Imatinib changed the standard of care for CML and
transformed the lives of many patients with this previously
fatal disease by increasing the five-year relative survival rate
from 17 percent in the mid-1970s to 63 percent in 2007
( 23). It also went on to become an effective treatment for
gastrointestinal stromal tumors (GIST), as well as several
other forms of leukemia and myeloproliferative disorders.
Equally important, imatinib helped to usher in the age of
precision medicine by becoming the first chemical agent to
target a cancer-specific protein, BCR-ABL.
What, then, is precision medicine?
Precision medicine, also known as personalized medicine,
molecular medicine, or tailored therapy, is broadly defined
as treating a patient based on characteristics that distinguish
that individual from other patients with the same disease.
Factors such as a person’s genome, his or her cancer
genome, disease presentation, gender, exposures, lifestyle,
microbiome, and other yet-to-be-discovered features
are considered in precision medicine (24) (see Figure 2).
Currently, genomics is the predominant factor influencing
precision medicine in oncology.
In essence, what precision medicine aims to do is identify
the factors most unique to the disease state and use them
for the purposes of preventing cancer, diagnosing disease,
predicting patient outcomes, and directing therapy.
Further, in the research and development setting, these
characteristics are used to develop an ever-expanding
toolkit of increasingly more precise anticancer therapeutics
(see Appendix Table 1, p. 122). In other words, by
understanding more about a particular disease, one should
be able to develop “magic bullets” specific for that disease
that would leave healthy tissue unharmed, a concept
pioneered over 100 years ago by Paul Ehrlich, the father of
chemotherapy for disease ( 25).
Over the course of more than 60 years, we have gone
from a limited understanding of the specific factors that
influence cancer development to a greater appreciation of
the particular genetic mutations that can fuel a cancer (see
Figure 3, p. 25, and (Re)Setting the Standard of Care, p. 26).
With this more precise knowledge of cancer development,
the tools used to prevent, detect, diagnose, and treat cancer
have also become more precise.
Although precision medicine is not unique to the practice
of oncology, oncology is leading such efforts largely
because of our immense knowledge of the role of genetic
mutations in the development and progression of cancer
(see Developing Cancer, p. 18). When this fact is coupled
with our increasing ability to read all parts of a person’s
genome faster than ever before, it becomes clear that
genomics is and will continue to be a key driver of precision
medicine. It should be noted, however, that genetics is but
one of the many factors relevant to precision medicine (see
Figure 2). As our ability to analyze all aspects of these other
characteristics rapidly catches up with our current genomic
prowess, we can expect faster and broader implementation
of precision medicine, not only in oncology, but also in the
treatment of other diseases.