(CHICAGO, IL) — Patients with annual household incomes below $50,000 were less likely to participate in clinical trials than those with annual incomes of $50,000 or higher, and were more likely to be concerned about how to pay for such participation, according to results of a large national survey of people with cancer reported at the 2012 American Society of Clinical Oncology Annual Meeting.

“Prior research has shown some association between cancer clinical trial enrollment and income, but the income measures were indirect. This is the first time in a large national study that we have actual patient-reported income on which to base this finding,” said lead author, Joseph M. Unger, MS, SWOG Statistical Center and the Fred Hutchinson Cancer Research Center, Seattle, WA. “Our study found that after accounting for all factors such as age, education, sex, race, medical conditions, and distance to a clinic, income on its own was associated with a patient’s clinical trial participation.”

The study, a collaboration between SWOG and NexCura, assessed patterns of clinical trial treatment decision-making using “important” socioeconomic factors—age, sex, race, income, and education—in a sample of 5,499 patients surveyed from 2007-2011. The survey was conducted via a web-based treatment decision tool; all data were self-reported. Eligibility included a new diagnosis of breast, lung, colorectal, or prostate cancer and age ≥18 years. “Reasons for nonparticipation in clinical trials were assessed using prespecified items about treatment, family, cost, and logistics,” Unger said.

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Results showed 40% of those surveyed discussed clinical trials with their physicians; 45% of these discussions led to offers of clinical trial participation and 51% of the offers led to actual participation. Overall, the rate of clinical trial participation was 9%, Unger noted, which differed by age (10% for <65 years vs 5.4% for >65 years; P=0.002), income (10.0% for >$50,000/year vs 7.6% for <$50,000/year; P=0.001), and education (9.6% for college education vs 7.9% for less than a college education; P=0.02). Patients who earned <$20,000 annually were 44% less likely to participate in clinical trials than patients who made >$20,000.

In a multivariate model that included all socioeconomic status and demographic factors—plus the covariates comorbidity status and “distance to clinic” as a surrogate for convenience—income remained a predictor of clinical trial participation (OR 0.73; P=0.01). “Even in patients >65 [years], who are nearly universally covered by Medicare, lower income predicted reduced clinical trial participation,” he said. “Cost concerns were much more evident among lower income patients (P=0.0001).”

A better understanding of why income is a barrier may help identify ways to make clinical trials available to all patients and would increase the generalizability of clinical trial study results across all levels of socioeconomic status, Unger concluded.

While this study did not assess what specific cost concerns led patients not to participate in trials, possible barriers may include direct costs, such as co-pays and co-insurance, or indirect costs, such as having to take time off work to go for a clinic visit, although these costs are also borne by those              undergoing cancer treatment outside of clinical trials.