Scientists identify new prostate cancer risk factor

Cancer Research UK

Cancer Research UK scientists have found that the greater the levels of a protein called Insulin-like Growth Factor-1 (IGF-1), the greater the risk of (prostate cancer, according to a study published in the Annals of Internal Medicine today (Monday).

An international team of researchers, led by the University of Oxford, collected and analysed data from 12 previous independent studies on the relationship between blood concentrations of suspected prostate cancer risk factors, and subsequent onset of the disease. Previously, some but not all studies have suggested a link between IGF-1 levels and increased risk of developing the disease.

IGF-I levels are influenced by lifestyle factors such as diet, so the results of this rigorous analysis could help scientists find ways to reduce men's risk of developing prostate cancer by tailoring advice to men at high risk.

The scientists looked at the data of blood samples of 3,700 men with prostate cancer and 5,200 men without the disease. Blood samples were taken on average when the men were 62 years of age, five years before they were diagnosed with prostate cancer. The research found that men with higher levels of IGF-1 were more likely to go on to develop prostate cancer than those with lower levels of the protein.

Lead author Dr Andrew Roddam, a Cancer Research UK epidemiologist at the University of Oxford, said: “There is a need to identify risk factors for prostate cancer, especially those which can be targeted by therapy and/or lifestyle changes. Now we know this factor is associated with the disease we can start to examine how diet and lifestyle factors can affect its levels and whether changes could reduce a man's risk.

“But it's important to point out that there is no evidence to suggest that measurement of IGF-1 levels could be used to develop new prostate screening methods. Other studies have shown that existing methods of detecting prostate cancer are not improved by also measuring IGF levels.”

Prostate cancer is the most common cancer in men in the UK accounting for a quarter of all new cases of cancer diagnosed in men. More than 34,000 men in the UK are diagnosed with prostate cancer each year. The disease is the second most common cause of cancer death in UK men, after lung cancer and causes around 10,000 deaths a year.

Dr Lesley Walker, Cancer Research UK's director of cancer information, said: “While there are established risk factors associated with prostate cancer of age, family and ethnicity there are no clear data on modifiable risk factors. Research like this is vital to further the work on prevention and treatment of the disease. The findings are also likely to be of interest to scientists who are looking at developing drugs to prevent prostate cancer. “Cancer Research UK will continue investing in research to identify the causes and ways to prevent prostate cancer as well as ways to treat it."

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Notes to Editor

Andrew W Roddam et al. Insulin-like Growth Factors, their binding proteins and prostate cancer risk: A collaborative analysis of individual data from twelve prospective studies (2008). Annals of Internal Medicine. 2008;149:461 - 471

Principal investigators of prospective studies that have published data on circulating concentrations of sex hormones, IGF or insulin-like growth factor binding proteins (IGFBP) and prostate cancer risk were invited to join this collaborative study.

Most of the studies were population based with the exception of one based on health plan members, two which recruited male health professionals and one which was a cardiovascular disease monitoring study.

Data collected on individual participants included age, weight, smoking status, alcohol consumption, marital status, socio-economic status, race, blood concentrations of IGF, IGBPs, sex hormones and prostate specific antigen. Information gathered on prostate cancer cases included date of diagnosis, stage and grade of the disease.

Risk of developing prostate cancer

Due to the nature of the data collected for this collaboration, it is not possible to calculate an individual risk of prostate cancer. However, the results are important as they help us understand about the causes of prostate cancer.

IGF-1 and relevance to all cancer

Other studies have investigated the connection between circulating IGF-I levels and the development of other common cancers. Although there is some evidence that IGF-1 levels may be related to an increased risk of breast cancer, results from individual studies are somewhat conflicting. There is also some evidence that IGF-I may be linked with colorectal cancer, but the data is more sparse than for breast cancer. For other cancers the data is limited.About prostate cancer

Prostate cancer is rare in men under 50. The risk increases if there is a first-degree relative (father or brother) who was diagnosed with prostate cancer at a young age. Prostate cancer is most common in men of African descent, and least common in men of Asian origin.

Some evidence suggests that a diet high in dairy products may increase the risk.

Symptoms include, having to rush to the toilet to pass urine, passing urine more often and/or at night, difficulty starting the flow of urine, starting and stopping whilst passing urine, a feeling of not having emptied the bladder fully, dribbling of urine, blood in urine or semen and pain in the back, hips or pelvis.

There is a blood test available to detect prostate cancer. It measures prostate-specific antigen (PSA), a chemical produced by the prostate. PSA levels are usually raised when a man has the disease. However the use of a PSA test is not currently recommended for screening in the UK as its potential benefits are still unclear and are being evaluated in clinical trials. It’s important for men who would like a PSA test to discuss all the options with their doctor.

Treatment will depend on the stage of the cancer and the age and general health of the patient. If the disease is at an early stage, does not cause symptoms or discomfort, and does not require aggressive treatment, doctors may suggest delaying treatment until the cancer shows signs of progressing further. Treatment can involve surgery, radiotherapy, hormone therapy and less often, chemotherapy which is of limited use in treating prostate cancer but is used if the cancer has spread.

University of Oxford

Oxford University's Medical Sciences Division is one of the largest biomedical research centres in Europe. It represents almost one-third of Oxford University’s income and expenditure, and two-thirds of its external research income. Oxford’s world-renowned global health programme is a leader in the fight against infectious diseases (such as malaria, HIV/AIDS, tuberculosis and avian flu) and other prevalent diseases (such as cancer, stroke, heart disease and diabetes). Key to its success is a long-standing network of dedicated Wellcome Trust-funded research units in Asia (Thailand, Laos and Vietnam) and Kenya, and work at the MRC Unit in The Gambia. Long-term studies of patients around the world are supported by basic science at Oxford and have led to many exciting developments, including potential vaccines for tuberculosis, malaria and HIV, which are in clinical trials.

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