Purpose: To determine the relationship between managed care market activity and cancer trial enrollment.
Methods: Trial participant data were obtained from the National Cancer Institute. Participants in cooperative group trials of breast, colorectal, lung, or prostate cancer during the years 1996 through 2001 were assigned to counties based on their zip code of residence. Linear regression was used to determine the relationship between county enrollment rate and two measures of county managed care activity (penetration and index of competition [IOC]), adjusting for other county characteristics.
Results: In bivariate analysis, there was a strong inverse correlation between trial enrollment rate and IOC (r = -0.23; P < .001) as well as the proportion of the population uninsured (-0.31; P < .001) and the percentage below poverty (-0.16; P < .001). In the multivariate model, greater county managed care competition (IOC) was inversely related to trial enrollment rate (P < .008 for comparison of each quartile v lowest quartile) after accounting for managed care penetration, proportion uninsured, and other county characteristics. Counties in the lowest quartile of managed care penetration tended to have lower enrollment rates than the remaining counties (r = -0.05; P = .048), while counties in the second, third, and fourth quartiles of penetration all had similar enrollment rates to one another.
Conclusion: Cancer trial enrollment rates were suboptimal across all counties, and counties with higher levels of managed care competition had significantly lower enrollment rates. The relationship between managed care penetration and trial enrollment was less consistent. Future efforts to enhance trial participation should address the potential negative influence of market factors.