President Jimmy Carter and Precision Cancer Medicine: In December 2015, former President Jimmy Carter announced that he no longer displayed any signs of cancer following his diagnosis and treatment for metastatic melanoma that had spread to his liver and brain. Carter had undergone a regimen of surgery, radiation, and targeted immunotherapy, crediting a drug called pembrolizumab (Keytruda) for playing a significant role in his apparent early remission. (The Carter Center).
For patients battling cancer, Carter’s story was inspiring: an older patient with a metastasized disease had achieved remarkable results with the aid of a promising new drug. His high-profile case put a new spotlight on a phenomenon commonly known as “precision cancer medicine”: a targeted approach to cancer treatment that’s providing hope and an expanded range of options for doctors and their patients. What is precision cancer medicine and if you or someone you love is fighting the disease, how might new advancements in targeted cancer therapy affect your options for treatment?
PRECISION CANCER MEDICINE DEFINED: DECODING THE BUZZWORD
According to UpToDate.com, precision (sometimes called “personalized”) medicine “refers to the application of patient-specific profiles, incorporating genetic and genomic data as well as clinical and environmental factors, to assess individual risks and tailor prevention and disease-management strategies” ([1] UpToDate). Put more simply: doctors are learning more about the human genome all the time, and are using that knowledge to develop new ways to treat disease. Combined with information about a patient’s lifestyle, environment, and history, doctors may then use that knowledge to decide which treatments might be most effective for each individual patient.
The somewhat broad umbrella of “precision medicine” includes (but is not limited to) oncology.
Oncologists have long sought an alternative to the “spray and pray” approach of traditional chemotherapy, which destroys healthy cells as well as malignant ones and overwhelms the body with a battery of harmful side-effects (such as hair loss, anemia, and even an increased risk of secondary cancers). Certain modern techniques now permit doctors to be more precise and less invasive in their approach, isolating and destroying cancer cells with reduced toxicity and fewer side-effects for the patient. Examples of these techniques include targeted radiation therapies (like stereotatctic radio surgery) ([2] UpToDate), and targeted pharmaceuticals (such as the pembrolizumab that doctors chose to treat Jimmy Carter).
GENOMICS: FROM SCREENING TO TREATMENT
So, how do doctors choose which precision treatments to use? You may have heard your doctor talk about something called genomic testing: that is, the analysis of an individual’s DNA to identify certain traits that may place him or her at increased risk for cancer or other diseases, and that may determine the particular type of cancer a person has. By referencing your genetic data prior to treatment, doctors may be able to make more informed decisions about which course of therapy to pursue. In theory, this strategy should help minimize side-effects, keep costs down, and save valuable time that might be lost through a trial-and-error approach to treatment. (National Foundation for Cancer Research)
Even if you don’t currently have cancer, you may wish to utilize genetic profiling to gain a better picture of your overall health and facilitate the prevention, diagnoses, and treatment of certain cancers in the future. For example, a woman with a family history of breast or ovarian cancer may choose to utilize genetic profiling in order to determine whether she carries a mutation in the BRCA1 and BRCA2 genes, which is associated with an increased risk for the disease. If testing reveals that she does carry a mutated copy of the gene, she may choose to undergo more frequent screening measures (such as regular mammograms) in a effort to detect cancer early; she may also elect to undergo a prophylactic mastectomy or oophorectomy to decrease her risk of developing the disease. If she does ultimately develop breast or ovarian cancer, her genetic status may help her doctors determine a more specific (and ideally, more effective) course of treatment: for example, her oncologist may choose to prescribe a PARP inhibitor after an initial regimen of chemotherapy, which research suggests may be particularly effective in women with BRCA-mutated ovarian cancers.
A better understanding of how your particular type of cancer functions on a molecular level may guide your doctor in choosing certain drug treatments over others. In the case of Jimmy Carter, doctors utilized a type of pharmaceutical called an immune checkpoint inhibitor to treat his melanoma in conjunction with surgery and focused radiation. Immune checkpoint inhibitors help activate the human body’s natural immune responses to attack abnormal cancer cells but leave normal, healthy cells unharmed. In addition to melanoma of the skin, this type of immunotherapy has shown promise in treating non-small cell lung cancer, kidney cancer, bladder cancer, head and neck cancers, and Hodgkin lymphoma ([1] American Cancer Society).
PRECISION CANCER MEDICINE: WHAT’S THE CATCH?
It’s important to remember that we still have much to learn about cancer. Doctors are still learning about the benefits and limitations of genomic medicine, and our understanding of how precision cancer medicine might compliment more traditional therapies is still unfolding.
As some doctors were quick to note, it may be premature to label any one factor as the “most significant” element in former President Carter’s remission: in addition to targeted immunotherapy, traditional surgery and focused radiation also played important roles in his treatment (MedPage Today). Others postulated that early detection may have improved his prognosis, giving him an overall advantage no matter what treatment strategy his doctors chose (CNN). And above all, the longterm efficacy of Carter’s treatment has yet to be determined: after all, cancer may still recur in the future even after a patient goes into remission and shows no signs of the disease ([2] American Cancer Society).
In addition, the new age of precision cancer medicine and genomic profiling has brought with it the inevitable array of enterprising corporate entities (some more reputable than others), all claiming to offer genetic testing services to directly to the public. These direct-to-consumer testing (or DTC) services have come under increased scrutiny by the FDA, and their efficacy at predicting genetic risk for disease appears unreliable ([1] UpToDate). If you decide to pursue DTC genetic testing, always get a second opinion from your doctor before using the results to embark on a new course of treatment.
IN CONCLUSION
As we enter this new era of medical understanding and discovery, we must remain hopeful but cautious. While modern targeted therapies provide more choices and greater agency for doctors and patients alike, we should be careful not to mislabel the advent of precision cancer medicine as an all-encompassing “miracle cure.” That said, our understanding of the human genome continues to expand by the day, as does our arsenal of promising resources for detecting and treating various forms of cancer – and that’s exciting news! For people like former President Carter, precision medicine may indeed pave the way for a longer, healthier life.
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REFERENCES
The Carter Center: Statement From Former President Jimmy Carter. December 5, 2015.
https://www.cartercenter.org/news/pr/carter-center-statement-120615.html
[1] UpToDate: Personalized Medicine. Benjamin A Raby, MD, MPH. Topic last updated: April 16, 2016.
[2] UpToDate: Radiation therapy in the management of melanoma. Arnand Mahadevan, MD. Topic last updated: January 16, 2017.
National Foundation for Cancer Research: Cancer Genomics.
[1] American Cancer Society: Immune Checkpoint Inhibitors to Treat Cancer. Last Revised: March 23, 2017.
MedPage Today: Most Experts Not Surprised By Carter’s Status. Charles Bankhead, December 8, 2015.
http://www.medpagetoday.com/HematologyOncology/SkinCancer/55076
CNN: Jimmy Carter is ‘cancer free’: Miracle or just science? Sandee LaMotte, December 7, 2015
http://www.cnn.com/2015/12/06/health/jimmy-carter-cancer-doctor-interview/index.html
[2] American Cancer Society: Understanding Recurrance.
