More than 60 percent of cancer patients are older adults — and that will rise to 70 percent by 2040. Yet seniors are underrepresented in clinical trials, making it difficult to assess how treatments are likely to help or harm them.

The newest evidence of the imbalance comes from a Food and Drug Administration analysis. It found that only 40 percent of patients participating in cancer clinical trials were 65 and older. The analysis was presented last month at the annual meeting of the American Society of Clinical Oncology (ASCO).

Clinical trials investigate the safety and effectiveness of new drugs and therapies, as well as ways to prevent illness and detect conditions early. Their findings help guide medical practice.

Yet, older adults are often not included in research studies to any significant extent. This is especially true for cancer patients in their 70s and 80s, according to the FDA’s data:

●While 19 percent of breast cancer patients are 75 or older, only 4 percent of breast cancer clinical trial participants are of this age.

●Although 33 percent of colon cancer patients are in the 75-and-older group, a mere 8 percent of patients studied by researchers fell into that age group.

●While 37 percent of lung cancer patients are 75 or older, only 9 percent of people of that age are represented in lung cancer clinical trials.

The sobering conclusion: “It’s difficult to practice evidence-based medicine in an older population because the data isn’t there,” said Stuart Lichtman, a professor of medicine at Weill Cornell Medical College in New York and president of the International Society of Geriatric Oncology.

And it’s not just cancer. Across medical conditions that disproportionately affect seniors, people 65 and older have a poor showing in clinical trials.

“There’s often an assumption that drugs only need to be tested in younger people and results can be extrapolated,” said Consuelo Wilkins, an associate professor of medicine at Vanderbilt University Medical Center who, with colleagues, is overseeing a major grant to help bring more seniors, blacks, Hispanics and other groups into clinical trials. “But we know that how older adults respond to medications and interventions and their risk for adverse events is different based on their physiology.”

Difficulties enrolling older people in research studies extend to Alzheimer’s disease. With research funding through the National Institutes of Health (NIH) now at nearly $1.4 billion a year, “we’re going to be seeing more and more clinical trials, but it’s already difficult to get enough people to participate,” said Keith Fargo, director of scientific programs at the Alzheimer’s Association.

Fewer than one-third of people diagnosed with Alzheimer’s are eligible to join clinical trials, he said.

Researchers often find older adults unsuitable for trials for multiple reasons: Seniors may have multiple illnesses — diabetes and hypertension in addition to cancer or Alzheimer’s disease — that could complicate the study’s results, or they may already be taking medications that could interact with therapies being examined.

Also, older adults may live alone and not have someone who can accompany them to the study site for tests and procedures — a significant concern for Alzheimer’s trials, which typically require a caregiver to provide input about the patient’s condition and progress. Also, some seniors can’t get around easily. And some are frail.

Responsibility falls to a large extent on physicians, said Richard Schilsky, chief medical officer for ASCO, noting that “they don’t ask older adults whether they want to participate or not. It’s a combination of concern that older patients might be unable to comply with a trial’s requirements, which are usually quite rigorous, and concern that specified therapies might be too toxic.”

Two years ago, ASCO issued new recommendations calling for older adults to be included in more clinical trials. But progress has been slow, acknowledged Hyman Muss, director of geriatric oncology at the Lineberger Comprehensive Cancer Center at the University of North Carolina at Chapel Hill.

“My view is that every patient I see, if they’re eligible for a clinical trial, I’ll tell them about it,” he said.

Don’t assume your doctor will be equally forthcoming. “Absolutely, you should take the initiative and ask,” Schilsky recommended. And don’t assume you need to have run out of options before doing so. “Clinical trials aren’t just for people who have no treatment options left — that’s a common misconception,” Schilsky said.

Debbie Earp, 67, joined a trial at the Lineberger this year after getting a diagnosis of Stage 2 breast cancer in early January. Her responsibilities over the four-month study: wearing a Fitbit, tracking how much exercise she was getting daily and filling out a questionnaire about how she was feeling each time she got chemotherapy.

Earp said she agreed to participate because “I’ve always exercised, and I felt, from a physical and psychological point of view, anything that was going to motivate me during treatment to exercise more would be a good idea.” The goal of the trial was to examine how physical activity affects older breast cancer patients’ response to chemotherapy.

Of course, clinical trials aren’t for everyone. Some older people are reluctant to consider them because they’re skeptical of unproven therapies. Others may choose to focus on their quality of life instead of aggressive treatments.

There are good resources about clinical trials on the Internet, if you know where to look. The National Institute on Aging has prepared materials for older people, including a list of questions that seniors should ask before deciding whether to join a trial. The FDA has a patient-oriented site that delves into issues such as informed consent — making sure you’re fully informed about the potential benefits and harms of a research study, among other essential information.

For those who want to look for trials on their own, NIH sponsors ClinicalTrials.gov, a database of studies around the world, searchable by disease and geography. Trials Today, created at Vanderbilt University, is an effort to make the NIH site more consumer-friendly. At ResearchMatch, another Vanderbilt effort, people who want to participate in studies can sign up to be matched with clinical trial sponsors. And TrialMatch, currently listing more than 250 scientific studies, is a one-stop-shop for clinical trials for people with Alzheimer’s disease, their caregivers and people interested in preventing dementia.

Make sure you run whatever prospects you find by your doctor. “Very few patients have the expertise to understand if a clinical trial is appropriate for them,” Schilsky said. “You really need an expert opinion to help you understand what you find.”

— Kaiser Health News

Kaiser Health News is a nonprofit health news service that is an editorially independent part of the Kaiser Family Foundation.