When people take a certain medication for the first time, they are essentially participating in a little experiment: Medications don't always work as well as hoped, and even the best doctors can't say for sure whether a specific medication will actually help in a specific individual. Although a treatment might work straight away in some people, in others it may only work after a while or not at all. Different people also tolerate medications differently.
Researchers are trying to find out how to more accurately predict who certain medications or treatments will work in, and who they won't work in. The advantages of being able to better predict how effective a treatment will be are clear: A lot of patients would be spared ineffective treatments and unnecessary side effects.
How personal is personalized medicine?
In recent years, the old idea of individually tailored treatment has been given several new names, including personalized medicine, precision medicine, and sometimes genomic medicine.
These terms could easily suggest that treatment is actually tailored to the individual, like with custom-made dental (tooth) crowns. But most examples of personalized medicine are still about treatments for larger groups of patients. The difference is that more factors and patient characteristics are taken into account nowadays when deciding which treatment group people should be in. The scientific term for this approach is "stratification," so it is also sometimes referred to as stratified medicine.
Regardless of which term is used, they basically all mean the same thing: Before deciding whether to try out a certain treatment, a more accurate diagnosis is made. This often involves doing laboratory tests to measure the levels of certain substances in your blood, take a closer look at your cell metabolism or analyze changes in your genes. Personalized medicine is based on these biological markers, also known as "biomarkers." Many biomarkers were only discovered in the last few years.
So, nowadays, personalized medicine actually means using a specific combination of tests and treatments. Depending on the test results, a specific treatment will be recommended.
Example: Malignant melanoma
Nearly all of the organs in our body have cells in them that divide and multiply in a controlled way to replace dead cells. Normally, several safeguards built into the cell division process prevent cells from dividing uncontrollably. These safeguards don't work in cancer cells.
Some kinds of cell changes are typical for certain types of cancer. For example, some patients with malignant melanoma (skin cancer) have a change in their cancer cells known as a BRAF V600 mutation. This mutation contributes to the uncontrolled growth of the tumor. Recent years have seen the development of medications that target the BRAF V600 mutation. Before starting treatment, a sample of tissue is taken from the tumor and analyzed in a laboratory. Only those patients whose cancer cells have the BRAF V600 mutation in them then have treatment with a medication that targets the mutation.
This treatment can slow down tumor growth in people who have the mutation, at least for a few months. Full recovery cannot be expected, though. Patients who don't have this mutation don't benefit from this treatment.
The human immunodeficiency virus (HIV) multiplies in the cells of the immune system and destroys them. Without proper treatment, the immune system of most patients with an HIV infection is weakened so much that they become seriously ill. This stage of the HIV infection is called “AIDS” (acquired immunodeficiency syndrome).
The currently available medications for the treatment of HIV cannot make the infection go away again. But they can prevent immunodeficiency for decades.
One of these medications is the drug abacavir. Although this drug is effective, it causes potentially life-threatening side effects in about 5 out of 100 patients within the first few weeks of treatment. Nowadays we know that this hypersensitivity reaction only occurs in people who have a specific gene (HLA-B*5701). So before treatment with abacavir is started, a blood sample is taken first. Patients who are found to have the gene are treated with other medications.
How are the benefits of personalized medicine tested scientifically?
The pros and cons of a treatment can only be determined if certain kinds of studies are carried out. Even if lab tests and initial studies suggest that a new drug could be particularly effective in some groups of patients, solid evidence is needed in order to show that the treatment actually does what it is claimed to do. Good studies can help patients to decide whether or not to have a specific treatment.
The people who participate in these studies do so voluntarily, after being given detailed information about the study and what it will involve. To find out whether test results can predict how well a specific treatment will work, all of the participants can be tested before receiving treatment, without the test results being revealed at first. As with all good-quality studies, one half of the participants are randomly assigned to the group that receives the new treatment, and the other half are randomly assigned to the group that is given the current standard treatment.
Once the outcomes of the treatment become available, the researchers can look at the results of the tests done at the beginning of the study and check whether the patients' test results could actually predict how well the treatment worked.
"Truly" personalized medicine
The term "personalized medicine" is generally used to describe an approach that involves doing specific diagnostic tests and then choosing the most promising treatment based on the results of those tests.
But "truly" personalized medicine involves much more: Doctors really take the time to talk and listen to their patients, to ask them about their life circumstances, personal values and wishes, and take these into account. Only then can people be given enough information to understand the pros and cons of their treatment options, enabling them to play an active role in choosing a suitable treatment together with their doctor. But this is rarely what is meant by the term "personalized medicine."
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Institute for Quality and Efficiency in Health Care (IQWiG, Germany). Vemurafenib - Benefit assessment according to § 35a Social Code Book V; Dossier assessment; commission A13-34. Cologne: IQWiG. December 11, 2013.
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Mallal S, Phillips E, Carosi G, Molina JM, Workman C, Tomazic J et al. HLA-B*5701 screening for hypersensitivity to abacavir. N Engl J Med 2008; 358(6): 568-579.
Schleidgen S, Klingler C, Bertram T, Rogowski WH, Marckmann G. What is personalized medicine: sharpening a vague term based on a systematic literature review. BMC Med Ethics 2013; 14: 55.
Windeler J, Lange S. Nutzenbewertung personalisierter Interventionen: Methodische Herausforderungen und Lösungsansätze. Ethik Med 25: 173-182 (2013).
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