 10 microM and of these, genistein was the most potent inhibitor. 6-Hydroxyflavone (6-HF), a synthetic flavone, also strongly inhibited 3beta-HSD activity but 5-HF, 7-HF and other natural flavones were less potent. Energy minimization structures of the flavonoids, as produced using MOE software, showed that isoflavones and flavones have an almost flat A-C ring structure, and that flavonoids that acted as inhibitors had similar steric structures to DHEA. Genistein, 6-HF and cyanoketone, which is known as a typical 3beta-HSD inhibitor, were found to act as competitive inhibitors with K(i) values of 0.12 microM, 0.19 microM and 0.67 nM, respectively. Furthermore, the LUMO (lowest unoccupied molecular orbital (LUMO)) values, as calculated using WinMOPAC (Fujitsu, Japan), of the inhibitors were correlated with the IC(50) values (r2 = 0.84). From these results, it appears that inhibitory effects of flavonoids are due to the combination of steric structure and electron affinity between the active center of 3beta-HSD type II and the flavonoid molecule.

Human 17beta-hydroxysteroid dehydrogenase type 5 is inhibited by dietary flavonoids

Phytoestrogens contained in a vegetarian diet are supposed to have beneficial effects on the development and progression of a variety of endocrine-related cancers. We have tested the effect of a variety of dietary phytoestrogens, especially flavonoids, on the activity of human 17beta-hydroxysteroid dehydrogenase type 5 (17beta-HSD 5), a key enzyme in the metabolism of estrogens and androgens. Our studies show that reductive and oxidative activity of the enzyme are inhibited by many compounds, especially zearalenone, coumestrol, quercetin and biochanin A. Among flavones, inhibitor potency is enhanced with increased degree of hydroxylation. The most effective inhibitors seem to bind to the hydrophilic cofactor binding pocket of the enzyme.

Diet and prostate cancer

The importance of dietary factors for prostate carcinogenesis has been proven by epidemiological studies of immigrants from Asia into the USA. Intake of foodstuffs rich in fat, including meat, is suggested to be a risk factor. Experimentally, while some studies demonstrated high fat intake to promote rat prostate carcinogenesis, others did not. Charcoal-cooked red meat and fish have been demonstrated to contain heterocyclic amines that are carcinogenic in rodents and non-primates. Among them, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) has been shown to induce cancers in the mammary glands, colon and prostate of rats. Although there are epidemiological data showing that PhIP could contribute to the development of breast cancer, equivalent evidence for prostate cancer is lacking. However, as protective dietary factors, micronutrients such as selenium, zinc, isoflavones, carotenoids and lycopenes and vitamins E and D have been listed. Animal experimentation on prostate cancer has consistently supported preventive potential for carotenoids and isoflavones, in contrast to the inconsistent results with high fat diets. Although the diet has apparently an important influence on prostate carcinogenesis in man, further research is necessary for clarification of specific factors in man.

Genistein and vitamin D synergistically inhibit human prostatic epithelial cell growth

We performed studies to test synergism between the growth inhibitory effects of genistein and vitamin D compounds on prostatic epithelial cells. Isobolographic analysis demonstrated that genistein, in combination with the hormonally active form of cholecalciferol, 1alpha,25-dihydroxycholecalciferol, synergistically inhibited the growth of primary human prostatic epithelial cells (HPEC) and prostate cancer cells. Synergistic growth inhibition of HPEC was also observed between genistein and the low-calcemic vitamin D compound 25-hydroxycholecalciferol. Flow cytometry with HPEC indicated that genistein induced arrest in the G(2)M phase, whereas 1alpha,25-dihydroxycholecalciferol or 25-hydroxycholecalciferol induced arrest in the G(1/0) phase of the cell cycle. Combining genistein with either vitamin D compound resulted in both G(2)M and G(1/0) arrest in HPEC. In contrast, flow cytometry of prostate cancer cells indicated that both genistein and 1alpha,25-dihydroxycholecalciferol induced a G(1/0) arrest either alone or in combination. These are the first studies that demonstrate synergism between the prostatic cell growth inhibition elicited by genistein and that elicited by vitamin D compounds.

Phytoestrogens inhibit human 17beta-hydroxysteroid dehydrogenase type 5

The 17beta-hydroxysteroid dehydrogenase type 5 (17beta-HSD 5) is involved in estrogen and androgen metabolism. In our study we tested the influence of environmental hormones, such as phytoestrogens (flavonoids, coumarins, coumestans), on reductive and oxidative 17beta-HSD activity of the human 17beta-hydroxysteroid dehydrogenase type 5 (17beta-HSD 5). These dietary substances were shown to be potent inhibitors of aromatase, different 17beta-HSDs and seem to play an important role in delay of development of hormone dependent cancers. Our studies show that reductive and oxidative activity of the enzyme are inhibited by many dietary compounds, especially zearalenone, coumestrol, quercetin and biochanin A. Among the group of flavones inhibitor potency is growing with increasing number of hydroxylations. We suggest that these substances are bound to the hydrophilic cofactor-binding pocket of the enzyme. An interesting inhibition pattern is observed for 18beta-glycyrrhetinic acid, which has no influence on the oxidative but only on the reductive reaction. This indicates that this substrate binds to pH- and cofactor-depending sites at the active center of the enzyme.

Experimental prostate carcinogenesis - rodent models

A number of rodent models of prostate carcinoma development have been established to study mechanisms and modifying potential. All except for transgenic mouse models need long experimental periods for generation of a high yield of cancers. Spontaneous prostate tumor models, while not practical in terms of time and tumor incidences, allow the natural course of multistep neoplasia to be followed without a need for chemical exposure. Carcinogens, especially in combination with testosterone, can induce prostate carcinomas in rats, but none are prostate-specific, so that tumor development in other organs is a complicating factor. Induction of invasive prostate carcinomas in the rat frequently requires long-term administration of a pharmacological dose of testosterone with or without application of a chemical carcinogen. While there are several transgenic mouse models, each also has strong and weak points, and it is therefore necessary to select the best model for the purpose of any experimental study.

Estrogen receptor expression in prostate cancer and premalignant prostatic lesions

Estrogens have been implicated in prostatic cancerogenesis and tumor progression. The mechanisms underlying estrogen signaling in human prostate tissue, however, remain poorly understood. Using immunohistochemical and in situ hybridization (ISH) techniques, the present study demonstrates the classical estrogen receptor (ERalpha) in premalignant lesions and prostatic adenocarcinoma through the various stages of the disease. Conversely, the novel characterized ERbeta subtype was undetectable in human prostate tissue. High-grade prostatic intraepithelial neoplasia revealed ERalpha mRNA and protein expression in 28% and 11% of cases evaluated. Focal ER immunoreactivity was detected in a minority of low- to intermediate-grade adenocarcinoma. High-grade (primary Gleason grade 4 and 5) tumors revealed ER protein expression in 43% (62% respectively) of cases. The most significant ERalpha gene expression on mRNA and protein levels was observed in hormone refractory tumors and metastatic lesions, including lymph node and bone metastases. Results of the current study suggest that estrogens can affect prostatic cancerogenesis and neoplastic progression through an ER-mediated process in human prostate tissue.

Prostate cancer screening: promise and peril--a review

This review summarizes the current status of and recommendations for prostate cancer screening with prostate-specific antigen in light of recent reductions in prostate cancer incidence and mortality. It describes how the uncertain effectiveness of aggressive treatment for prostate cancer and a reservoir of unsuspected indolent cancers make prostate cancer fit poorly into conventional screening models. The large proportion of men with unsuspected prostate cancers that may not cause morbidity or mortality and are unlikely to benefit from aggressive treatment decrease the effectiveness of a screening program. In addition, indolent, unsuspected prostate cancers in the screening population accentuate the detrimental effects of length bias on studies evaluating the effectiveness of prostate cancer screening. Screening tests for prostate cancer will continue to improve, but chemoprevention or nutritional prevention with vitamins and micronutrients such as tocopherols or selenium may prove to be effective methods of reducing prostate cancer incidence and should be aggressively investigated.

Adjusted odds ratios under nondifferential misclassification: application to prostate cancer

The high prevalence of unsuspected prostate cancer among middle-aged and elderly men is unique among cancers. With their uncertain natural history, unsuspected prostate cancer cases may be misclassified into control groups in which they can obscure the identification of prostate cancer risk factors in case-control studies. Assuming that the exposure experience of diagnosed and of unsuspected prostate cancers is the same (nondifferential misclassification), case-control odds ratios are biased toward the null, which may provide a rationale for reexamining findings in negative case-control studies of prostate cancer. This article reviews the evidence supporting a high prevalence of prostate cancer and describes formulae that can be used to adjust for misclassification bias in completed case-control studies and to estimate required sample sizes in proposed studies.

Inhibitory effects of soy and rye diets on the development of Dunning R3327 prostate adenocarcinoma in rats

METHODS

Dunning R3327 PAP prostate tumors were transplanted in 125 rats, the rats were divided into five groups, and tumor development was examined for 24 weeks during treatment with diets containing 33% of soy flour (SD), rye bran (RB), heat-treated rye bran (HRB), or rye endosperm (RE).

RESULTS

In the SD, RB, and HRB groups, significantly fewer palpable tumors and lower tumor volume were detected 14 and 16 weeks after transplantation when compared with the control, fiber-free dietary (FF) group. The body weight was lower 16 weeks after tumor transplantation in the RB and HRB groups when compared with the control group (P < 0.05). Rats in the RB and the HRB groups had a significant lower energy intake than the FF group during the first metabolic observation period, 3-6 weeks after tumor transplantation (P < 0.05), whereas the energy intake was the same in all groups during the second metabolic observation period, 13-16 weeks after tumor transplantation. However, when the tumor volume was adjusted for the body weight of the animals, there were still significant lower tumor volumes in the SD, RB, and HRB groups compared with the FF group (P < 0.05). A significant increase in daily urinary excretion of the isoflavonoids, daidzein, O-desmethylangolensin, equol, and Genistein, was observed in the rats fed SD, and of the ligands enterolactone and enterodiol in the rats fed RB and HRB during both metabolic periods. There were no differences in testosterone levels between the groups.

CONCLUSIONS

The present study shows that SD inhibits implanted prostate cancer growth. Although RB and HRB had a protective effect, further studies are needed to exclude the possibility that a low energy intake played a role in this respect. The results suggest that phytoestrogens (isoflavonoids and ligands), may be responsible for the delayed prostate tumor growth.

Parenteral polyoestradiol phosphate vs orchidectomy in the treatment of advanced prostatic cancer. Efficacy and cardiovascular complications: a 2-year follow-up report of a national, prospective prostatic cancer study. Finnprostate Group

OBJECTIVE

To evaluate the clinical efficacy and cardiovascular complications of orchidectomy or polyoestradiol phosphate (PEP) in the treatment of advanced prostatic cancer.

PATIENTS AND METHODS

In a prospective, randomized study 444 patients (mean age 73 years, range 45-91) with T3-4 M0 or T1-4 M1 prostatic cancer were treated either by orchidectomy (group 1, n = 217) or parenteral PEP (group 2, n = 227; 240 mg/month). The patients were examined at 3 and 6 months after start of the therapy and thereafter every 6 months; they were also assessed whenever they had symptoms indicating progression. Possible cardiovascular complications included myocardial infarction, cerebrovascular accident, pulmonary embolism and deep vein thrombosis.

RESULTS

After a follow-up of 2 years there was no statistically significant difference between the groups in progression-free time; 65 of 217 (30%) patients in group 1 showed evidence of progression, including seven (3%) who died from prostate cancer. In group 2, 64 of 227 (28%) patients showed progression and eight (3.5%) died from prostatic cancer. There were 10 (5%) cardiovascular complications in patients in group 1, including five (2%) cardiovascular deaths; in group 2 there were 24 (11%) and 14 (6%), respectively. During the first year of treatment there were three (1.4%) cardiovascular complications in group 1 and 14 (6%) in group 2 (P < 0.05), and during the second year, seven (4%) and 10 (6%), respectively.

CONCLUSION

Parenteral PEP (240 mg/month) seems to be as efficient as orchidectomy in inhibiting disease in patients with advanced prostatic cancer (T3-4 M0 and T1-4 M1). There were more cardiovascular complications in patients treated with PEP than after orchidectomy; the difference was statistically significant during the first year of treatment.

Cancer of the prostate: a nutritional disease?

In summary, epidemiologic and laboratory evidence increasingly demonstrate that nutritional factors, especially reduced fat intake, soy proteins, vitamin E derivatives, and selenium, may have a protective effect against prostate cancer. The experimental observation that low-fat diets and soy protein extracts may influence the progression of established tumors, rather than inhibiting etiologic factors, is particularly intriguing because it may serve to help explain the paradox whereby the incidence of clinical prostate cancer shows wide geographic variation, yet the evidence persists that the incidence of microfocal tumors is essentially the same worldwide. These observations, plus the likelihood that nutrition trials are likely to have little in the way of toxicity that would preclude their completion, argue that such trials should be performed. It is estimated that 30% to 50% of human malignancies may be related to dietary factors, and although the feasibility of trials involving low-fat diets has been proved in ongoing trials for colon and breast cancer, no similar study exists for prostate malignancy. Critics of epidemiologic research argue that data derived from case-control studies are subject to recall bias and are thus artifactual. Indeed, many researchers now believe that the breast cancer-dietary fat hypothesis has been discredited. The major difference between the prostate cancer and breast cancer literature is the remarkable consistency of the cohort studies. In these studies, exposure is determined prospectively and is therefore free from recall bias. In this sense they more closely resemble a clinical trial. The majority of cohort studies involving dietary fat and breast cancer have been negative. We believe that these data justify large-scale trials in the area of prevention of prostate cancer. One such proposed study already submitted for National Institutes of Health funding from a consortium of centers is the Prostate Interventional Nutrition Study (PINS), modeled after the Women's Interventional Nutrition Study, which investigates the effect of low-fat diets in women receiving therapy for node-positive breast cancer. The PINS study will be limited to men who have detectable serum PSA levels but no other clinical evidence of disease after radical prostatectomy. All subjects will receive nutritional guidance, with randomization between a control arm receiving the currently recommended 30% fat diet and an interventional arm in which a 15% fat diet is supplemented with soy protein, vitamin E, and selenium. The end points for evaluation will be compared with progression based on changes in PSA and the time of onset of clinical, as opposed to biochemical, disease. Single-institution trials involving groups thought to be at high risk of developing clinical cancer--including men with persistently elevated PSA levels, two negative prostate biopsies, high-grade prostatic intraepithelial neoplasia on biopsy, and a strong family history of prostate cancer--are being initiated at MSKCC and other institutions.

CONCLUSIONS

We have reviewed the evidence that nutritional factors play a role in the progression rate of prostate cancer and may help to explain the geographic variation in the incidence observed. However, without well-controlled prospective trials, the attractive hypothesis that nutrition plays a role in tumor progression remains simply an attractive hypothesis. To date, no definite proof of a preventive effect has been shown in a study that will withstand rigid scientific scrutiny. The opportunity exists, however, for the urologic community, working together with experts in the area of nutrition, not only to advance our understanding of prostate tumorigenesis, but to rebut those critics of modern medical technology who claim that we have ignored the total or holistic approach to healing. (ABSTRACT TRUNCATED)

The indications, rationale, and results of neoadjuvant androgen deprivation in the treatment of prostatic cancer: Memorial Sloan-Kettering Cancer Center results

OBJECTIVES

The use of neoadjuvant chemotherapy prior to definitive surgery has been firmly established in other areas of oncology, most notably in the treatment to testis and Wilm's tumors. The use of neoadjuvant androgen deprivation therapy (ADT) in conjunction with radical prostatectomy remains a source of controversy. We have conducted phase II and phase III studies to assess the effects of 3 months of preoperative ADT (goserelin and flutamide) on the pathologic staging and postsurgery prostate-specific antigen (PSA) relapse rate. We also reviewed the data confirming the understaging of clinically localized prostatic cancer and the experimental data providing the conceptual support for ADT.

METHODS

We report the results of 141 patients, Stage T0-T0, in a Phase II study with concurrent, nonrandomized controls (N = 72) versus a treatment arm (N = 69) of men receiving 3 months of ADT with 3.6 mg goserelin for 28 days and 750 mg flutamide daily. We also report the interim results in 114 men participating in a prospective, randomized study of ADT versus surgery alone.

RESULTS

The 69 patients who received 3 months of goserelin and flutamide followed by radical prostatectomy had a pathologic organ-confined cancer rate of 74%, versus 48% in the control group who received no ADT prior to surgery. The margin-positive rate was 10% in the ADT group versus 33% in the control group. In an interim analysis of 114 patients (59 ADT, 55 control), the organ-confined and margin-positive rates were 73% and 17% in the ADT group versus 56% and 36% in the control arm, respectively. The PSA disease-free rate at a mean follow-up of 28.6 months (range 6.2 to 49.5 months) was 89% in the ADT-treated patients (N = 98) and 84% in the control patients (N = 96). There was no statistical difference demonstrated between the arms with respect to biochemical failure.

CONCLUSIONS

While the pathologic staging of tumors following ADT treatment was improved compared with surgical controls, to date the PSA disease-free survival rates are similar. Patients with residual extracapsular (P3) disease after ADT manifest an increased PSA failure rate compared with those with P3 tumors treated by surgery alone. This suggests that ADT may identify a subset of patients with aggressive tumors that may be candidates for additional therapeutic interventions even before PSA failure occurs.

Epidemiological characteristics of prostate cancer in Gunma Prefecture, Japan. Gunma University Urological Oncology Study Group

BACKGROUND

Prostate cancer is rare in Asia, but the number of patients is increasing in Japan. We conducted an epidemiological study of prostate cancer in Gunma Prefecture, Japan, to investigate the trends and characteristics of the disease.

METHODS

The subjects were 1,411 prostate cancer patients newly diagnosed between 1985 and 1992, and 656 patients who died from prostate cancer between 1981 and 1992. The incidence and mortality rates were calculated by year, demographic region and age.

RESULTS

The yearly incidence rate showed an increase but the mortality rate showed no marked fluctuations. There was no significant difference between urban and rural districts in either incidence or mortality rate. The incidence rate tended to be high in the northern part of the prefecture, but no marked variation in mortality rate was seen. The incidence and mortality rates in districts with a history of manganese mining were high compared to those in districts without mining. In contrast, the incidence and mortality rates in districts with a history of zinc mining were comparatively lower. Both incidence and mortality rates showed a marked increase with age. The age-specific incidence showed a double logarithmic relationship to age.

CONCLUSIONS

The increase of the yearly incidence rate might be due to changes in lifestyle and environmental factors, improved diagnostic techniques, and increased awareness among the general public regarding prostate disease. Further investigation is needed to clarify the pattern and the causes of regional differences in the incidence and mortality rates. The possibilities that managanese and zinc might be related to prostatic carcinogenesis are suggested.

Cadmium and prostate cancer

Prostatic cancer is a common and frequently lethal malignant disease. In the United States and other countries the incidence and mortality rate of prostate cancer continue to rise. Cancer of the prostate has an extremely complex etiology and appears dependent on a variety of factors, making linkage to a single factor very difficult to detect. Cadmium is a metallic toxin of great environmental and occupational concern. Cadmium exposure has been associated with human prostatic cancer in some, but not all, epidemiologic studies. Some studies indicate that tissue levels of cadmium in the human prostate correlate with malignant disease. Any association between cadmium and prostatic cancer has been controversial, in large part because of a previous lack of relevant animal models. However, several chronic studies in rats revealing a correlation between cadmium exposure and prostatic tumors have been published over the last several years. These include a study of oral cadmium exposure, a route extremely relevant to human exposure. Several of these chronic studies indicate a hormonal dependence of cadmium-induced prostate cancer. Other supportive work continues to accumulate, such as studies showing in vitro malignant transformation of prostatic epithelial cells with cadmium exposure. In addition, there are indications that the primary biologic tolerance system for cadmium (i.e., the metallothionein gene) may be only poorly active in the specific lobes of the rat prostate in which cadmium induces tumors. The induction in rats of prostate cancer by cadmium treatment clearly supports, but does not definitively establish, a possible role for cadmium as an etiological agent in human prostate cancer. Further research, however, will be required to establish the precise role of cadmium in this important human malignancy.

Sex hormone-induced nuclear DNA damage and lipid peroxidation in the dorsolateral prostates of Noble rats

To date, few studies have been reported on any aspect of DNA damage in organs of intact animals. We and others demonstrated induction of high incidences of dysplasia, a precancerous proliferative lesion, and adenocarcinoma selectively in the dorsolateral prostates (DLPs) of Noble rats exposed to a long-term combined testosterone and estradiol-17 beta treatment (T + E2-treatment). We here report induction of a significant increase in DNA strand breakage and accumulation of lipid peroxidation fluorescent products in the DLPs, but not in the ventral prostates (VPs), of rats treated with T + E2 for 16 weeks. These results indicate that this dual hormone treatment has free radical-based DNA damaging effect on rat DLP and therefore may have tumor-initiating action. Since a similar effect was not observed in regenerating DLPs of castrated rats following testosterone replacement, we conclude that the genotoxic effect of the dual hormone treatment is a direct result of hormone action and not secondarily due to enhancement of cell proliferation.

Smoking and drinking habits in relation to prostate cancer

OBJECTIVE

To evaluate the role of tobacco and alcohol consumption in the aetiology of prostate cancer.

PATIENTS AND METHODS

In a case-control study conducted in the Netherlands, information on smoking and drinking habits was obtained from questionnaires completed by 345 patients exhibiting primary prostate cancer and by 1346 controls with benign prostate hyperplasia. The response rate was 79%.

RESULTS

No association was observed between drinking habits and the risk of prostate cancer (324 cases versus 1237 controls; odds ratio 1.36; 95%CI 0.84-2.22). A significantly elevated odds ratio was found for individuals who had smoked at any time during their lives (329 cases versus 1212 controls; odds ratio 2.12; 95%CI 1.24-3.62). However, no relationship was observed between the number of cigarettes smoked, the duration of smoking, the age at which the subjects started smoking or with the calendar period in which they were born. Odds ratios calculated for individuals who smoked in consecutive 5-year periods between 1940 and 1989 did not show any trend. Furthermore, the risk of prostate cancer among ex-smokers did not differ significantly from the risk among current smokers, even when smoking was stopped more than 25 years previously.

CONCLUSION

From these findings, which do not point to the causative agent, it would appear that neither smoking nor alcohol consumption seriously increases the risk of prostate cancer.

Developmental estrogenization and prostatic neoplasia

The association of estrogens with benign prostatic hyperplasia and prostatic cancer has been widely studied, but no conclusive evidence exists for a role of estrogens in prostatic disease. This paper reviews the literature and describes studies which have sought to show a correlation of estrogens and alterations in the prostates of humans and experimental animal models. Using the developmentally estrogenized mouse model, we propose an alternative role for estrogens as a predisposing factor for prostatic diseases: estrogen exposure during development may initiate cellular changes in the prostate which would require estrogens and/or androgens later in life for promotion to hyperplasia or neoplasia. Thus, the critical time for estrogen action would be during the development of the prostatic tissue. We further suggest that estrogen-sensitive cells may remain in the prostate and be more responsive to estrogens later in life or less responsive to the normal controlling mechanisms of prostatic growth.

Enhancing effect of cadmium on rat ventral prostate carcinogenesis induced by 3,2'-dimethyl-4-aminobiphenyl

The effects of cadmium given at different stages during 3,2'-dimethyl-4-aminobiphenyl (DMAB)-induced rat prostate carcinogenesis were investigated using male F344 rats. Animals were given 10 subcutaneous injections of 50 mg/kg body weight of DMAB or the corn oil vehicle at two-week intervals. In addition, cadmium was administered at doses of 0, 10, or 30 mumol/kg body weight as single intramuscular injection on the 1st day of the experiment or one day after the last injection of DMAB at week 20. Two further groups were subjected to administration of cadmium at 10 mumol/kg at week 20 and then 5 mumol/kg at week 40, or 10 mumol/kg at week 20 and then 5 mumol/kg at weeks 30, 40 and 50. At the termination, 60 weeks after the beginning of the experiment, the incidences and multiplicity of ventral prostate carcinomas in the groups given cadmium plus DMAB demonstrated a consistent tendency for increase over control values (groups receiving DMAB or cadmium alone). The numbers of carcinomas per rat and per unit area of prostate section were significantly elevated in the two groups given low doses of cadmium after cessation of DMAB administration. Cadmium alone also induced a few prostate carcinomas. The influence on development of prostate tumors did not appear to be a result of the induced severe testicular atrophy because serum testosterone levels were not affected. The results indicate that cadmium and DMAB can act synergistically to cause rat prostate carcinogenesis.

Magnitude and causes of mortality differences between married and unmarried men

STUDY OBJECTIVE

To determine the effect of marital status on mortality for men. In particular, to examine whether subgroups of unmarried men (widowed, single, and divorced/separated men) have a similar mortality to married men.

DESIGN

Cohort study.

SETTING

Whitehall civil service, London, between 1967 and 1969.

PARTICIPANTS

A total of 18,403 men aged 40-64 years with 18 years' follow up.

MEASUREMENTS AND MAIN RESULTS

Cause-specific mortality rates and risk factors at baseline were determined. Overall mortality was greater for all groups of unmarried men. Patterns of mortality were different in the subgroups of unmarried men. Widowed men had a significantly greater risk of dying from ischaemic heart disease (relative risk (RR) 1.46, 95% confidence interval (CI) 1.08, 1.97) which persisted after exclusion of deaths that occurred in the first two years. Divorced men had greater cancer mortality (RR 1.49; 95% CI 1.06, 2.10) that could not be explained simply by their greater consumption of cigarettes. The initial increased mortality for single men was no longer evident after adjustment for other risk factors, suggesting that single status in itself may not increase the risk. The risk for single men may have been underestimated, however, by over adjustment for possible intermediary factors.

CONCLUSIONS

Previous studies, which have examined total mortality only or have grouped all unmarried men, have masked interesting differences in the cause of death between subgroups of unmarried men. The extent to which the findings are explicable by psychosocial factors or the role of other environmental factors, which may also differ in relation to marital status, is unclear. Future work should not assume that all unmarried men have similar mortality risks and must examine the life course of each subgroup to advance our understanding of the possible causal role of marital status in disease aetiology.

Sexual rehabilitation after treatment for prostate cancer

Although there is little evidence that sexual behavior causes prostate cancer, men with prostate cancer often have sexual dysfunction before the cancer diagnosis is made. Each treatment for prostate cancer increases the prevalence of sexual problems. After nerve-sparing radical prostatectomy, the chance of recovering erections is better for men who are younger and in whom both neurovascular bundles can be spared. Definitions of "potency" after nerve-sparing surgery have not specified the rigidity of the erections achieved. Thus, some men classified as "potent" may wish additional sexual rehabilitation. The chance that definitive radiation therapy will cause erectile dysfunction probably has been overestimated. The prevalence rate may be closer to 25% of men with new problems compared with the 50% often cited in the literature. Men are more at risk to have erection problems after radiation therapy if the quality of erections before treatment was borderline. Hormonal therapy has an impact on the central mechanisms mediating sexual desire and arousability. Therefore, with most treatment methods, only approximately 20% of men remain sexually functional. Newer antiandrogenic drugs interfere less with sexual function, but their long-term ability to control prostate cancer is still under investigation. Sexual rehabilitation should be addressed by the primary care team. Sexual partners should be included in brief sexual counseling, even when a mechanical treatment for erectile dysfunction is prescribed.

The effect of interstitial hyperthermia on the Dunning prostate tumor model

The effect of hyperthermia was examined on the Dunning prostate tumor model in rats. Hyperthermia was created by heating self-regulating interstitial seeds with an external oscillating magnetic field. The seed alloy was comprised of 70% nickel and 30% copper. One treatment with 50C seeds for two hours did not provide significant delay in tumor growth compared to controls. However, regimens with two treatments separated by either 48 hours or one week did cause significant delay (p = 0.0013 and p = 0.0096, respectively). These results suggest that an interstitial hyperthermia seed may provide an efficacious outpatient therapy for prostate cancer. Further, interstitial hyperthermia may be readily combined with existing radiotherapy with interstitial gold coated seeds to provide additive or synergistic anti-tumor effects.

Chromosomal abnormalities and related events in prostate cancer

The amount of cytogenetic information on prostate cancer is relatively sparse when compared with that on other common adenocarcinomas. This is primarily due to frequent overgrowth in culture of the cancer cells by normal (diploid) cells. Although newly introduced techniques of in situ hybridization will undoubtedly reveal chromosome changes in a high percentage of primary and noncultured prostate cancers, such information is at present essentially limited to numeric changes, with structural changes (eg, translocations and deletions) not being readily or reliably ascertained with presently available in situ approaches. Future developments are likely to overcome these shortcomings and, thus, make possible detailed analysis of karyotypes in prostate cancer in a much higher proportion of these tumors than available up to now. The cytogenetic data on prostate cancer in the literature are reviewed in this article and, based on the frequent involvement of some chromosomes (nos. 2, 7, 8, 10, and 16) in and molecular data on prostate cancer, a suggested multistep process for the development of prostate cancer is presented. The steps in this process may not apply to all prostate cancers or in fact be the definitive ones, but the suggested scheme does indicate that a number of ordered genetic events are involved in the process of prostate cancer genesis. Epidemiologic and familial aspects of prostate cancer also have been discussed in this review as they might relate to the genetics of the disease.

The hypothesized hormonal control of mammalian sex ratio at birth--a second update

Further evidence is adduced to support the hypothesis that the sexes of mammalian (including human) offspring are partially controlled by parental hormone levels at the time of conception. The evidence relates to variation of sex ratios at birth with (1) time of insemination within the cycle of several species, (2) excision of accessory sex glands in rodents, (3) occupation of parents, (4) dominance rating of human mothers and (5) the ordinal rank of wives in polygynous marriages. Much medical research will stem from the hypothesis if it proves to be true. (a) If it were, there would be implications for the testing of causes of many diseases: and it is noted here that the sex ratios of offspring of victims of two types of cancer (prostatic cancer and non-Hodgkin's lymphoma) are consistent with the suspected causes of these diseases. (b) There are a large number of rheumatic diseases associated with the HLA markers B 27 and B 8. These markers are apparently associated respectively with high testosterone levels in men and low testosterone levels in women. If these finding should be confirmed, a causal role for this hormone seems likely in some of these diseases. It will be interesting to examine sex ratios of relatives of probands with these diseases.

The association of breast cancer and colorectal cancer in men. An analysis of surveillance, epidemiology, and end results program data

There is a known increased risk for the co-occurrence of both breast cancer and colorectal cancer in the same women, presumably as a result of either shared reproductive hormonal or environmental risk factors. Using data from the Surveillance, Epidemiology, and End Results Program of the National Cancer Institute, the authors investigated whether there is a similar relationship between breast cancer, colorectal cancer, and prostate cancer in men. The observed-expected ratio was not significantly elevated for either colorectal cancer after breast cancer or for breast cancer after colorectal cancer in men. There was an increased incidence of prostate cancer after colorectal cancer, but this relationship was not present in the opposite direction and is believed to result from detection bias. There was an increased incidence of breast and colorectal cancer in women. These results suggest that the observed breast and colorectal cancer relationship in women may be a result of shared reproductive hormonal factors.

Drug therapy of prostatic cancer

While hormonal therapy has been the usual and appropriate treatment of advanced or metastatic prostatic cancer for the past 50 years, the recent development of new therapeutic agents as medical alternatives to orchidectomy has drastically altered the options and perspectives in the treatment of this disease. Estrogens had been the only commonly used drug therapy in the United States. Newer alternatives include androgen synthesis inhibitors, a class of agents termed antiandrogens, and gonadotrophin-releasing hormone (GnRH) [luteinising hormone-releasing hormone (LHRH)] analogues, either alone or in combination. As the result of basic scientific studies and prospective clinical trials which have examined the issue of risk versus benefit, several trends have emerged. In the United States, orchidectomy is waning as the primary treatment option for metastatic prostatic cancer, while estrogen use has declined drastically; GnRH analogues are being prescribed more frequently. Furthermore, combination therapy with GnRH analogues (or orchidectomy, to a lesser extent) and the antiandrogen flutamide is gaining wider acceptance as a primary treatment option. The rationale, advantages, and real or potential disadvantages of these various treatment options are discussed.

Case-control study of screening for prostatic cancer by digital rectal examinations

Although commonly thought to be an effective method of screening for prostatic cancer, digital rectal examinations have yet to be shown by controlled study to help prevent advanced forms of this disease. 139 men with metastatic (stage D) prostatic cancer (cases) were compared with an equal number of matched men free of this condition (controls), with respect to rectal examinations recorded in the medical records up to, on average, 23 years before the cases' initial diagnosis of prostatic cancer. Cases and controls were members of a large health maintenance organisation in northern California. In the 10 years before initial diagnosis (excluding the last three months) the average number of examinations for routine screening (2.45 vs 2.52) or to evaluate intestinal or rectal symptoms (0.44 in both) were similar in cases and controls, respectively. After adjustment for racial differences, the relative risk of metastatic prostatic cancer for men with one or more screening rectal examinations compared with men with none was 0.9 with a 95% confidence interval of 0.5-1.7. Screening by routine digital rectal examination appears to have little if any effect in preventing metastatic prostatic cancer. If there is a small benefit, it will be difficult to demonstrate by conventional epidemiological study.

Patterns of care related to age of men with prostate cancer

A chart review study was done of 242 Stages A2 to D1 cancer patients to determine whether the age of patients with prostate cancer influenced their physicians' management strategies. Ten hospitals of varying size, medical-school affiliation, and patient socioeconomic status participated in this study. Patterns of prostate cancer care were examined using sets of branching logic standards in the form of criteria maps. A chart-based comorbidity index was used to control for the effect of coexisting diseases on cancer management. Regression models indicated that patient age affected the intensity of both the diagnostic evaluation and therapy, even after controlling for independent factors such as comorbid disease and individual hospital differences. Patients aged 75 years and older had significantly less intensive clinical staging workups and use of surgical and radiation therapies compared with patients aged 65 to 74 years and patients aged 50 to 64 years. In conjunction with similar results noted in studies of elderly patients with other malignancies, these results suggest that age bias is likely to be widespread. Physicians need to consider life expectancy, the ability of the patient to tolerate diagnostic procedures and therapies, and the quality of life in making treatment decisions.

Update in the management of prostate cancer

Prostate cancer remains one of the commonest malignancies in our community, and it appears that its incidence is rising because of the increasing proportion of the aged population. Improved technology, including the development of new tumour markers and tumour imaging techniques, and a gradually increasing community awareness of this disease, may allow earlier diagnosis. In turn, as the proportion of patients presenting with early stage disease increases, improved approaches to the treatment of localized cancer may thus yield increased community cure rates. The mainstay of treatment of advanced disease remains hormonal manipulation. The introduction of the LHRH agonists has provided an alternative to surgical castration, but has not resulted in an improved response rate or survival from first-line therapy. We believe that these agents do not offer a major benefit, when compared with the simple procedure of orchidectomy, notwithstanding the psychological sequelae of castration. With a median survival of less than five years after hormonal manipulation, many patients still require salvage treatment after relapse. New hormonal therapies yield objective and subjective response rates of approximately 15% and 30%, respectively, but the median survival from the time of hormonal failure remains less than one year. Cytotoxic chemotherapy has not provided a panacea, but has shown definite evidence of antitumour activity in this disease. The use of relatively non-toxic single cytotoxic drugs can provide effective palliation of symptoms in up to 40% of patients and may even prolong survival in some patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Epidemiology of prostatic cancer: a case-control study

A population-based case-control study of prostatic cancer in Alberta was undertaken to determine the risk factors associated with the disease. Cases were 382 newly diagnosed prostatic cancer patients and 625 controls, group-matched to the anticipated age distribution of the cases, chosen at random from the health insurance roster. Subjects were interviewed in their homes by using a pre-tested questionnaire including questions related to ethnic group, education, puberty, marital history, family history, residence, water supply, smoking, and diet. Factors significantly related to the risk of developing prostatic cancer included ethnic group (British high, Ukrainian low), education (elementary high, university low), age at first marriage (early high, late low), family history (high risk for those with relatives with prostatic cancer), and increased masculinity among the children of cases. The results with respect to smoking, occupation, medical history, birthplace, residence, water supply, and diet were generally negative.