dramatically improve patient care; however, in order for
these advances to continue at a rapid pace, the challenge of
patient enrollment in clinical trials must be addressed.
Inadequate patient accrual is a major obstacle to all clinical
trials and, in particular, to continued success in the
development and approval of molecularly based drugs.
Unfortunately, fewer than 5% of adults diagnosed with
cancer participate in a clinical trial, despite the fact that
clinical trials are an opportunity to receive the latest and
most innovative treatments for their disease.
Low patient participation in clinical trials, particularly in
underserved and minority populations and geriatric patients,
is a major hurdle that must be addressed. There are many
reasons why patients do not participate in clinical trials: fear
of side effects, lack of awareness, lack of physician
awareness or encouragement, bothersome trial
requirements, ineligibility, language or cultural barriers, age,
and race (see Aging and Cancer, p. 65 and Cancer
Disparities Sidebars, p. 64).
Overall, today’s advances in cancer treatment have given us
a window into the future of cancer care, and these
discoveries are only the beginning. Personalized cancer
medicine is still in its early stages of development. As
fundamental science continues to provide more molecular
information about the biology of cancer, we will witness the
further development of unimaginable advances in molecular
therapeutics and diagnostic tools, all of which will facilitate
the needed precision when choosing the best treatment for
an individual patient’s cancer.
Molecularly Based Prevention
Our increasing understanding of the unique biological
processes of cancer cells has enhanced methods to assign
tumors to specific subtypes, enhanced and expanded the
process of cancer drug development, and improved patient
care. It has also begun to provide a molecular profile of a
American Association for Cancer Research
Aging and the
Development of Cancer
Cancer incidence and prevalence increase with age. Currently, 60% of
all cancers occur in the 13% of the population, aged 65 and older. By
2030, this group is estimated to grow to 20% of the U.S. population
and account for more than 70% of all new cancer diagnoses10.
There are 3 primary reasons why cancer is more common in older
• Cancer is not an event; it is a process that occurs over time. Tissues
are exposed to a variety of insults throughout one’s lifetime; thus,
older tissues have had a longer period in which to accumulate
harmful mutations that may cause cancer.
• Due to the lifetime accumulation of acquired mutations in the
various cellular repair processes, aging tissues may be more
susceptible to the effects of carcinogens later in life because they
are unable to effectively repair DNA damage.
• In addition to decreased DNA repair, aging tissues exhibit decreased
surveillance by the immune system and increased insulin
resistance, all of which may favor the development of cancer.
One of the most important advances in cancer care for the elderly
has been the development of new tools that can predict how well a
patient will respond to chemotherapy. Such tests examine the
likelihood of treatment complications, the risk of chemotherapy-related toxicities, and the mortality risk for a given patient, making it
easier to choose the appropriate course of treatment. Among these
tools are tests that examine leukocyte telomere length and circulating
The course of disease is different for younger and older populations,
and co-morbidities that tend to accumulate with age also need to be
considered when making treatment decisions. For example, elderly
patients with acute myelogenous leukemia have a poorer prognosis
because their cancer cells are more resistant to chemotherapy than
those of younger patients. Interestingly, in the case of some breast
cancers, older individuals may have a better prognosis than younger
patients because of differences in the tumor microenvironment.
Our ability to successfully treat older patients has advanced with
improved surgery and radiotherapy; targeted therapies with limited
toxicity; improved palliative care; more protection from chemotherapy-induced mucositis which leads to weight loss and malnutrition; and a
better understanding of long-term complications of cancer treatment.
In order to continue to improve cancer care for older individuals, we
must address the economic, cultural, social, and other factors that
have precluded their enrollment in clinical trials. We must also build a
large database of elderly patients, as this will allow us to study
prognosis and treatment effectiveness in this population for the
benefit of all.
Collectively, these advances have increased survival and, importantly,
improved the quality of life by facilitating the medical and personal
independence of older cancer patients, an increasing component of
the U.S. population.