Prostate Cancer
Case-Control Study in Shanghai
A population-based multidisciplinary case-control study was conducted in Shanghai, China to investigate the reasons for the extremely low risk of prostate cancer in China and evaluate factors that might explain the recent increase in incidence in this low-risk population. The study included 237 cancer cases, 206 patients with benign prostatic hyperplasia, and 471 healthy controls randomly selected from the population. Results to date suggest that higher levels of education, a high waist-to-hip ratio (an indicator of central obesity), and a higher intake of total calories, red meat, and animal fat and protein are associated with an increased risk, while higher consumption of allium vegetables, peppers, and mushrooms is associated with reduced risk. In addition, a shorter repeat length of CAG in the androgen receptor gene and higher serum levels of insulin and insulin-like growth factor-1 (IGF- 1) are associated with an increased risk. Several genetic polymorphisms found revealed no association with disease. Other genetic, hormonal, and micronutrient factors are also being examined using serum and genomic DNA extracted from buffy coat samples. More information, Ann Hsing.
Ghana Prostate Cancer Study
The ongoing Ghana study is designed to assess the burden of prostate cancer in Ghana in order to evaluate how the impact of prostate cancer among West Africans compares to that among African-Americans, whose reported incidence rates are among the highest in the world. West Africans and African-Americans share genetic ancestry but have very different lifestyles and environmental exposures. This study has two components: a clinical survey to estimate the incidence of clinical prostate cancer in Accra and a population screening survey to estimate the prevalence of prostate cancer in the male Accra population. The clinical component of the study includes the collection of clinical and pathological data for the more than 500 prostate cancer cases diagnosed over the last five years. The population component of the study seeks to screen 1,000 healthy men, using serum prostate specific antigen (PSA) testing and digital rectal examination, followed by biopsy confirmation as required. Interviews will be conducted to elicit information on demographics, diet, smoking, alcohol consumption, body size, medical history, health care utilization, and urinary symptoms. The collected blood samples will be used for PSA testing and for measurements of genetic, hormonal, and nutritional markers. More information, Ann Hsing.
Case-Control Study within the PLCO Cohort
We are evaluating the role of obesity, insulin resistance, and chronic inflammation in a nested case-control study of 1,400 cases and 1,400 controls within the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. Our ongoing study includes both a serum-based component to evaluate metabolic markers associated with insulin resistance and a genetic component to assess susceptibility in genes involved in the insulin signaling and chronic inflammation pathways. The large sample size of the study permits investigation of relatively small effects of biochemical markers and genetic determinants of prostate cancer. It also provides a rare opportunity to clarify whether those who are "metabolically obese" (men who are insulin resistant but do not have the obesity phenotype) have an increased risk of prostate cancer. More information, Ann Hsing.
NCI-ACS Collaborative Study
NCI investigators are collaborating with scientists from the American Cancer Society (ACS) to investigate the role of insulin resistance and chronic inflammation in prostate cancer in a nested case-control study of 1,209 prostate cancer cases and an equal number of controls selected from the ACS's Cancer Prevention Study (CPS)-II LifeLink Cohort. The ongoing collaborative study will evaluate the relationships of polymorphisms of a number of key genes involved in the insulin signaling and chronic inflammation pathways with prostate cancer risk. The insulin signaling and chronic inflammation hypotheses are novel. The insulin signaling hypothesis is an extension of our earlier work on obesity and insulin resistance. The chronic inflammation hypothesis is also closely linked to mechanisms involved in obesity and insulin resistance; it is likely to add further support to the insulin resistance hypothesis as well as provide supporting evidence linking sexually transmitted diseases and oxidative stress, two emerging hypotheses, to prostate cancer. More information, Ann Hsing.
Case-Control Study within the Washington County CLUE Cohort Study
The insulin-like growth factors (IGFs) and their binding proteins (IGFBPs) appear to play an important role in the development of prostate cancer. In collaboration with investigators at the Johns Hopkins School of Public Health, we are conducting a pilot study of IGFs, IGFBPs, and prostate cancer risk in the Washington County Serum Bank, a prospective cohort study. In 1974, over 8,000 male residents of Washington County, Maryland, donated a blood sample and completed a health questionnaire. Using the stored serum samples from 30 men who developed prostate cancer during the 25 years of follow-up and 60 men who have remained prostate cancer-free, investigators are assessing whether IGF levels in 1974 predict subsequent risk of prostate cancer. More information, James Lacey.
Prostate Cancer Risk Following Benign Prostatic Hyperplasia in Sweden and Denmark
DCEG investigators are examining population-based record linkage data from Sweden and Denmark to evaluate the risk of prostate and bladder cancer following diagnosis of benign prostatic hyperplasia (BPH). With nationwide records systems encompassing both hospital discharge diagnoses and cancer registries in these two countries, we have identified 86,626 Swedish BPH patients diagnosed during 1964-1983 and 86,683 Danish BPH patients diagnosed during 1977-1993 and are following them over time through medical records for cancer incidence and mortality. More information, Ann Hsing.
Methodologic Study of Tissue Hormones
We are carrying out a multi-racial methodologic study in the U.S. and China to investigate whether serum levels of hormones reflect intraprostatic androgenicity. A total of 600 subjects, including African Americans, Caucasians, Asian Americans, and Chinese men living in China, diagnosed with prostate cancer, benign prostatic hyperplasia, or bladder cancer undergoing prostatectomy will be recruited for tissue and blood collection. Hormone levels in prostatic tissue will be measured and compared with serum levels and polymorphisms of hormone-related genes. Levels of androgen receptor and its associated proteins in prostate tissue will be measured directly. In addition, factors such as age, smoking, and body size that might alter serum-tissue correlations will be examined. Possible racial variation in the serum-tissue correlations will also be assessed. This study is the first of its kind to investigate androgenicity in target tissue directly and will help guide future epidemiologic studies on prostate cancer. More information, Ann Hsing.
