Chemoprevention: Preventing cancer with drugs

There is no pill that generally protects against cancer. However, researchers are gaining a better understanding of how individual types of cancer develop. The aim of so-called chemoprevention is to use medication to prevent one or more steps in the development of cancer.

Such drugs are approved in the USA, but only to prevent certain types of cancer, such as breast cancer. We summarize the importance of drugs to prevent cancer in Germany.

Breast cancer: tamoxifen, anastrozole and co.

Studies show that certain medications can reduce the risk of breast cancer, especially in women who are at higher risk of developing breast cancer. These include tamoxifen, raloxifene and so-called aromatase inhibitors such as anastrozole and exemestane. In Germany, however, these drugs for the prevention of breast cancer have not yet been approved.

Why are the drugs not approved in Germany? Further studies are still missing for approval in Europe or Germany. In addition, according to experts, the possible risks can be greater than the benefits.

What are possible risks? Drugs used to prevent breast cancer can have serious side effects:

• For example, women can experience symptoms similar to menopause.
• Tamoxifen and raloxifene also put women at greater risk of blood clots and uterine cancer.
• Medications like anastrozole can cause joint and muscle pain. They also increase the risk of bone loss (osteoporosis): the drugs make the bones more porous and can break more easily.

State of research:

• The drugs do reduce the risk of breast cancer. So far, however, it has not been proven that this increases the life expectancy of women.
• According to studies, the drugs can only prevent a certain form of breast cancer: Experts refer to this form as hormone-sensitive, estrogen receptor-positive breast cancer.
• Researchers are still investigating whether the drugs are just as effective in preventing cancer at lower doses, but whether side effects can be reduced as a result.

Recommendation of the Gynecological Oncology Working Group (AGO): According to the AGO, those who have an above-average risk of breast cancer could have an advantage through chemopreventive drugs. In addition to the personal risk of breast cancer, the benefit of such drugs depends on other factors, such as how old a woman is and her personal risk of developing side effects such as blood clots. The experts at AGO recommend these women to carefully weigh all the benefits and risks with their doctor before taking any such medication.

Colon cancer: acetylsalicylic acid (ASA), celecoxib and sulindac

In Germany, the active ingredients acetylsalicylic acid (ASA), celecoxib and sulindac are not approved for the prevention of colon cancer.

Why are the drugs not approved in Germany? Further studies with long-term data are necessary for the drug to be approved. According to experts, there are still a few unanswered questions.

Status of research on acetylsalicylic acid (also known as Aspirin® or ASA for short) – The results of the high-quality long-term CAPP2 study support the assumption that Aspirin® can reduce the risk of colorectal cancer for people with what is known as Lynch syndrome – the most common cause of hereditary colorectal cancer. However, it is still unclear whether people without an increased risk of colon cancer also benefit from Aspirin® for colon cancer prevention. Although side effects were rare in studies, they can also be serious, such as severe bleeding in the gastrointestinal tract.

• The subject of research is whether ASA is really suitable for preventing colon cancer – in healthy people as well as in people with an increased risk of colon cancer. Because: In order to prevent cancer, one would have to take ASA in comparatively high doses for many years. The risk of side effects is correspondingly high.

State of research on celecoxib – In people with familial adenomatous polyposis (FAP), benign colon cancer precursors, so-called polyps, initially develop. This puts them at a very high risk of developing colon cancer, because untreated polyps in these affected individuals usually degenerate into cancer. Studies have shown that celecoxib reduces the number of colon polyps in people with FAP. However, it is unclear whether celecoxib actually reduces the risk of developing colorectal cancer. At the same time, celecoxib can cause side effects on the cardiovascular system.

State of research on sulindac – Studies have shown sulindac to reduce the number and size of polyps in people with FAP, but not to prevent them from forming again. Again, it is unclear whether the drug lowers the risk of developing colorectal cancer itself. This also applies to a combination with the drug eflornithine (Flynpovi™). Therefore, the European Medicines Agency rejected the approval of such a combination therapy in 2021.

Recommendation from professionals

Do not take Aspirin® or any other chemopreventive medication on your own. Please always consult your doctor beforehand.

Recommendation of the professional societies: Certain people can, in consultation with their doctor, take medication to prevent colon cancer – after they have carefully weighed up the risks and benefits together in advance. This includes some people with hereditary colon cancers, such as familial adenomatous polyposis (FAP) or Lynch syndrome.

Prostate Cancer: Statins, Finasteride and Dutasteride

In Germany, statins (cholesterol-lowering drugs), finasteride and dutasteride are not approved for the prevention of prostate cancer. Professional societies also do not recommend taking medication to prevent prostate cancer.

Why are the drugs not approved in Germany? On the one hand, this is due to the possible side effects, some of which are serious. On the other hand, it is also due to the fact that the drugs mainly reduce the risk of prostate cancer in the early stages. This is usually easily treatable. For this reason, experts do not consider the benefits of chemopreventive drugs to be sufficient in relation to the possible risks.

State of research on finasteride and dutasteride – These two active ingredients have been shown to reduce the risk of developing prostate cancer. But they also have side effects that can affect men: these include erectile dysfunction (erectile dysfunction). Men may also lose sex drive (libido) or their breasts may enlarge (gynecomastia).

State of research on statins – There is early evidence that statins may reduce the risk of prostate cancer. However, further high-quality studies are needed to confirm this assumption. Very rarely, statins can also cause serious side effects.

Still part of research: metformin and warfarin

Researchers are constantly finding new indications for drugs that could be used to prevent cancer in the future. These include:

• Metformin – This is a drug that non-insulin-dependent diabetics with type 2 diabetes take. There are indications from studies that these people in particular are less likely to develop cancer and that taking metformin can also improve the prognosis of cancer patients with type 2 diabetes.
• Warfarin – There are studies that indicate a reduced risk of lung cancer, prostate cancer and breast cancer. However, other studies cannot confirm this benefit.

Important to know: Research on these drugs is still in its infancy. This means that there is still a lack of long-term data and other high-quality studies. It is therefore not yet possible to conclusively assess whether they really help to prevent certain types of cancer.

Chemoprevention: Always weigh the benefits and risks

In chemoprevention, healthy people take drugs that can also have side effects. Therefore, the treating physicians must always carefully weigh up the benefits and the possible risks together with the patient beforehand.

Do you have questions about cancer chemoprevention? We are here for you.

This is how you reach the doctors of the Cancer Information Service: