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Precision medicine is still a relatively new term to many
people. This innovative approach to medicine tailors a patient’s treatment plan
according to their unique characteristics, including genes, lifestyle, and
environment. In the world of cancer
care, this is important since we’ve seen how cancer can be very different from
person to person, and some exciting progress has already been made.
Targeted therapies are a growing part of cancer treatment.
A newer form of cancer treatment, known as targeted therapy,
is often considered the foundation of precision medicine. Researchers have
found that changes within the genes of
cancer cells are what allow them to grow and divide uncontrollably. Just like
the name implies, targeted therapies were developed to “target” those genetic
changes and stop the cancer from progressing. Targeted therapies specifically
attack the cancer cells while leaving healthy cells unharmed, as opposed to
other treatments like chemotherapy which can damage healthy cells.
Some patients may now have genetic screenings performed on
their cancer. If a genetic change is found that has a targeted therapy
available, this may be added to their treatment plan. There are targeted therapies
available for several types of cancer, including:
-
Leukemia: Gleevac (imatinib) was the first
FDA-approved targeted therapy for chronic myelogenous leukemia in the 1990s. -
Breast cancer: Herceptin (traztuzumab) is used
for HER2-receptor positive breast cancer. -
Colorectal cancer: Drugs that block epidermal
growth factor receptor (EGFR) protein may help slow the growth of colorectal
cancer. -
Lung cancer: Like colorectal cancer, blocking
the EGFR receptor can help treat lung cancer. -
Melanoma: Almost 50% of melanomas have a genetic
mutation in the BRAF gene. Those that do can benefit form a BRAF-inhibitor
drugs.
There are not currently targeted therapies for all types of
cancer, and not all patients are eligible based on their cancer’s genetic
makeup. However, as precision medicine continues to advance, researchers
continue to seach for new genetic changes and develop targeted treatments.
Precision medicine is shifting the way cancer is treated.
For many years, cancer treatment regimens were largely based
on where the cancer originated in the body and how far the disease had
progressed. So, for example, two people with Stage IV lung cancer would often receive
the same course of treatment. Yet, just recently, the FDA approved Keytruda
(pembrolizumab) as the first cancer treatment to be used based on the cancer’s genetic
makeup, regardless of where in the body it first occurred. Only those patients
whose tumors have specific gene mutations, confirmed through medical testing,
are eligible candidates for Keytruda.
This is just the start. There are currently many other
clinical trials, called basket studies, underway to look at how cancer
treatments work against different types of cancer that share the same genetic
mutations. Researchers remain hopeful that just like Keytruda, this shift will
provide countless patients with access to more effective cancer therapies.
Precision medicine is making cancer treatment more safe and effective.
Another area of precision medicine, called pharmacogenomics,
looks at how genetics affect the way our bodies respond to medication. When
dealing with strong cancer medications, like chemotherapy, it’s critically
important to ensure the drugs are being used safely and effectively. Rather
than making desions based solely on weight or body surface area, pharmacogenetics
can provide dosing recommendations. Some examples include:
-
Patients with colon cancer may receive a genetic
test before being given a type of chemotherapy, Camptosar (ireotecan). If they are
found to have a certain genetic mutation, they may not be able to eliminate the
drug properly and would require a lower dose. -
Children with acute lymphoblastic leukemia may
be tested for a genetic variation that would affect their ability to metabolize
chemotherapy safely.
Cancer prevention may be possible with the use of precision medicine.
Finding new ways to treat cancer is great, but preventing it
from occurring in the first place is even better. Testing for the presence of
the BRCA1 or BRCA2 mutation is probably the most well-known method of using
precision medicine in this way. Patients
that test positive for the mutation can be counselled on what can be done to
lower their risk of developing breast or ovarian cancer, from receiving more
frequent cancer screenings to having preventative surgery to remove the breasts
or ovaries.
Researchers continue to collect genetic data from large
numbers of people with the eventual goal of being able to pinpoint certain
variations that lead to the development of cancer. Many researchers believe
this data is crucial to the future of cancer prevention, resulting in the
identification high-risk populations, the development of anti-cancer vaccines,
and beyond.
The
goal of precision medicine for cancer is clear—provide each patient with the
most effective treatment while reducing the risk of harm. While many advances
have already been made, it is still a growing area of medicine. If you’d like
to learn more, talk to your doctor. He or she can help you determine if you are
a good candidate.
