Colorectal cancer (CRC) might rank as the third most common cancer, but it is the second leading cause of cancer-related deaths in the United States. It presents significant challenges to global healthcare, with 20% of patients diagnosed at a metastatic stage and a dismal 5-year survival rate of just 15.6%. A study published in JAMA Network Open was aimed to evaluate the socioeconomic and demographic disparities in microsatellite instability (MSI) and KRAS testing among mCRC patients, it determined prediction rates of overall survival and time to progression.
Data was sourced from the National Cancer Database (NCDB), a hospital-based cancer registry that collected demographic, clinical, and pathological data for over 70% of cancer cases diagnosed in the United States. The study cohort was exempt from ethical oversight under the Common Rule, where patient data were de-identified. The study report has followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines.
This study included the patients diagnosed with CRC on or after the day 1 January 2010 and before 31 December 2017, with their faulty clinical stage IV included as the initial recommendation pertaining to metastatic disease in patients of that kind. Since CRC is only tested for MSI and KRAS biomarkers it could be inferred that available notes on the completion or noncompletion of any lab test should be included. The argument for exclusion was biomarker tests which do not date back earlier than 1 January 2010.
Basically, the NCDB implemented a change in 2018 regarding the variables for MSI and KRAS tests and stopped reporting any listed patients who did not undergo the tests. It excluded patients aged 80 years old because the allocated decision regarding conducting the biomarker test could be changed by not delivering systemic therapy. The classification of patients was according to completion or non-completion of the MSI or KRAS test experiment.
The study included 41,061 patients whose demographic characteristics are summarized as follows. Only 28.8% underwent KRAS testing and 43.7% underwent MSI testing. Among the patients, 17.3% identified as Black, 78.0% as White, and 4.7% as other racial groups. Additionally, 6.5% identified as Hispanic while 93.5% identified as non-Hispanic. Most patients (85.0%) lived in metropolitan areas. Regarding healthcare access, 43.6% were on Medicare, 40.5% received treatment at comprehensive community cancer programs, 21.3% were treated in South Atlantic facilities and 51.3% lived in areas with lower educational levels.
According to the Moffitt Criteria, greater frailty was associated with an increased likelihood of MSI testing. Factors associated with residing in areas where 17.6% or more of the population above age 25 had less than a high school education, compared to areas with only 6.3%. Patients treated at community cancer centers were less likely to receive MSI testing than those treated at academic institutions (RR, 0.74; 95% CI, 0.70-0.79; P < 0.001). Rural residency in contrast to metropolitan patient location was also associated with a decrease in the likelihood of undergoing testing for MSI (RR, 0.80; 95% CI, 0.69-0.92; P < 0.001). Patients at East South-Central hospitals were also less likely to undergo MSI testing compared to those in New England hospitals (RR, 0.67; 95% CI, 0.61-0.73; P < 0.001).
Academic facilities were significantly more likely to order the biomarker testing compared to community cancer programs (12.8 times more likely), and comprehensive community cancer programs (26.9 times more likely) following an initial diagnosis (value $5 million; P < 0.001). This data was presented at the International Society for Pharmacoeconomics & Outcomes Research (ISPOR) 2016 Annual Meeting which contributed further evidence to the disparities in testing. Only 742 survey respondents provided feedback on biomarker testing and associated shortcomings. Notably, only 45% of academic institutions and 16% of other facilities reported offering patients information about a contact person for test-related inquiries.
Older age, lower educational level in residence, treatment in community settings, and treatment at East South-Central facilities were significantly associated with lower probability of MSI and KRAS testing in this cohort study of patients with mCRC. By using national registries, we can highlight sociodemographic-based disparities in biomarker testing and outline strategies for promoting equity in cancer care and improving outcomes for underserved populations. Further studies should conduct this kind of analysis at the state level, giving priority attention to those groups or subpopulations in any way vulnerable from the socio-demographic angle.
Reference: Sabbagh S, Herrán M, Hijazi A, et al. Biomarker Testing Disparities in Metastatic Colorectal Cancer. JAMA Netw Open. 2024;7(7):e2419142. doi:10.1001/jamanetworkopen.2024.19142
