Comorbidities Impede Clinical Trial Participation Among Patients With Cancer

Clinical trial participation is crucial for drug development, but it’s estimated that just 5% of patients participate in clinical trials. While institutional factors, such as lack of a locally available trial, play the largest role, patient characteristics also pose barriers to participation. According to a study published in JAMA Oncology, patients with comorbidities are less likely to have clinical trial discussions with their physicians, have trials offered to them, and participate in them.

Including patients with comorbidities in clinical trials has gained attention as the American Society of Clinical Oncology (ASCO), Friends of Cancer Research, and the FDA have established a working group to design clinical trial eligibility to better reflect real-world populations. This would include modernizing criteria routinely used to exclude patients with HIV, brain metastases, organ dysfunction, and prior cancer.

According to the study, assuming a cancer incidence of 1,735,350 new cases in the United States in 2018 and a trial participation of 5% on average, removing comorbidity restrictions on ASCO-recommended categories would allow up to 6317 more patients to enroll in clinical trials. These categories include hepatic dysfunction, renal dysfunction, cardiovascular disease, and prior cancer.

“At least 60% of trial eligibility exclusions pertain to patient comorbidities or performance status,” explained the researchers of the study. “Some amount of selection bias is inevitable to maintain patient safety, but modernizing trial eligibility criteria could expand access to trials and speed their conduct.”

Using data from a large national survey of 5499 patients with a first diagnosis of breast, colorectal, lung, or prostate cancer, the researchers examined the patient decision-making process about clinical trial participation.

More than half (66%) of patients had 1 or more of the 18 included comorbidities, of which hypertension (35%) was the most common. Other common conditions with a prevalence of more than 10% included vision loss, arthritis, asthma, hearing loss, and prior cancer. The researchers noted that cardiac conditions were rarer, including bypass surgery, heart attack, and heart failure.

Less than half of patients (39.5%) reported that they had discussed a trial with their physician, while 17.8% reported being offered trial participation and 9% reported actually participating in a trial.

“In almost all cases, the presence of a comorbid condition was associated with lower observed rates of trial discussion (16 of 18 instances), trial offer (17 of 18), and trial participation (16 of 18),” noted the researchers.

While 44.1% of patients without comorbidities had trial discussions, 37.2% of patients with comorbidities had those discussions. Trials were offered to 21.7% of patients with no comorbidities compared with 15.7% of patients with comorbidities, and trial participation occurred for 11.3% of patients with no comorbidities compared with 7.8% of patients with comorbidities. The comorbidities most strongly associated with these 3 scenarios were hypertension, prior cancer, and hearing loss. Other factors associated with trial participation were cardiovascular conditions and arthritis.

The researchers also examined what the impact on clinical trial participation would be if patients were not excluded for their comorbidities. Based on ASCO criteria, if there were no renal restrictions, there would be a 0.88% increase. More substantial increases were seen with no lung restrictions (2.75%), cardiovascular restrictions (3.87%), prior cancer restrictions (4.15%), and ASCO category restrictions (7.28%). No comorbidity restrictions would lead to an increase of 13.82%.

Reference

Unger J, Hershman D, Fluery M. Association of patient comorbid conditions with cancer clinical trial participation [published online January 10, 2019]. JAMA Oncol. doi: 10.1001/jamaoncol.2018.5953.