Relationship between socioeconomic deprivation and outcomes for 41,109 patients with cancer enrolled in clinical trials with uniform access to protocol-directed treatment shows that patients from the highest socioeconomically deprived areas had a 28% increased risk of death compared with trial patients in the most affluent areas. Initial access to quality cancer care as represented by treatment in a clinical trial is insufficient to eliminate the disparate outcomes related to socioeconomic deprivation. Policies to mitigate socioeconomic differences in cancer outcomes should emphasise access to cancer care services beyond initial therapy according to SWOG researchers, who published their findings on 17 March 2021 in the Journal of Clinical Oncology.
The researchers led by Joseph M. Unger of the SWOG Statistics and Data Management Center in Seattle, WA, US wrote in the background that patients with cancer from socioeconomically deprived areas have limited access to screening and treatment services, tend to have more advanced disease at diagnoses and have worse cancer outcomes. Evidence suggests that the disparities persist even after accounting for individual-level socioeconomic variables such as insurance status. An important and unresolved question is whether these disparate outcomes remain after accounting for access to quality cancer care.
The study team used data from the patients participating in cancer treatment clinical trials to systematically examine whether patients from poor areas experienced worse outcomes. Patients in trials have uniform access to protocol-guided care and are uniformly staged to limit potential differences in underlying health status. These advantages enable investigators to account for the confounding influences of inconsistent pre-treatment evaluation, care, and post-treatment surveillance.
The researchers examined survival outcomes for patients enrolled in phase III and large phase II clinical trials for major cancers conducted by the SWOG Cancer Research Network from 1985 to 2012. Socioeconomic deprivation was measured using trial participants' residential zip codes linked to the Area Deprivation Index (ADI).
Five-year overall survival (OS), progression-free survival (PFS), and cancer-specific survival (CSS) were examined using Cox regression frailty models, adjusting for age, sex, and race, and separately for insurance status, prognostic risk, and rural or urban residency.
In total, 41,109 patients from 55 trials comprising 24 cancer histology and stage-specific cohorts were included in the analysis. Compared with trial participants in the most affluent areas, trial participants from areas with the highest socioeconomic deprivation had worse OS (hazard ratio [HR] 1.28, 95% confidence interval [CI] 1.20 to 1.37, p < 0.001), PFS (HR 1.20, 95% CI 1.13 to 1.28, p < 0.001), and CSS (HR 1.27, 95% CI 1.18 to 1.37, p < 0.001).
The results were similar after adjusting for insurance status, prognostic risk, and rural or urban residency. There was a continuous increase in risk of all outcomes as the ADI quintile increased.
Overall, these findings suggest that initial access to protocol-guided therapy in a clinical trial is not by itself sufficient to eliminate the disparate outcomes related to deprivation. Future research should examine whether the cause of this disparity is related to reduced access to supportive care or post-protocol therapy and/or to differences in health status not reflected by protocol staging criteria.
The study was supported by the US National Cancer Institute of the National Institutes of Health, American Cancer Society and in part by The Hope Foundation for Cancer Research.
Unger JM, Moseley AB, Cheung CK, et al. Persistent Disparity: Socioeconomic Deprivation and Cancer Outcomes in Patients Treated in Clinical Trials. JCO; Published online 17 March 2021. DOI: 10.1200/JCO.20.02602.