The Prostate Cancer Prevention Trial: Current status and lessons learned

Systematic review of electronically delivered behavioral obesity prevention interventions targeting men

Globally, obesity persists at epidemic rates. Men are underrepresented within behavior-based obesity prevention research. As men prefer individualized, self-guided interventions, electronic delivery of treatment modalities has potential to reach this population. The purpose of this study was to systematically review primary, secondary, or tertiary behavioral obesity prevention interventions that used controlled designs; targeted men; and incorporated at least one electronically delivered treatment modality explicitly designed to elicit an intervention effect. Literature searches were delimited to peer-reviewed articles; published between 2000 and 2021; in the English language; and indexed in PsycINFO, CINHAL, MEDLINE, CENTRAL, and WOS electronic databases. Interventions satisfying inclusion criteria were critiqued for methodological quality using the Jadad Scale (0 = lowest quality; 10 = highest quality). Eleven studies satisfied the inclusion criteria (n = 1748; total participants) with five reporting group-by-time intervention effects on the primary variable targeted. Jadad scale quality assessment scores ranged from 5.00 to 9.00 with a mean of 7.72. Majority of the interventions applied a randomized control trial design (n = 10). Most interventions were theory based, with eight rooted in social cognitive theory. Behavior change strategies included self-monitoring (n = 10), personalized feedback (n = 8), health counseling (n = 8), and goal setting (n = 9). Community-level theories have the potential to guide future obesity prevention interventions targeting men.

Serum Retinol and Carotenoid Concentrations and Prostate Cancer Risk: Results from the Prostate Cancer Prevention Trial

BACKGROUND

Findings from epidemiologic studies examining associations of serum retinol and carotenoids with prostate cancer risk have been inconsistent. This case-control study nested in the Prostate Cancer Prevention Trial evaluated associations of serum retinol and carotenoids with total, low-, and high-grade prostate cancer risk in a highly screened study population.

METHODS

We used logistic regression adjusting for age, family history of prostate cancer, race, body mass index, and serum cholesterol to estimate ORs and 95% confidence intervals (CI) of prostate cancer by quartiles of serum retinol and carotenoids, separately in the placebo (975 cases/1,009 frequency-matched controls) and finasteride (708 cases/743 frequency-matched controls) arms of the trial.

RESULTS

Serum retinol concentrations were associated with increased risk of total prostate cancer [OR (95% CI) comparing the highest quartile of serum retinol with the lowest: 1.30 (1.00-1.68)] and high-grade prostate cancer [OR (95% CI), 1.74 (1.14-2.68)] in the placebo arm of the trial only. Also in the placebo arm, there was a moderate positive association of α-carotene with risk of total prostate cancer [OR (95% CI), 1.32 (1.01-1.73)]. None of the other carotenoids was associated with prostate cancer risk in the placebo arm. No associations were observed for retinol and carotenoids in the finasteride arm.

CONCLUSION

In the placebo arm of this prospective study, high serum retinol and α-carotene concentrations were associated with increased risk of total and high-grade prostate cancers.

IMPACT

Men with higher levels of serum retinol and α-carotene may be at increased risk for prostate cancer.

Association between Serum Phospholipid Fatty Acids and Intraprostatic Inflammation in the Placebo Arm of the Prostate Cancer Prevention Trial

Inflammation may play an etiologic role in prostate cancer. Several dietary factors influence inflammation; studies have shown that long-chain n-3 polyunsaturated fatty acids are anti-inflammatory, whereas n-6 and trans fatty acids are proinflammatory. We evaluated whether serum phospholipid n-3, n-6, and trans fatty acids were associated with intraprostatic inflammation, separately in 191 prostate cancer cases and 247 controls from the placebo arm of the Prostate Cancer Prevention Trial (PCPT). Men without a prostate cancer diagnosis underwent prostate biopsy at trial end, and benign prostate tissue inflammation was evaluated in approximately three biopsy cores per man; this was expressed as no, some, or all cores with inflammation. In controls, serum eicosapentaenoic acid [OR of all cores with inflammation versus none (95% CI), 0.35 (0.14-0.89)] and docosahexaenoic acid [OR (95% CI), 0.42 (0.17-1.02)] were inversely associated with, whereas linoleic acid [OR (95% CI), 3.85 (1.41-10.55)] was positively associated with intraprostatic inflammation. Serum trans fatty acids were not associated with intraprostatic inflammation. No significant associations were observed in cases; however, we could not rule out a positive association with linoleic acid and an inverse association with arachidonic acid. Thus, in the PCPT, we found that serum n-3 fatty acids were inversely, n-6 fatty acids were positively, and trans fatty acids were not associated with intraprostatic inflammation in controls. Although, in theory, inflammation could mediate associations of serum fatty acids with prostate cancer risk, our findings cannot explain the epidemiologic associations observed with n-3 and n-6 fatty acids.

Future directions in the prevention of prostate cancer

The high global incidence of prostate cancer has led to a focus on chemoprevention strategies to reduce the public health impact of the disease. Early studies indicating that selenium and vitamin E might protect against prostate cancer encouraged large-scale studies that produced mixed clinical results. Next-generation prostate cancer prevention trials validated the impact of 5α-reductase inhibitors in hormone-responsive prostate cancer, and these results were confirmed in follow-up studies. Other interventions on the horizon, involving both dietary and pharmacological agents, hold some promise but require further investigation to validate their efficacy. In this Review, we discuss the clinical and preclinical evidence for dietary and pharmacological prevention of prostate cancer and give an overview of future opportunities for chemoprevention.

A Summary of the Prostate Cancer Prevention Trials With a Focus on the Role of Vitamin E

Prostate cancer is the most common noncutaneous malignancy in men. It is an excellent target for primary prevention. Vitamin E trials conducted for prevention of prostate cancer have had conflicting results with a lower incidence of prostate cancer in the ATBC trial and a higher incidence in the vitamin E arm of the SELECT trial. Most of the clinical trials with vitamin E have been limited to the alpha-tocopherol isoform alone. An increasing body of evidence suggests, however, that the gamma- and delta-isoforms of tocopherol and tocotrienols are more promising with regard to cancer prevention. This review tries to justify our assertion that the gamma- and delta-isoforms of tocopherol and tocotrienol might be superior as prostate cancer preventers.

Joint National Cancer Institute-Food and Drug Administration Workshop on Research Strategies, Study Designs, and Statistical Approaches to Biomarker Validation for Cancer Diagnosis and Detection

Cancer remains the second leading cause of death in the United States, in spite of tremendous advances made in therapeutic and diagnostic strategies. Successful cancer treatment depends on improved methods to detect cancers at early stages when they can be treated more effectively. Biomarkers for early detection of cancer enable screening of asymptomatic populations and thus play a critical role in cancer diagnosis. However, the approaches for validating biomarkers have yet to be addressed clearly. In an effort to delineate the ambiguities related to biomarker validation and related statistical considerations, the National Cancer Institute, in collaboration with the Food and Drug Administration, conducted a workshop in July 2004 entitled "Research Strategies, Study Designs, and Statistical Approaches to Biomarker Validation for Cancer Diagnosis and Detection." The main objective of this workshop was to review basic considerations underpinning the study designs, statistical methodologies, and novel approaches necessary to rapidly advance the clinical application of cancer biomarkers. The current commentary describes various aspects of statistical considerations and study designs for cancer biomarker validation discussed in this workshop.

Common genetic polymorphisms and prognosis of sporadic cancers: prostate cancer as a model

To date, most molecular epidemiological studies on gene polymorphisms in cancer have focused on the risk of development and susceptibility to cancer. However, interindividual genetic variation may contribute greatly to the treatment outcome and prognosis of cancer by affecting the interaction between cancer cells and hormones, growth factors and factors influencing the tumor microenvironment. In prostate cancer, several recent molecular epidemiological studies suggested the possibility of predicting treatment outcome and prognosis using genetic polymorphisms. Candidate genes are hormone-related, oncogenes, tumor-suppressor and cell cycle-growth control-related genes, as well as genes related to immune response, inflammatory change, neovasculization, and the extracellular matrix, genes involved in drug and xenobiotic metabolism and genes involved in DNA repair and genome stability. There remain a huge number of candidate genes whose polymorphisms may affect the progression and treatment outcome of various kinds of cancer, including that of prostate cancer.

What's new in the field of prostate cancer chemoprevention?

Chemoprevention trials for several malignancies are completed, planned, or underway. Prostate cancer is one of the most common forms of cancer and understandably has received considerable recent attention as a potential target for chemoprevention. This article examines chemoprevention trials for prostate cancer, including the Prostate Cancer Prevention Trial, Selenium and Vitamin E Cancer Prevention Trial, and cyclooxygenase inhibitors in the prevention of prostate cancer.

Prevention of Hormone-Related Cancers: Prostate Cancer

Androgens are known to play an important role in normal prostate development, benign prostatic hyperplasia, established prostate cancer, and in prostate carcinogenesis. However, despite convincing experimental and clinical evidence, the epidemiologic data correlating sex steroid levels with disease risk is inconsistent. More recent work has focused on studies of polymorphisms in germ-line DNA in an effort to develop polygenic models of prostate cancer susceptibility and prognosis. Such models have the potential to aid in the selection of men for specific chemopreventive interventions and to help determine which men with localized prostate cancer are most likely to benefit from aggressive therapy. In this review, we will provide a brief summary of androgen metabolic pathways followed by an assessment of the epidemiology literature addressing the relationship between androgens and prostate cancer. Finally, we will address the two major questions that have arisen in response to the recently published results from the Prostate Cancer Prevention Trial: Who are the best candidates for finasteride chemoprevention, and what are the clinical implications of the high prevalence of prostate cancer that was detected in men with prostate-specific antigen levels in the so-called “normal” range?

What’s new in the field of prostate cancer chemoprevention?

Chemoprevention trials for several malignancies are completed, planned, or underway. Prostate cancer is one of the most common forms of cancer and understandably has received considerable recent attention as a potential target for chemoprevention. This article examines chemoprevention trials for prostate cancer, including the Prostate Cancer Prevention Trial, Selenium and Vitamin E Cancer Prevention Trial, and cyclooxygenase inhibitors in the prevention of prostate cancer.

Prevalence and patterns of self-initiated nutritional supplementation in men at high risk of prostate cancer

OBJECTIVE

To define the prevalence and patterns of self-initiated herbal and vitamin supplementation among men at high risk of developing prostate cancer, as there is increasing public awareness of prostate cancer screening, risk-factor assessment and prevention, leading to increasing interest in the use and systematic study of nutritional therapies for prostate cancer prevention.

SUBJECTS AND METHODS

Since 1996 our institution has prospectively maintained a prostate cancer-risk registry through its Prostate Cancer Risk Assessment Program (PRAP). Eligibility includes African-American men, any man with at least one first-degree relative or two or more second-degree relatives with prostate cancer, or men who tested positively for the BRCA1 gene mutation. A 420-item self-administered questionnaire was completed and included the use of nutritional supplements and complementary therapies. We divided men into groups who used supplements to lessen their cancer risk and those who did not. The prevalence and patterns of use were evaluated and the two groups then compared for differences in demographic, socio-economic and risk-perception variables.

RESULTS

In all, 345 high-risk men were enrolled in the PRAP over a 5-year period. Data on the use of dietary or herbal supplements were available on 333 men (97%), of whom over half (170) reported taking one or more supplements to prevent prostate cancer. Supplement use was divided into eight categories, including vitamins, minerals, extracts from fruits/seeds, organic compounds, flowers/bulbs, leaves/bark, roots, or animal products. Most commonly used for self-initiated chemoprevention were vitamins (95%), minerals (28%), and fruit/seed extracts (18%). More than a quarter of men (27%) took three or more agents. Men taking proactive preventative measures were statistically more likely to be Caucasian and aged > 60 years (P < 0.05). African-Americans were less likely to self-initiate preventative steps. Men taking supplements tended to return more often for follow-up and participate in PRAP longer, while those not taking supplements tended to earn less and report less self-perceived risk.

CONCLUSIONS

A significant proportion of men at risk of developing prostate cancer initiate measures they perceive to reduce their risk. Although the chemopreventative efficacy of many of these supplements remains unsubstantiated, they are widely perceived by the public to reduce the risk of developing prostate cancer. These data provide an insight into patient perceptions and misconceptions of chemopreventative strategies, and may help to refine recruitment efforts in multi-institutional prostate cancer prevention trials.

The potential role of cyclooxygenase-2 inhibitors and 5α-reductase inhibitors in the prevention of urologic conditions

Prevention of urologic cancer is a new field for urology. It focuses attention on men and women who may not be under the regular care of physicians and are without symptoms of disease. Although risk factors (eg, smoking in bladder cancer, family history or African-American ethnicity in prostate cancer, cryptorchid testes in testis cancer, Von Hippel-Lindau disease in renal cell carcinoma) can identify individuals at a greater risk for genitourinary malignancies, most patients have no risk factors except gender and age. Thus, developing public health recommendations that will have a major impact on these diseases will be challenging. Prevention strategies will be held to a higher standard of safety than traditional cancer treatment unless populations at a high risk for disease can be identified. It will be necessary for urologists to monitor the field of disease prevention because of the high frequency of urologic malignancies and the growing elderly population in the United States. Urologists are frequently providers for and confidants of this patient population and must be able to counsel these men and women about the benefits and risks of such prevention strategies.

Short-term impact of cancer prevention and screening activities on quality of life

PURPOSE

There are few data on the short-term effects of participating in cancer prevention activities, undergoing genetic risk assessment, or having routine screening. The objective of this article is to systematically review existing research on short-term effects of prevention, genetic counseling and testing, and screening activities on quality of life.

METHODS

We conducted a MEDLINE search for original research studies that were published between January 1, 1985, and December 31, 2002, and conducted in North America or Western Europe. Data were abstracted and summarized using a standardized format.

RESULTS

We reviewed 210 publications. Most studies focused on psychological states (anxiety, depression), symptoms, or general health status. One hundred thirty-one studies used 51 previously validated noncancer instruments. Many researchers (12.6%) also added cancer-specific measures, such as perceived cancer risk or symptom indices. Only one study measured satisfaction or quality of provider-client communication. While one report examined lost workdays, no other economic consequences of short-term outcomes were evaluated. Among seven studies that assessed short-term outcomes preferences, only four specifically used time trade-off or linear rating scale methods. No study used standard gamble or willingness-to-pay methods. The overwhelming majority of research indicated that short-term effects were transient. Only two studies linked short-term effects to long-term cancer-related health behaviors such as repeat screening.

CONCLUSION

There is considerable heterogeneity in short-term outcome measurement. Clinicians need to be aware of potential for short-term, transient adverse effects. The impact of short-term experiences should to be linked to long-term health status and use of services.

Chemoprevention for pancreatic cancer

For a number of solid tumors, including pancreatic cancer, efforts aimed at disease prevention may be more successful than currently available anticancer treatments. While specific interventions are emerging to prevent breast, prostate, lung, and colorectal cancer, no trials of chemoprevention are being conducted in pancreatic cancer. Importantly, there are significant obstacles to the conduct of such research. However, preclinical and epidemiologic studies suggest that several drugs may have chemopreventive potential in pancreatic cancer. These include aspirin and other non-steroidal antiinflammatory drugs (NSAIDs), selective cyclooxygenase inhibitors, somatostatin analogs, selective estrogen receptor modulators (SERMs), and anti-androgenic agents. As the oncology community evaluates some of these agents in large chemoprevention trials for breast, colon, and prostate cancer, it may be found that pancreatic cancer prevention occurs as an unintended, but desirable consequence. Moreover, other general societal trends, such as smoking cessation and the widespread use of cholesterol-lowering agents and aspirin, could have a role in reducing the risk of pancreatic cancer, and in the future, may lead to a decrease in its incidence.

Development of a quantitative RT-PCR method to study 5alpha-reductase mRNA isozymes in rat prostate in different androgen status

BACKGROUND

The incidence of prostate cancer (PCa) and benign prostatic hypertrophy (BPH) continues to rise in the Western world. The development and growth of the prostate gland depends on androgen stimulation. Dihydrotestosterone (DHT) is the primary androgen responsible for prostate development and also for the pathogenesis of benign prostatic hyperplasia (BPH). DHT is synthesized in prostate from circulating testosterone (T) through the action of 5alpha-Reductase (5alpha-R) (EC 1.3.99.5), which occurs as two isozymes, type-1 and type-2. Both types are expressed in the prostate: type-2 isozyme is predominantly expressed in prostate and is implicated in BPH and PCa; type-1 isozyme is also increased in some prostatic adenocarcinomas. In recent years, various inhibitors of type-2 isozyme or of both type-1 and type-2 isozyme have been used in prostatic diseases.

METHODS

We present the first published measurements of mRNA levels of steroid 5alpha-R isozymes in the ventral prostate of rats of different androgen status. We used a novel method that combines the high specificity of competitive PCR with the sensitivity of laser-induced capillary electrophoresis (LIF-CE).

RESULTS

We demonstrated that T and DHT androgens control the expression of both 5alpha-R isozymes in rat prostrate.

CONCLUSIONS

This approach could be of great value for the study of prostate diseases in humans and would allow study at the transcriptional level of the effects of drugs that inhibit either or both of these isozymes.

Resveratrol--a prostate cancer chemopreventive agent?

The incidence of prostate cancer in Western countries continues to rise. Whilst opinion remains divided on the best treatment for localized disease, intervention for metastatic, hormone-independent cancer remains extremely limited. The concept of chemoprevention is gaining popularity as an effective means of reducing the burden of prostate cancer on the population, and many compounds with putative chemopreventive activity are currently under investigation. Resveratrol is a plant-derived polyphenolic compound which has a wide spectrum of biological activity. It has anti-oxidant and anti-inflammatory properties, and may induce apoptosis as well as modulate the function of the androgen receptor in prostate cancer cell lines. Further studies to evaluate the use of this compound as a chemopreventive agent in prostate cancer are warranted.

An endocrine pathway in the prostate, ERbeta, AR, 5alpha-androstane-3beta,17beta-diol, and CYP7B1, regulates prostate growth

Epithelial proliferation of the ventral prostate in rodents peaks between 2 and 4 weeks of age, and by week 8, proliferating cells are rare. We have used ERbeta(-/-) and CYP7B1(-/-) mice to investigate the role of ERbeta and one of its ligands, 5alpha-androstane-3beta,17beta-diol (3betaAdiol), in growth of the ventral prostate. Before puberty, ERbeta was found in quiescent but not in proliferating cells, and proliferating cells occurred more frequently in ventral prostates of ERbeta(-/-) mice than in wild-type littermates. Treatment with 3betaAdiol decreased proliferation in wild-type but not in ERbeta(-/-) mice. In rats, treatment with 3betaAdiol from postnatal day 2 to 28 resulted in reduction in growth of ventral prostates. The prostates of CYP7B1(-/-) mice were hypoproliferative before puberty and smaller than those of their wild-type littermates after puberty. Because CYP7B1 represents the major pathway for inactivating 3betaAdiol in the prostate, we suggest that ERbeta, 3betaAdiol, and CYP7B1 are the components of a pathway that regulates growth of the rodent ventral prostate. In this pathway, ERbeta is an antiproliferative receptor, 3betaAdiol is an ERbeta ligand, and CYP7B1 is the enzyme that regulates ERbeta function by regulating the level of 3betaAdiol.

Isoflavones for prevention of cancer, cardiovascular diseases, gynecological problems and possible immune potentiation

Japanese women show low incidence of and mortality from breast cancer, cardiovascular disease and climacteric symptoms compared to Caucasians. High soy bean intake is considered to attribute to that, but it is not clear whether soy protein itself or isoflavones (IFs) mixed in the soy protein has such effects. Presence of IFs in soy beans was varied by site, so we made IF-rich tablets from daidzein-rich soy germ (hypocotyl) for intervention studies. Our intervention study on young women by using the IF-rich tablet (20 and 40 mg/day) showed slight elongation of the menstrual cycle, but no adverse effects occurred. Intervention study on climacteric women showed improvement of bone density, hypertension and climacteric symptoms. Health effects of IFs on cancer occurrence, cardiovascular diseases, gynecological problems and possible immune potentiation are reviewed from functional aspects.