Personalized medicine

Personalized medicine, also called precision medicine, is health care tailored specifically to an individual based on information from the person's genetic makeup. A broader definition includes medical care customized to the person in any way, such as altering the dosage of a medication based on a person's tolerance for it. However, those who specialize in developing personalized medical techniques prefer the definition that specifies the aspect of customization based on genetics. Personalized medicine is a relatively new field of medicine. It originated in the latter half of the twentieth century and attracted greater interest after the human genome was completely mapped in 2003. Personalized medicine shows great promise for preventing, anticipating, and curing many conditions. Still, some believe that the interest in personalized medicine is greater than the medical industry's ability to accommodate it.

Background

Although the idea of customizing medical care for patients had its origins in the 1960s, the concept of "personalized medicine" did not appear in print until 1999, when several journal articles and other sources began to use the term. However, it was still difficult to achieve anything remotely like personalized medicine—also called genomic medicine or precision medicine—until the human genome was mapped in 2003.

For most of the history of medicine, physicians have adhered to what have been called "standards of care." A condition was identified, its symptoms and causes were listed and described, and physicians tried different ways to treat it. Once they found a method that worked with reasonable consistency for many patients, this method became the standard of care. For example, a person with breast cancer might have a mastectomy, or breast removal surgery, and be started on a chemotherapy drug known to work on breast cancer. Physicians might treat every patient with breast cancer the same way.

These methods began to change when the human genome was sequenced, or mapped, in the early years of the twenty-first century. For the first time, it was possible to know which genes and which parts of human DNA were responsible for different aspects of a person's physical makeup. DNA, or deoxyribonucleic acid, is a substance in each human cell that determines the cell's appearance and function. In effect, it codes every aspect of the human body.

Scientists discovered that while about 99 percent of DNA in a human body is the same as the DNA in every other human body, about 1 percent is unique to each person. This 1 percent is what accounts for individual differences in appearance and various traits in people. Scientists also came to realize that DNA controlled not only visible traits such as height and skin color but also differences in how people's bodies responded to diseases and to the medications used to treat them. In time, researchers discovered that at least some conditions responded to medications and treatments in different ways. The discovery opened a new avenue for treatment: personalizing the treatment to account for these differences. These customized treatments became known as genomic medicine, or personalized medicine. Personalized medicine allows physicians to choose medications and treatments for conditions based on the patient's genes.

Overview

The concept of personalized medicine is in its infancy, with physicians just beginning to understand how to tailor treatments for different conditions based on genetics. One of the first ways personalized medicine was able to be used was in predicting the likelihood that a person might develop a condition based on genetics. For instance, researchers determined that people with mutations, or alterations, to the genes known as BRCA1 and BRCA2 were more likely to get breast cancer. They began testing for these genes in people with a family history of breast cancer. Knowing whether they carried the mutation allowed patients to make decisions, such as having more frequent testing or even having preemptive breast removal surgery, to prevent cancer.

Knowing the genetic makeup of tumors has helped physicians make decisions about the best types of treatment for patients who already have cancer, too. Researchers have begun to determine that tumors with certain mutations or other identifiable factors do or do not respond to different types of chemotherapy. As a result, physicians are able to choose the treatments that are most likely to work against a particular patient's cancer.

The biggest advances in treatment resulting from genetic testing and personalized medicine have been in cancer treatment, the treatment of cystic fibrosis, and the treatment of human immunodeficiency virus (HIV). However, other conditions, such as celiac disease, are benefiting from it as well. Physicians are able to use the results of genetic testing to determine the best dose of some medications and to predict whether people will have side effects from the treatment.

Although personalized medicine appears to have great potential, it does have some drawbacks. Genetic testing is costly and is not always covered by insurance. Results may be misread, as most physicians are not trained geneticists. New information about genes is discovered nearly every day, which makes it difficult for family doctors and physicians in specialties outside genetics to keep up.

Experts also urge caution in considering the increasing array of "home DNA" tests that have become available. They question the accuracy of some of these tests and note that the results that are returned can contain generic wording that may lead some people to attempt to self-treat conditions that require professional attention.

Some critics note that personalized medicine does not yet live up to the hype about its possibilities. In some cases, researchers have discovered information about the genetic makeup of a condition without knowing how to use that information to improve treatments. Supporters of personalized medicine urge patience and note that it is a new form of medical care and will improve in time.

One developing area in personalized medicine is the effort to diversify the pool of genetic data available to researchers. By ensuring that genetic data more accurately reflects human diversity in terms of genetic makeup, environment, lifestyle, family history, and other factors, researchers can better understand causes and treatments of disease, and develop treatments that are more effective for people of all backgrounds. In 2015, the National Institutes of Health's Precision Medicine Initiative Working Group established a framework for the federally funded All of Us Research Program. Given that existing genetic research had focused on people of European ancestry or who would self-identify as White, All of Us set out to reduce racial disparities in genetic research by collecting genetic sequences from one million people of diverse backgrounds for its database. By February 2024, the program started releasing genetic sequences from 245,000 volunteers along with researchers' analyses of the data. Researchers found over one billion genetic points of variation in the volunteers' genomes, including 275 million variants that had not been previously detected. Some experts voiced concerns that the program overemphasized the importance of genetics on health and was unintentionally perpetuating scientific racism, the false idea that race is a biological category rather than a social construct. The program countered such concerns, arguing that although genetics do not explain all health issues, genetic variations do differ by population, and having a diverse genetic database is the key to delivering effective personalized medicine. The program also noted that it collected detailed data about each volunteer's lifestyle, environment, and behaviors, in addition to their genetic sequences.

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