The drugs being tested in PROVENT are Aspirin and Vitamin D3. These drugs are not new medicines, they are used frequently by millions of people worldwide.

As with many other commonly used drugs, Aspirin and Vitamin D3 have been the subject of a great deal of research over the years, in several different areas of medicine. The results have proved interesting. It seems that both drugs may be (either alone or in combination) helpful in the fight against cancer, because they might prevent certain cancers from growing and changing.


Aspirin: 100mg orally daily (one tablet)


Aspirin: 300mg orally daily (one tablet)


Aspirin Placebo (dummy tablet): orally daily (one tablet)

Aspirin is a well-known anti-inflammatory drug, used mainly to control pain and fever. However, research has shown that Aspirin can also have anti-carcinogenic (anti-cancer) effects. In particular, it has been shown to help prevent cancers of the digestive tract. Several studies have also looked at the effect of Aspirin on prostate cancer, with many showing that it can be beneficial both in terms of incidence (the number of new cases in a population) and progression. But other studies have been less conclusive, and there are many unanswered questions.

PROVENT will look at:

  • Which types of prostate cancer may benefit from Aspirin treatment?
  • Which dose of Aspirin is most effective?
  • How long it needs to be taken for to prove effective?
  • How to balance any benefit with the risk of side effects?

Aspirin is generally a well-tolerated drug, but it can cause side effects in some people. Gastric bleeding is a particular risk, and it may also interact with other medications. Therefore, Aspirin should only be taken on a daily basis under medical supervision, and should be avoided by some people entirely.

Vitamin D3

Vitamin D3: 4,000IU/0.1mg orally daily (8 drops)


Vitamin D3 Placebo (dummy liquid): orally daily (8 drops)

Vitamin D3 is an essential Vitamin that helps the body to absorb calcium and phosphorus. The body produces most of its Vitamin D naturally when the skin is exposed to sunlight. However, many people are deficient in this vital Vitamin. Long winters with little sunlight, sunscreens, indoor lifestyles, clothing and dark skin can all limit the amount of sun that reaches us, and can result in low levels of Vitamin D3 in the body.

A certain amount of Vitamin D can be gained from food such as eggs, oily fish, and fortified dairy or cereal products, but these don’t tend to be enough to provide the amount of Vitamin D required for good health. Doctors will often prescribe a short course of replacement Vitamin D for patients found to be deficient in this Vitamin. It’s also prescribed for a variety of other conditions, such as osteoporosis and rickets.

Several studies looking at Vitamin D3 and prostate cancer have reported interesting findings. It seems that the Vitamin may decrease the risk of aggressive prostate cancer and disease progression. However, this research is limited so far, and there have also been a number of conflicting reports. PROVENT aims to find out whether Vitamin D3 can stop prostate cancer that is not high risk from developing into higher risk disease.

Vitamin D3 is extremely well tolerated. However, at higher doses it may interact with some other medications, like certain cardiac drugs and antacids, so it does require medical supervision. Vitamin D3 increases the amount of calcium in the blood, so potential PROVENT participants will be tested to check that their calcium levels are normal before they are accepted into the study.


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