While older adults represent a majority of new cancer diagnoses, they are underrepresented in randomized clinical trials.
It’s estimated that by 2030, 70% of all new cancer diagnoses will occur among people aged 65 years and older. However, according to a report published in JAMA Oncology, older patients are not just underrepresented in cancer clinical trials, but the age disparities that exist within these trials are worsening.
Examining more than 200,000 patients enrolled in 302 randomized clinical trials between 1994 and 2015, researchers determined that the median age of patients in clinical trials was an average of 6.49 years younger compared with the median age of patients with the disease based on the Surveillance, Epidemiology, and End Results database. Looking over time, a linear regression model revealed an estimated annual change of —0.19 years in the difference in median age, suggesting widening age disparities.
Differences in age were more pronounced for clinical trials that were industry funded, in which the median age of patients enrolled in the clinical trials was an average of 6.84 years younger than the median age of patients with the disease in real-world populations. Non—industry-sponsored trials had an average 4.72-year difference in median age.
According to the researchers, a potential contributing factor to the increased age disparities associated with industry-funded trials might be that these trials are more easily available at centers that treat a greater proportion of younger patients. The researchers did not identify an association between industry funding and increased utilization of age-based or performance status-based enrollment criteria.
“Randomized clinical trials often establish the standard of care; with underrepresentation of older patients, concerns regarding the applicability of trial results persist,” explained the authors of the report, who noted that historically, the federal government has addressed clinical trial enrollment disparities by primarily focusing on sex and race/ethnicity.
Patients involved in the studies had breast, prostate, colorectal, or lung cancer.
With greater attention being paid to molecular subtypes of cancer, such as HER2-overexpressing cancers, and targeted therapies continuing to make up a greater share of cancer treatments, the researchers also looked at whether trials for these molecular subtypes and these agents are associated with age disparities.
Accounting for 14.9% of trials, clinical trials restricted to certain molecular subtypes were more likely to be industry funded compared with unrestricted trials (93.3% vs 81.2%). These trials were also more likely to enroll younger patients.
Among systemic therapy trials, those that assessed a targeted therapy, such as a monoclonal antibody, were associated with a larger difference in median age than those that tested cytotoxic chemotherapy (—7.72 vs –5.30 years). These targeted therapy trials were also more likely to be industry funded compared with trials assessing cytotoxic chemotherapy (93.8% vs 79.8%).
Ludmir E, Mainwaring W, Lin T, et al. Factors associated with age disparities among cancer clinical trial participants [published online June 3, 2019]. JAMA Oncology. doi: 10.1001/jamaoncol.2019.2055.