What Is Precision Cancer Medicine?
Precision medicine is the tailoring of medical treatment to the individual characteristics of each patient and his or her disease, but what does this really mean?
Physicians have always treated patients based on specific characteristics of their disease. For example, the treatment for strep throat is drastically different than the treatment for congestive heart failure or type 2 diabetes.
Even among patients with cancer, those with lung cancer have long received a different course of treatment to those with leukemia.
So what is new? Why all the talk about precision medicine and precision cancer medicine?
The bottom line is that research conducted in the past two decades powered an explosion in our understanding of the biology of cancer, in particular cancer genomics, and in our ability to translate this ever increasing knowledge for the benefit of patients.
One thing that we have learned is that not all cancers of a given type are characterized by the same genetic alteration, or mutation, and that this provides an avenue for precision cancer medicine. For example, we know that about 5 percent of non-small cell lung cancers – the most common form of lung cancer – are driven by alterations in a gene called anaplastic lymphoma receptor tyrosine kinase (ALK). Many patients with ALK-positive non–small cell lung cancer, like James "Rocky" Lagno, benefit from drugs that block ALK, such as crizotinib (Xalkori) and ceritinib (Zykadia).
Moreover, we have learned that we can expand the use of ALK-targeted precision medicines because small numbers of patients with other types of cancer are also characterized by ALK mutations.
One patient benefiting in this way is 10-year-old Zach Witt, who was diagnosed with anaplastic large cell lymphoma at 5 years of age. When his cancer returned during standard chemotherapy, his parents were told that genetic testing had revealed that his cancer was driven by ALK mutations and that he might benefit from crizotinib treatment. He received the precision medicine as part of a clinical trial and remains cancer-free to this day.
Through the precision medicine approach, the treatment of each patient can be focused on drugs most likely to benefit him or her, sparing the patient the cost and potential harmful side effects from drugs that are unlikely to be beneficial. For example, drugs targeted to the HER2 protein are offered only to the 20 percent of breast cancer patients who have disease that tests positive for high levels of HER2.
Currently, genomics is the main factor influencing precision medicine in oncology. However, other factors, including a patient’s disease presentation, gender, lifestyle, and exposures to potential cancer-causing agents like cigarette smoke could be considered in precision medicine. Moreover, as research teaches us more about both normal human biology and cancer biology, other factors are likely to influence precision medicine decisions in the future.
As our ability to analyze and integrate patient characteristics increases, we can expect faster and broader implementation of precision medicine across the spectrum of cancer care, from cancer prevention and early detection to treatment of late-stage disease.
We can also expect greater use of precision medicine in the treatment of other diseases; thus far, oncology has been leading precision medicine efforts largely because of our immense knowledge of the role of genetic mutations in the development and progression of cancer.