By Malaika Mathias, Fall 2019.

Everybody is different. We hear it all the time. Each of our bodies respond differently to the food we eat, changes in weather, and even to medical treatments. So why do we all continue to take the same medicines, if we are all different in our responses to them? 

Precision medicine is an emerging sector of medical treatments that tailor each drug to the individual patient, based on their specific needs and genetic makeup. Currently, it is being studied for use in spinal muscular atrophy, Huntington’s disease, and primarily, for various types of cancers. While approximately 40% of people are diagnosed with cancer in their lifetime, not all cancers are caused by the same mutation. Precision medicine relies on the patient’s genetic changes to create a custom-fit medicine that is targeted to the very mutation that occurred, along with taking into account the patient’s drug sensitivities and other concerns. In the case of cancer, precision therapy is a type of immunotherapy: a treatment that utilizes the body’s immune system to attack the cancer itself, rather than having the drug attack the tumor directly. This method of targeted therapy has proved far more successful than current treatments like chemotherapy and radiation, as it kills the cancer cells successfully without compromising the health of non-tumor cells. 

The need to improve the current state of immunotherapy by introducing precision medicine in cancer treatment can be summed up in three ways. Firstly, current treatments are simply not up to the mark: in many cases, they end up being incredibly destructive and leave patients weakened from receiving far more treatments than required, instead of the single targeted treatment that would work best for them, with maximized results and reduced side effects. 

Secondly, only 12.48% of patients respond to current immunotherapies, and it is even more disheartening that only 43.63% are eligible for this type of therapy in the first place. This is because the immunotherapy market is still developing, and several cancers still lack their own targeted therapy. Further, several patients actually do experience side-effects with immunotherapy, as current treatments still do not prevent the occasional damage of healthy cells. Determining who will respond to treatment without taking into account one’s genetics is a huge challenge, one that personalized medicine strives to eliminate by administering a drug specific to the patient.  

Finally, the current state of cancer treatment administers therapies based on the type of tumor. This causes a problem when cancers occur in areas outside clearly defined body parts, or worse, several of them, making it hard to categorize what type of cancer it is. For example, if one were to have a tumor growing on the back of their hand: would we categorize this as a cancer of the hand or of the skin? This challenge is solved using a patient’s genetics: the genome is a universal biological language and can be used as a definite measure of what went wrong. Thus, looking at the tumor’s mutation is far more conclusive than trying to eyeball the type of cancer. 

Now that we have identified the benefits of precision medicine, let’s take a closer look at how the process is carried out. Initially, the patient’s DNA is extracted – both from healthy somatic cells as well as from tumor cells – and genetic changes are identified using DNA sequencing and genomic testing techniques. Additionally, the cells undergo a variety of other tests including a tumor biopsy and tumor profiling. It is helpful at this point to note that it is not the entire 20500 genes in the genome that are consistently studied; the process is streamlined to look only at SNPs (single nucleotide polymorphisms) – or the sections of the genome with greatest genetic variability among individuals. Next, a treatment is identified to suit the patient based on their mutation and other personal factors such as family history and overall health. Usually, this is done by administering a drug with an immune body that is complementary to the mutated protein. This means that the ligand on the mutated protein may be identified by an immune cell (like T-cells for example), which may then be able to attack it. The molecular structure of the drug thus stimulates an immune pathway to target the tumor. In personalized medicine, individual factors like age, sex, and location are taken into account. All this considered, the personalized targeted treatment is created and administered, and the patient is hopefully responsive to it. Artificial intelligence and large databases allow for efficient evaluation at this point in the procedure.  

Sounds too good to be true? It is perhaps too early to conclusively determine the prevalence of precision medicine in the medical society forthcoming. While investigating teams seem to be convinced by this novel way of treating patients, there are drawbacks to be considered.

Cost associated with precision treatments seems to be one of the biggest concerns people have when considering its applicability. While the genetic tests involved are covered by insurance, the actual treatment itself remains expensive. However, with precision medicine streamlining treatment, in the end less money would be spent on inefficient side treatments that are less effective. For example, many cancer patients end up paying for a multitude of treatments of varying efficiencies during their prognosis; here, only one powerful treatment is needed. 

Another concern is that since every person receives a different formula of the treatment, tailored to their unique genetics, the clinical testing of each individual drug must be limited. Hence, it is argued that we cannot accurately gauge the side effects, strength, and effectiveness of every individual treatment as it hasn’t been widely tested on large groups of people. While this is a strong argument against precision medicine, it is for this very reason that the concept exists: to limit side effects, the person’s genetics are studied, and strength is similarly tailored to what is needed based on the mutation and body’s response. Effectiveness, likewise, is also unpredictable with any other drug, as we never know how it will react in one’s body; here, in fact, unpredictability is minimized by targeting the drug to the ways in which the patient is likely to respond. 

Finally, since genetic information is extracted and stored, data privacy concerns exist. However, with appropriate measures, the benefits brought by precision therapy may be more significant than these concerns. 

Today, the state of personalized treatment in cancer is still developing. One doctor, Vinay Prasad, has recognized that only less than 10% of patients are currently eligible for this genome-based treatment, as biomarkers have not been identified and selected for a multitude of cancers so far. The situation today involves therapies targeting a specific mutation that is common to several with the same cancer. For example, in non-small cell lung cancer (NSCLC), the drug Crizotinib is used to target the anaplastic lymphoma kinase (ALK) gene that is present in this type of tumor. Future direction may ensure that each drug further becomes more specific in its customizability to each individual person’s mutations.  

Overall, the ideal of precision medicine appears encouraging in the sphere of cancer medicine, with potential to significantly increase response rates and lower side effects while maximizing the effectiveness of the treatment. It will be a matter of time before either these drugs become either commonplace – and every patient ideally has access to them – or obsolete. For now, it is up to research to choose which path they take.

1. “Has the Promise of Precision Medicine Been Oversold?” Has the Promise of Precision Medicine Been Oversold? – The ASCO Post. Accessed November 2019. https://ascopost.com/issues/october-25-2018/has-the-promise-of-precision-medicine-been-oversold/.
2. Krzyszczyk, Paulina, Alison Acevedo, Erika J Davidoff, Lauren M Timmins, Ileana Marrero-Berrios, Misaal Patel, Corina White, et al. “The Growing Role of Precision and Personalized Medicine for Cancer Treatment.” Technology. U.S. National Library of Medicine, 2018. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6352312/. 
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