In some ways, cancer treatment has always been personalized. When you are diagnosed with cancer, a healthcare team recommends a treatment plan just for you. The plan is based on the type of cancer and what they know about it, including the stage. The plan is also based on your personal situation and what you want. Two women with the same stage of breast cancer may have the same treatment plans or they may have different treatment plans because one woman chooses to have mastectomy and no radiation therapy while the other woman chooses breast-conserving surgery and radiation therapy. Some men with prostate cancer may choose to have the prostate removed by surgery while others may choose radiation therapy as their treatment.
Personalized medicine, which is also called precision medicine, takes the personal to an entirely new and different level.
What is personalized medicine?
Personalized medicine uses information about a person to prevent, diagnose and treat disease. It helps doctors choose treatments based on a person’s genes or other features of the cancer the person has. There is still a lot to learn, but doctors hope that personalized medicine will mean that people with cancer have better outcomes from their treatment with fewer side effects and that they will stay cancer-free for longer after treatment.
Over the last 5 to 10 years, researchers have learned a lot about the changes inside a cancerous tumour that cause it to grow and spread. They have studied the genetic and molecular makeup in many people with cancer to learn more about how a person’s genes and the proteins they make can increase the risk of cancer. Knowing what has caused a cancer to develop can give doctors clues about how to treat it.
When doctors find and study genes in people with cancer it can lead to new treatments that target gene mutations that cause cancer. Finding gene mutations can help them diagnose cancer as well as develop and choose treatments that are most likely to work for that person’s cancer and cause fewer side effects. Studying genes in a person with cancer can also help us learn if others who carry the same gene mutation may have a higher than normal risk of developing a certain type of cancer. This helps researchers to study ways to prevent cancer or find cancer early in people with gene mutations.
Personalized medicine can be used to:
- predict how likely you are to develop cancer
- select who may benefit from earlier screening or tests to find cancer early
- match a person to treatments that are more likely to work while causing fewer side effects
- plan and monitor treatment
- develop new treatments
- help people with cancer make treatment decisions that are right for them
Personalizing cancer treatment
No two cancers are the same. No two people are the same. And people with the same type of cancer don’t respond to a treatment in exactly the same way. Personalized medicine allows doctors to choose a treatment plan, such as targeted therapy, based on the genes, proteins or other molecules inside the tumour (called the genetic or molecular profile). It’s a different approach to treatment – not based as much on the type of cancer and where it is in the body, but more about choosing treatment that targets the specific features of that cancer. Personalizing treatment in this way may lessen harmful side effects and make it more likely that the treatment will work.
It starts with testing for genetic changes
When cells or tissue are removed after a biopsy or surgery, they are sometimes tested to look for certain genes or proteins that are known to be linked to cancer. Doctors can also look for extra copies or mutations of certain genes or proteins. People who have certain gene mutations, gene changes or abnormal proteins may benefit from targeted therapy.
Liquid biopsies, which allow doctors to look at cancer cells, pieces of tumour DNA (called circulating tumour DNA) and other substances released by the tumour, may reveal even more about the genetics of the tumour and someday help guide treatment decisions.
Gene mutations can also help doctors predict which cancers are most likely to come back (recur) and which people are most likely to benefit from treatment. Researchers can use gene-based tests like microarray analysis, gene expression profiling and DNA sequencing. Microarray analysis allows researchers to look at many genes together to see which ones are turned on and which ones are turned off. Analyzing many genes at the same time to see which are turned on and which are turned off is called gene expression profiling. DNA sequencing allows researchers to look at the DNA to find changes such as gene mutations.
Oncotype DX is a test that looks at 21 genes in some women with breast cancer. It uses gene expression profiling to find out which breast cancers are likely to spread (metastasize) or come back (recur). The results of the test can help identify which women are most likely to benefit from adding chemotherapy to their treatment.
MammaPrint is a test that looks at 70 different genes. It helps doctors find out the likelihood of recurrence and response to chemotherapy in women with early-stage breast cancer.
Different cancers, same treatment
Personalizing treatment in this way means that people who have different types of cancer but whose cancers have the same mutated genes or abnormal proteins may have the same treatment. The treatments that are used to target these genes or proteins are targeted therapies, but some are also types of immunotherapy. Some examples of how personalized medicine is used to help choose treatment include:
- Lung cancers that have gene mutations in the epidermal growth factor receptor (EGFR) can be treated with EGFR inhibitors such as gefitinib (Iressa), afatinib (Giotrif) or erlotinib (Tarceva).
- About half of melanoma skin cancers have a gene mutation in the BRAF gene. These cancers can be treated with BRAF inhibitors such as vemurafenib (Zelboraf) or dabrafenib (Tafinlar).
- About one-quarter of women with breast cancer have a mutated ERBB2 (HER2) gene, which causes the cancer to make extra HER2 protein. These cancers can be treated with trastuzumab (Herceptin), a drug that attaches to extra HER2 proteins and can help stop the growth of cancer. People with stomach cancer who have a mutated HER2 gene may also be treated with trastuzumab.
Many people with cancer will still be treated with surgery, radiation therapy or chemotherapy. But personalized medicine allows doctors to add newer treatments that target mutated genes or abnormal proteins to help cure the cancer and prevent it from coming back.
Preventing cancer with personalized medicine
Personalized medicine isn’t just about treating disease. It may help us better understand how we can prevent cancer. As we learn more about the link between certain gene changes and cancer, we can also help predict which people may be more likely to develop cancer over their lifetime. So if you have a certain genetic change, your doctor may run tests on a regular basis to help find cancer early or suggest you make certain lifestyle changes to help lower your risk of cancer. We know that not smoking, reducing how much alcohol you drink, healthy eating and being physically active help lower cancer risk. These changes may be even more important for some people.
Personalized medicine is still under study
Many of the drugs used in personalized medicine are still under study in clinical trials. Most people with cancer won’t be treated with personalized medicine unless there is a drug approved for use in Canada to treat their type of cancer. To receive the drug you also have to meet certain criteria such as having advanced cancer or have tried other treatments that are no longer working. You can talk to your doctor to see if treatment with personalized medicine is an option for you.
New ways to design clinical trials
Personalized medicine research has taken a different approach to the design of clinical trials. Basket clinical trials test one drug that targets a mutated protein or gene in people with any type of cancer that tests positive for the mutation. Umbrella trials test several targeted therapy drugs in a group of people with different gene mutations but the same type of cancer.
Progress in personalized medicine
Progress has been made in several key areas in personalized medicine.
- More specific types of cancers are being divided into subtypes based on a gene mutation or abnormal protein. Many new targeted therapy drugs available inside and some outside of clinical trials target these gene mutations or abnormal proteins.
- Clinical trials using microarray analysis and gene expression profiling help researchers study and analyze many genes to quickly find gene mutations in several types of cancer.
- Researchers are developing new gene-based tests that may help doctors find out whether or not a certain treatment or drug will work in a specific person with cancer.
Challenges in personalized medicine
There are still many challenges in personalized medicine.
It’s a slow process. Research takes a long time, and it’s often many years before a new test or treatment is available outside of a clinical trial.
There are lots of privacy issues. Making progress in personalized medicine depends on people with cancer donating samples of tissue for research purposes. There are many laws to protect people’s privacy and many rules and regulations about using human tissue for cancer research. Of course people who donate their tissue must be protected and researchers must use tissues appropriately. But this can slow the research process as well.
Education and awareness need to improve. Many people with cancer don’t know about personalized medicine. They need to be informed – about the importance of the research, about how their privacy is protected and about how to find clinical trials.
It requires a lot of cooperation and coordination. Making progress in personalized medicine depends on researchers from different hospitals, universities and institutions working together and sharing information.
A lot of data is collected but what does it all mean? Researchers studying the molecular makeup of cancer collect a huge amount of data during the research process. This is often called big data. As researchers collect data to answer one question in a study, they often gather extra information that could help answer many other questions that aren’t part of that study. But if researchers can figure out effective ways to store, share and study this extra data, it could help answer research questions in the future.
There are drawbacks of genetic testing. Some of the genetic testing for directed therapy may turn up a genetic mutation that may or may not represent a hereditary cancer syndrome. This can cause a lot of anxiety and implicates all family members and not just the person being tested.
The basic biological unit of heredity passed from parents to a child. Genes are pieces of DNA and determine a particular characteristic of an individual.
Treatment that uses drugs or other substances to target specific molecules (usually proteins) involved in cancer cell growth while limiting harm to normal cells.
The molecules inside the cell that program genetic information. DNA determines the structure, function and behaviour of a cell.
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