Cancer risk increases dramatically as we age. More than half of all new cancers are diagnosed in patients 65 and older, and more than 25 percent of new cases are discovered in patients 75 and older, according to the National Cancer Institute. So it’s reasonable to conclude that checkpoint inhibitors, a burgeoning class of immunotherapy drugs approved to treat several cancers in patients of all ages, may be a strong option for elderly patients, too. But that may not always be the case, says Ankur Parikh, DO, Medical Director of Precision Medicine at Cancer Treatment Centers of America® (CTCA) and Hematologist-Oncologist and Medical Oncologist at our hospital in Philadelphia.
Percent of new cancer cases by age
|Less than 20
|20 to 34
|35 to 44
|45 to 54
|55 to 64
|65 to 74
|75 to 84
Elderly patients, 65 and older, with weakened immune systems may not have the robust response to immunotherapy some younger patients experience. And because elderly patients are less likely to participate in clinical trials, less clinical data is available on why they may or may not respond to these treatments. “Immunotherapy certainly helps a lot of patients, and we're seeing very exciting responses in certain populations,” Dr. Parikh says. “What we do know is that patients’ immune systems change and evolve over time. And as someone gets older, their immune system also changes. And is someone the age of 65 going to respond the same to immunotherapy as someone who is under 40? That question hasn't been answered yet, and unfortunately, a lot of clinical trials don't have an elderly population. So we don't get those answers very often.”
Cancer risk increases with age for many reasons.
- Cell replication errors occur more often in older people, increasing the chances of producing a DNA mutation that may lead to cancer. A 2017 study by researchers at Johns Hopkins University School of Medicine concluded that errors made when cells continuously divide may be responsible for more than 60 percent of all cancers.
- Years of habits such as drinking, smoking and a poor diet take their toll. A 2016 Harvard study of about 130,000 Americans found that cancer risk may be reduced by up to 40 percent by adopting a healthy lifestyle.
- Exposures to carcinogens and environmental risk factors, such as asbestos, second-hand smoke, pesticides and ultraviolet light from the sun also increase the risk.
When we’re younger, our cells have repair mechanisms that often fix DNA mutations caused by exposure or replication errors. And when they don’t repair them, the immune system is more likely to kick in to attack the defective cells and kill them. But as we age, our repair mechanisms begin to break down and our immune systems weaken, which may allow defective cells to grow out of control and form a tumor. “I think one challenge with elderly patients is that their immune system may not be as competent, or it may undergo something called immune senescence. Senescent cells, which are not dead but are no longer growing or dividing, sometimes have precancerous characteristics. Other senescent cells, including immune cells, may exist in a zombie-like state—alive, but not functioning properly. Checkpoint inhibitors, designed to allow immune cells to better recognize and attack cancer cells, may not always provide the kickstart required to battle cancer in elderly patients with senescent immune cells. “The jury's still out on the role of immunotherapy or, specifically, checkpoint inhibitors in elderly patients,” Dr. Parikh says.
TYPES OF IMMUNOTHERAPY:
- Checkpoint inhibitors are designed to activate immune cells to better recognize and attack cancer cells.
- Vaccines are designed to either prevent viruses that may cause cancer or to attract immune cells to a tumor or cluster of cancer cells.
- Cytokines are protein molecules that help regulate and direct the immune system.
- CAR T-cell therapy uses re-engineered T cells to attack specific features on certain cancer cells.
Research on immunotherapy’s impact on older patients continues, Dr. Parikh says, but clinical data may be limited since older patients are less likely to volunteer for clinical trials. Also, elderly patients may have conditions such as chronic obstructive pulmonary disease (COPD) or heart failure that would make them ineligible for clinical trials. “So we miss out on that very important patient population,” Dr. Parikh says. Still, doctors will continue to turn to immunotherapy when appropriate as a treatment option in patients of all ages, he says. “When it works well for a type of cancer, I don't discriminate based on how old somebody is,” Dr. Parikh says. “We still give them the benefit of the doubt and try it when appropriate.”
Learn about dangerous drug interactions.