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Why is it important to know which genes are present?

Some genes or gene changes can have an effect on a person’s care or treatment. For example, some abnormal genes can:

• Make a person more likely to develop a certain cancer.
• Mean a person’s prognosis (outlook) is better or worse than someone with the same cancer who doesn’t have that gene change.
• Help predict whether a person’s cancer is more (or less) likely to respond well to a certain treatment.

How is precision medicine used for people with cancer?

In precision cancer medicine, doctors use information from biopsies and other tests to put together a plan of care that will likely be the most effective for a person’s situation.

For people with cancer, this means looking at how changes in certain genes or proteins in a person’s cancer cells might affect their care and treatment options. But precision medicine can be used in other ways, too. It can help to:

• Identify people who might be at high risk for cancer, and help them lower their risk
• Find certain cancers early
• Diagnose a specific type of cancer correctly
• Choose which treatments and methods are most likely to work
• Evaluate how well a treatment is working

Which cancers can precision medicine be used for?

Some of the more common cancers where precision medicine is being used to help with treatment decisions include:

• Colorectal cancer
• Breast cancer
• Lung cancer
• Certain types of leukemia
• Certain types of lymphoma
• Melanoma skin cancer
• Esophagus cancer
• Stomach cancer
• Ovarian cancer
• Thyroid cancer

People with these cancers are usually tested for certain gene or protein changes when they are diagnosed, or shortly after. Some cancers might also be tested for changes if they keep growing during treatment, or if they come back.

Precision medicine for diagnosing and treating cancer

Diagnosing cancer

Some cancers might be tested for certain gene changes (or for proteins made because of these gene changes) that can help make a more accurate diagnosis. This testing can provide information about the cancer, including how it grows and spreads. These tests can go by many names, including:

• Biomarker testing
• Tumor testing, tumor genetic testing, tumor marker testing, or tumor subtyping
• Genomic testing, genomic profiling, or genome sequencing
• Molecular testing or molecular profiling
• Somatic testing
• Next generation sequencing

Testing is often done on a sample of the tumor (from a biopsy or surgery) if possible, but it might also be done using a sample of blood, saliva, or other body fluids.

Planning treatment

The cancer treatments most often used in precision medicine are:

• Targeted therapy (treatment designed to attack a specific target on cancer cells)
• Immunotherapy (medicines used to help the body’s immune system attack the cancer)

When planning which treatments to use, the goal is to give treatments that are most likely to be effective, while avoiding ones that might not work as well.

Two types of precision medicine tests can help with this: biomarker testing and pharmacogenomic testing.

Biomarker testing

Biomarker testing checks the cancer cells for certain gene or protein changes that can how a cancer response to certain treatments. This is often what people mean when they refer to precision medicine. Even if two people have the same type of cancer, their tumor cells could have different gene changes that affect their treatment their options.

Pharmacogenomic testing

While biomarker testing looks at gene changes in the tumor itself, pharmacogenomic testing looks at a person’s inherited DNA. This testing helps predict how well a drug will work and whether someone is at a higher risk for serious side effects by looking at how a person's body breaks down, absorbs, and uses treatment.

Cancer treatment delivery

As research on how best to use precision medicine in cancer care continues, several exciting findings have been noted. For example, smart drug delivery systems are being studied as a way to give treatment by precisely controlling how much treatment is given at a time and how often it is given.

Some smart drug delivery systems being studied are combined with wearable sensors or trackers to help control the release of a treatment based on signals from a person’s body. As the wearable sensor tracks biomedical data from a person, feedback from the sensor is sent to the drug delivery system. The drug delivery system can then adjust doses and the timing of doses based on the biomedical feedback. This means the medicine can be more specifically targeted to the affected area or cells. Many experts believe this approach can help reduce side effects and improve the treatment’s effectiveness.

Despite having great promise, these drug delivery systems have limitations related to safety and overall benefits. Much more research is needed before these are widely available and used.

Benefits of precision medicine in cancer care

Before personalized medicine, people with the same type of cancer usually got the same standard treatment. Over time, doctors noticed the treatments worked better for some people than others. Then, researchers began finding genetic differences in people and their cancers. These differences help to explain why some cancers respond differently to the same treatment in different people.

While precision or personalized medicine is useful in many people with cancer, it’s not always helpful for everyone with cancer. Sometimes the standard treatment is best for a type and stage of cancer. But your doctor may personalize treatment based on testing that’s done. Personalized medicine may also be part of a clinical trial.

Questions to ask if you have cancer

If treatment options for your type of cancer depend on certain gene or protein changes, your cancer will likely be tested for them. Here are some questions you might want to ask your doctor:

• Do I have a type of cancer that should have biomarker, molecular, or pharmacogenomic testing done on it?
• Have you done any of this testing on my cancer? What information will the tests help you find out?
• Will the results of this testing mean I will need more tests?
• How is my information kept private?
• How much will the tests cost? Will my insurance cover them?
• Will these tests help us choose which treatments are best for me?
• If testing shows a specific treatment might be best for me, how much would this treatment cost? Will my insurance cover it?

You can learn more about what questions to ask in Understanding Your Options and Making Treatment Decisions.

Precision medicine to determine cancer risk

Sometimes precision medicine is used for people who are at higher risk for developing certain cancers because of a family history. For example, a person might realize cancer runs in their family, or their doctor might notice a pattern of cancer in their family. In these cases, the person might meet with a certified genetic counselor and consider having genetic testing.

Genetic testing can show if they have an inherited gene change that puts them at higher risk for certain types of cancer. If so, the doctor might recommend screening and other tests (often at a younger age than usual) to help find cancer early, or they might prescribe medicines or suggest healthy habits that could help lower the person's cancer risk.

Questions to ask about cancer risk

If you don't have cancer, but are concerned about your cancer risk because of your family history or some other reason, here are some questions to ask your doctor:

• Do you think my family history puts me at higher risk for cancer?
• Should I get genetic counseling and testing?
• How do I find a certified genetic counselor?
• What will happen if I decide to get genetic testing? What will happen if I decide not to?
• How much does genetic counseling and testing cost? Will my insurance cover it?
• How is my information kept private?
• What might you learn about my cancer risk from genetic testing?
• How will the results affect my care?
• Will the results lead to more medical tests?
• How might the results affect my family? Would my family members need to get genetic testing?

You can learn more in Understanding Genetic Testing for Cancer.

Limitations of precision medicine in cancer

The main limitation of precision medicine is that it’s not yet available for every type of cancer. However, a great deal of research is being done in this area. Researchers are trying to fill those gaps, both in lab studies and in clinical trials. This may mean that in the future, treatments will be customized to the specific gene and protein changes in each person’s cancer.

Other limitations include:

• The many words and terms that can be used to describe precision medicine are not consistently used the same way by doctors and other health professionals.
• In some places, access to the latest precision medicine approaches might be limited. And many times, there are delays in testing that can affect treatment decisions. In some cases, precision medicine may be available only through a clinical trial.
• If a doctor or health care team doesn’t have experience or current knowledge about biomarker testing, it might not always be used in the best way. Its results might not be adequate, or the results might not be used to make the best decisions about a person’s health.
• The costs of biomarker testing and the medicines that might be recommended as a result of testing can sometimes be a concern.
• Sometimes biopsy samples are small, with limited amounts of tumor cells. This can limit how much testing can be done on the tumor.

Possible ethical concerns with precision medicine

• There may be unequal access to testing and treatment. Because precision medicine isn’t available everywhere or for all cancers, it could lead to health disparities based on where people live, the type of cancer they have, and whether their insurance covers it.
• Understanding treatment options can be more difficult. Precision medicine can be complex. If people don’t fully understand the risks, benefits, and limitations of their treatment options, they may be unable to give truly informed consent to treatment.
• There may be concerns about privacy and discrimination. Like all genetic testing, precision medicine can raise questions about how personal and genetic information is used, stored, and kept private and confidential. Laws offer some protections against discrimination based on genetic testing, but concerns remain.

If you're wondering if precision medicine is an option, ask your cancer care team. They can tell you what testing has already been done for your cancer, and if there are other tests that might be helpful. They can also explain the benefits, risks, and alternatives to precision medicine, based on your situation. It’s important to ask questions, take time to understand the details of your cancer, and make an informed decision about what's right for you.

Costs of precision medicine in cancer care

Experts believe precision medicine might help lower health care costs in some ways. For example, it can help guide doctors in choosing treatments that are likely to work best. This means a patient might avoid getting (and having to pay for) treatments that aren't likely to work well, along with unnecessary side effects (and the possible costs that might go along with them).

But precision medicine might also increase some costs of cancer care in these ways:

• Tests for gene and protein changes can be expensive, especially if many are being tested for, and insurance might not cover all testing costs.
• For people who are found to be at higher risk for cancer because testing shows they have an inherited gene mutation, there might be increased costs from getting recommended screening tests and other preventive care. (On the other hand, they are doing what's needed to help lower their risk of cancer or to find it early, when it's often easier to treat, which might help them avoid higher costs in the in the future.)
• For people whose best treatment option is a specific targeted therapy or immunotherapy treatment, based on a cancer's gene or protein changes, the treatment itself might be expensive.