Everyone is different.
Research suggests that humans have somewhere between 99 and 99.9 percent in common with each other.
The remaining 1 percent can make a big difference when it comes to health, whether it is resistance or susceptibility to disease, or treatment.
Being different, our bodies react differently to treatment.
Variations in chemical and genetic composition mean that one person's response to a therapy will not necessarily be the same as the next.
As developments in the fields of genetics and technology advance, the conventional, one-size-fits-all approach to medicine starts to look outdated.
Instead, we are seeing a growing range of strategies that take into consideration the quirks of the individual.
This article will look at some of the strategies already available to help healthcare professionals meet individual patient needs, in the multifaceted field of personalized medicine.
Personalizing drug therapy for depression
Research suggests that around 50 percent of patients with depression do not respond to first-line antidepressants. What can explain this, and how can it be solved?
Current treatment is often a case of trial and error. A patient may take one medication after another, often for 12 weeks or more each time, while symptoms remain the same, or worsen.
A team from King's College London in the United Kingdom recently announced a blood test that can predict with accuracy and reliability whether an individual patient will respond to common antidepressants.
This, they say, "could herald a new era of personalized treatment for patients with depression."
High levels of blood inflammation have been linked to a lower response to antidepressants, so the team designed a test to distinguish levels of blood inflammation.
It evaluates the levels of two biomarkers: macrophage migration inhibitory factor (MIF) and interleukin (IL)-1β.
Results showed that none of the patients with levels of MIF and IL-1β above a certain threshold responded to conventional antidepressants, while with inflammation levels below this threshold did tend to respond. The findings indicate that patients with higher levels of inflammation should use a combination of antidepressants from the early stages to stop their condition from getting worse.
The two biomarkers affect a number of brain mechanisms involved in depression, including the birth of new brain cells, connections between them, and the death of brain cells as a result of oxidative stress, related to the processing of free radicals.
Depression can result when chemical signaling is disrupted, and the function of the brain's protective mechanisms is reduced.
"The identification of biomarkers that predict treatment response is crucial in reducing the social and economic burden of depression, and improving quality of life of patients," said Carmine Pariante, professor at King's College London.
Getting the right medication from the start would enhance the well-being of patients, and it would also save on healthcare costs, in terms of time and money.
Getting to the root of the problem
In 2012, the United States Food and Drug Administration (FDA) approved a new treatment for cystic fibrosis (CF), a serious, genetic condition that affects the respiratory and digestive systems. The drug is ivacaftor, known by the trade name of Kalydeco.
People with CF have a fault in the flow of salt and water on the surface of the lungs. It leads to a buildup of sticky mucus that can be life-threatening.
In 4 percent of patients with CF, this problem comes from a mutation in the gene G551D, which regulates the transport of salt and water in the body.
Ivacaftor can help around 1,200 people in the U.S., but more significantly, it is the first therapy to target the underlying cause of CF rather than the symptoms.
Genomic science enabled scientists to pinpoint the root of the problem, to develop a repair strategy, and to establish which patients it might benefit.
Cancer treatment is well suited to a genomic and individual approach.
In 1979, scientists discovered the most commonly mutated gene in human cancer: TP53, or p53. The BRCA1 gene mutation was discovered in 1994, and BRCA2 in 1995.
Targeted therapy for women with ovarian cancer caused by BRCA1 and BRCA2 are already in use. Targeted therapies aim to attack the tumor without harming healthy cells. The drugs work on DNA repair pathways that are blocked in women with mutations in BRCA1 and BRCA2.
In 2011, the Wall Street Journal published an infographic indicating what percentage of different cancers were likely to stem from genetic mutations that could be targeted by specific drugs. The figures ranged from 21 percent of people with cancers relating to the head or neck to 73 percent of melanoma cases.
Jen Trowbridge, researching how genomics affects cancer at the Jackson Laboratory in Bar Harbor, Maine, foresees that instead of telling a person that they have brain cancer or lung cancer, doctors will be saying, "you have cancer that's caused by this mutation, and we have a drug that targets that mutation."
Identifying genes to prevent disease before it starts
People's genetic makeup affects their future health and longevity. Genetic information can help scientists to predict what diseases people are likely to get, and how their bodies are likely to react.
In April 2016, scientists from the Scripps Translational Science Institute (STSI) found that in a group of over 1,400 healthy 80-105-year-olds, there was a "higher-than-normal presence of genetic variants offering protection from cognitive decline."
In particular, they found an absence of the coding variant for COL25A1, a gene that has been associated with the development of Alzheimer's disease.
Gene-editing techniques, such as "CRISPR," that modify DNA by "snipping" it, could prevent the onset of age-related diseases such as Alzheimer's in later years.
Women with a family history of breast cancer can undergo screening for BRCA1 and BRCA2 mutations to decide whether to take preventive action, such as a mastectomy, to minimize the risk of developing breast or ovarian cancer in future.
Recent research has suggested that women with the BRCA1 mutation should consider having children earlier, because the fault may affect the number of eggs in the ovaries.
Jen Trowbridge puts it this way: "Conventional medicine continues to treat the symptoms, but genetic scientists are now working to get right to the roots of diseases, the 'birth of a cancer,' starting from cell one."
Personalized medical devices
Advances in biotechnology also contribute to personalized medicine.
New imaging technology means that assessments of a patient's condition and needs can be ever more precise.
The data gathered can lead to tailor-made devices, and even regenerative medicine.
One example is the personalized tinnitus masker, with custom-tailored audio signals that can be configured to meet the needs of the individual patient.
Mobile health (mHealth) solutions include interconnected, wearable medical devices that feed back to the doctor a person's heart rhythms and other vital data, enabling remote monitoring, and any appropriate tweaking of treatment.
Replacement body parts
3-D printing and regenerative medicine have already provided patients with replacement body parts, including bone and a windpipe.
A CT scan assesses patient needs, computer-aided design plans the structure, and 3-D printing creates the final product. A device that is implanted surgically can then dissolve over time, as the body naturally replaces it with human tissue.
Researchers in the U.K. recently created the prototype of a 3-D-printed bone scaffold. The device would allow tissue to grow around it and new human bone to develop, as the artificial bone dissolves.
The device would match the patient's exact size and shape, and its porous nature would allow blood flow and cell growth to occur.
In 2013, physicians at the University of Michigan and Akron Children's Hospital created a bioresorbable airway splint to treat a critically ill infant. The child's airway walls were so weak that breathing or coughing could cause them to collapse. The device provided a placeholder for cells to grow naturally around it, as the body healed itself.
An FDA report describes this as "a glimpse into a future where truly individualized, anatomically specific devices may become a standard part of patient care."
Into the future
Until now, diseases have been treated with a relatively narrow range of therapies. Randomized controlled trials have been the most reliable guarantee of safety and efficacy. If the majority of people respond to a treatment in tests, it is considered successful.
But no treatment is 100 percent successful, because everyone is different.
Genome sequencing and advancing technology are shifting the perspective on healthcare, bringing tailor-made treatment further within reach.
Written by Yvette Brazier