Research into causes and prevention of prostate cancer

Researchers are always trying to find out more about what causes certain types of cancer. The UK Genetic Prostate Cancer Study is collecting blood and tissue samples from people with prostate cancer. These samples will be studied, along with information about how well people respond to treatment, to find out what they can tell us about the causes of prostate cancer.

The Prostate ICGC Project is also looking at changes in the genes of prostate cancer cells to learn more about the disease and how to treat it. The SEARCH study is looking at the genes of 32,000 people with various cancers, including prostate cancer.

The Birmingham Prostate Cancer Association Study (BiPAS) is looking at lifestyle and genetic factors that may increase the risk of prostate cancer. They hope to find out what effects diet, physical activity, sun exposure, and different types of job have on the risk of prostate cancer. The researchers also want to find out about particular genes that may increase the risk of developing prostate cancer. This study may also give more information about whether the PSA test is helpful in regular testing for prostate cancer. The study has closed and we are waiting for the results.

Research into preventing cancer using drugs or diet is called chemoprevention. In the past 10 years there has been a lot of interest in the prevention of prostate cancer. This is because prostate cancer is such a slow growing cancer and may be much easier to stop or slow down than many other types of faster growing cancers. Research into chemoprevention of prostate cancer includes

• The EPIC study
• Fat in the diet
• Lycopenes in tomatoes
• Soy
• Selenium and Vitamin E
• Finasteride (Proscar)
• Dutasteride
• Green Tea

The EPIC study

Cancer Research UK is supporting the UK arm of a major piece of European research called EPIC. This is the largest ever study investigating possible links between diet and cancer. Half a million people are taking part and will keep a record of everything they eat and drink. The researchers will keep in touch with them for years to see who gets cancer and who doesn't. Then they will be able to see if any patterns emerge from the diets of people who get cancer. Prostate cancer is one of the cancers included in the EPIC study.

Fat in the diet

Countries that have a low fat and high vegetable intake in their diet have lower rates of prostate cancer. When men from a low risk country move to the USA (where prostate cancer rates are high), and start eating a western diet, their rates of prostate cancer increase dramatically. But it is not certain whether this is due to fat intake. Studies are ongoing throughout the world to find out the exact effect of fat, and the type of fat, on prostate cancer risk.

The EPIC study will look into the diets of men who go on to develop prostate cancer and may add to the knowledge of the role of fat in prostate cancer. A big advantage of the EPIC study is that the people taking part keep a detailed diary of what they have eaten. So the study is more accurate than other diet studies where people are asked to look back at what they regularly eat.

Lycopenes in tomatoes

Lycopenes are chemicals found in tomatoes that may help to prevent prostate cancer. Lycopenes are antioxidants and so may help to stop cell damage in the same way as the antioxidant vitamins. All forms of tomatoes, including ketchup, contain lycopenes although the body may absorb lycopenes better if the tomatoes are processed or cooked. Some studies looking into lycopenes and prostate cancer have shown a reduction in prostate cancer. 

Some doctors believe that the evidence about lycopene is promising enough to encourage men to increase the amount of tomatoes in their diet. The ProDiet study is trying to find out if it would be possible to increase the amount of lycopene and green tea in the diet in men who are at risk of prostate cancer. The study is also looking at whether the increase would show up in blood tests.

We don't know exactly how lycopenes work. Scientists throughout the world are trying to develop compounds that are similar to lycopenes, which might be used as dietary supplements in the future. 

Soy

Countries that have a high intake of soy in their diet tend to have much lower rates of prostate cancer (and other types of cancers) compared to countries where soy intake is fairly low. The protection against cancer may come from phyto oestrogens in soy. Phyto oestrogens are chemicals found in plant foods (phyto means plant). They are similar to the female sex hormone oestrogen. 

There are different types of phyto oestrogens. Some are found in soya bean products. Others are found in the fibre of whole grains, fruit, vegetables and flax seed. Milk may also contain phyto oestrogens, but this depends on what the cows have been eating.

Men who eat a diet high in phyto oestrogens may have a lower risk of prostate cancer. In some studies, eating phyto oestrogens regularly over several weeks reduced oestrogen levels. Scientists think the active ingredients in soya are isoflavonoids and are investigating these, particularly one called genistein. Isoflavonoids can mimic oestrogen and may delay the growth of prostate cancer. This plant oestrogen is weaker than the oestrogen produced by our bodies. We need more research results before we know how important soy is in preventing prostate cancer and other types of cancers.

Selenium and Vitamin E

Antioxidant vitamins and minerals may help to prevent cancer when included in a healthy, balanced diet. In theory, antioxidants help prevent body cells from being damaged by oxygen particles called free radicals. The damage can lead to the cells becoming cancerous.

Vitamin E and the mineral selenium are two antioxidants that some doctors thought might help prevent prostate cancer. An international trial called SELECT tried to see if this could be proved. This trial has now been closed, because early results showed that neither selenium nor vitamin E, taken alone or together, helped to prevent prostate cancer. A Canadian trial looked into whether selenium, vitamin E and soy together could prevent early changes in the prostate gland changing into an invasive cancer. They found it did not prevent it. 

Finasteride (Proscar)

Another chemopreventative agent is a hormone drug called finasteride. Finasteride is already used to treat benign prostatic hyperplasia (BPH) and has been tested in clinical trials to see if it can prevent prostate cancer. It is well known that prostate cancer responds to the hormone testosterone. Finasteride helps stop the hormone testosterone changing into its active form (dihydrotestosterone – DHT). So the levels of active DHT are lowered in the prostate.

One very large phase 3 clinical trial using finasteride in the USA recently published some results. This trial is called the Prostate Cancer Prevention Trial (PCPT). They found that finasteride did seem to be able to lower the risk of prostate cancer. But men taking it had side effects, including difficulty getting an erection and a lower sex drive. Although the overall incidence of prostate cancer was lower, quickly growing, high grade prostate cancer was more common in the finasteride group.

Dutasteride

Dutasteride is a similar drug to finasteride. It is also a treatment for benign prostate hyperplasia. In 2010 the results of a large international trial called REDUCE were published. The trial was for men at increased risk of developing prostate cancer. The results showed that dutasteride reduced the risk of developing prostate cancer by about 20% over the 4 years that the men were followed up. The side effects included a lower sex drive and difficulty getting an erection. 

Green tea

Asia has much lower rates of prostate cancer than other parts of the world. Some scientists believe that this may be due to the high intake of green tea throughout Asian countries. Laboratory studies have shown that extracts from green tea can stop cancer cells from growing. Some research has looked into the possible role of green tea in preventing cancer in people, but it mostly hasn't found any links. We need much stronger evidence to prove that green tea helps to prevent cancer in humans. 

The ProDiet study is trying to find out if it would be possible to increase the amount of lycopene and green tea in men's diets who are at risk of prostate cancer. And it also wants to whether the increase would show up in blood tests.

Researchers are looking for genes that could increase the risk of cancer. Some genes have been identified that seem to increase prostate cancer risk.

Cancer Research UK scientists in London and Leeds discovered PTEN. This is an important gene involved in prostate cancer. This gene is being studied to find out how it works and how it affects prostate cancer. This work may lead to new treatments for prostate cancer in the future. 

Another gene, discovered in the USA, is called MSR1. This was found to run in some families who had a history of prostate cancer. It may be important in increasing risk of this disease. 

Researchers in the UK have also discovered a gene called E2F3 which appears to be overactive in high grade prostate cancer. This may help doctors to decide which men need treatment for prostate cancer and which men may only need active monitoring.

Families that carry the breast cancer genes BRCA1 and BRCA2 also have an increased risk of prostate cancer. The IMPACT trial in the UK is looking at screening men for prostate cancer who have an increased risk because of the BRCA1 or BRCA2 gene. 

The PROFILE study aims to find out more about family history and risk of prostate cancer. It hopes to possibly identify other faulty genes that might increase the risk of prostate cancer. You can find out more about these trials on our searchable clinical trials database. Choose 'prostate' from the dropdown list of cancer types.

In future it may be possible to carry out genetic tests for prostate cancer risk in the same way that it is becoming possible for breast cancer. Men with a higher than average risk may have tests more often, or from an earlier age. Or we may be able to develop a drug to prevent prostate cancer developing in this risk group.

There is research into different and more accurate tests to help diagnose prostate cancer. There is information here about

• PSA testing
• MCM5 protein
• PCA3 testing
• BiopSave blood test
• Testing citrate levels
• A new type of scan

PSA testing

At the moment, there is no single, effective screening test for early prostate cancer in healthy men. The use of the PSA blood test as part of a screening programme is still under discussion in the UK. 

The ProtecT study (Prostate testing for cancer Treatment) is looking at treatments for men with early prostate cancer diagnosed with a PSA test. This study initially aimed only to find out which of three treatment options is best – active monitoring, radical radiotherapy or total prostatectomy. Cancer Research UK is now funding an extension to this study to help find out more about the effectiveness of screening men for prostate cancer using the PSA test.

The researchers in the ProtecT study will look at men who are not screened for prostate cancer using the PSA test. They will follow these men and find out how many of them get prostate cancer, how it is treated and if their disease progresses. They can then compare these men to those screened in the main ProtecT trial. The trial has now closed and it will be a few years before we know the results. 

A part of the ProtecT trial also looked at the emotional effects of screening for prostate cancer on the men involved.

MCM5 protein

Researchers have discovered a group of proteins that are needed for cells to divide. These proteins are called MCM proteins. MCM proteins are found at high levels in dividing cells, and could be used to distinguish cancer cells from normal cells. The MCM5 protein is now being used to develop tests to diagnose different types of cancers. 

Detecting high levels of MCM5 in the urine may help to diagnose early stage bladder cancer. Although the main focus of research so far has been on bladder cancer, it seems that the test might be able to diagnose prostate cancer. But more studies are needed before we know this for sure.

PCA3 testing

PCA3 is short for Prostate CAncer gene 3. Prostate cells have PCA3 genes that make the cell produce a small amount of a particular protein. Prostate cancer cells make much more of this protein than normal cells. When the level of PCA3 protein is high, it gets into the urine. 

Researchers have been checking whether they can use a urine test for PCA3 protein to diagnose prostate cancer. We don't yet know how useful this test will be, and you can't have it on the NHS. But so far, trial results have been promising, and it may be used more often in the future. There is information about PCA3 testing in the prostate cancer questions and answers section.

BiopSave blood test

A Newcastle study is looking at a new blood test called BiopSave to see if it helps diagnose prostate cancer. All men taking part have the blood test and a prostate biopsy. The aim of the study is to see if the BiopSave test can predict what the result of a prostate biopsy will be. If the test can do this, it may lead to fewer men needing a biopsy in the future.

Testing citrate levels

One study is looking at testing fluid from the prostate gland to detect cancer. It is a small pilot study in Middlesborough. Doctors measure levels of a substance called citrate in the fluid using light energy. Citrate forms as part of normal body processes. Doctors want to find out if a change in the levels of citrate could be used in the future to detect prostate cancer and monitor its growth.

A new type of scan

There is a trial looking at whether DB4 can give better scan pictures. Scientists have developed a compound called DB4 (Demobesin-4), which they combine with a mildly radioactive liquid called Technetium 99 to create 99mTc DB4. They hope that this substance will show up prostate cancer more clearly on a scan. This would then help doctors to see better whether the cancer has spread outside the prostate. It would also allow doctors to know more about which treatment is most appropriate for each man.

There is information about these trials on our clinical trials database. Pick 'prostate' from the dropdown list of cancer types.

UK Prostate Link can direct you to more information about research in the field of prostate cancer.