Racial/Ethnic and Age Disparities in Chemotherapy Selection for Colorectal Cancer

Nour A. Obeidat, PhD; Francoise G. Pradel, PhD; Ilene H. Zuckerman, PhD; James A. Trovato, PharmD, MBA, BCOP; Francis B. Palumbo, PhD, JD; Sylvain DeLisle, MD, MBA; and C. Daniel Mullins, PhD
Published: Thursday, Mar 03, 2011
Studies1-8 have evaluated racial/ethnic and age disparities in whether patients receive chemotherapy for nonmetastatic colo-rectal cancer (CRC) treatment and have found that patients of nonwhite race/ethnicity and older patients are less likely to receive chemotherapy. However, these studies did not evaluate specific types of chemotherapy agents used.

Management of metastatic (stage IV) CRC historically has involved 5-fluorouracil–leucovorin as the standard chemotherapy,9-11 but the introduction of various novel add-on chemotherapies with improved efficacy has led to an increase in the chemotherapeutic options available to manage stage IV CRC.12,13 Irinotecan hydrochloride, approved in 1998 as a second-line agent for metastatic CRC treatment and approved in 2000 as a first-line agent for use with 5-fluorouracil–leucovorin,14 was the first of these novel agents to show improved efficacy relative to 5-fluorouracil–leucovorin alone.15,16 Irinotecan inhibits the enzyme necessary for the reversible breakage and relegation of DNA strands during DNA synthesis, leading to significant improvement in tumor progression slowing and median survival time (approximately 3 additional months relative to the 5-fluorouracil–leucovorin regimen).14 Its availability, as well as the subsequent availability of other novel agents such as oxaliplatin, bevacizumab, and cetuximab, has raised expectations for more efficacious regimens than 5-fluorouracil–leucovorin alone.17-20 Nevertheless, these novel agents also place patients at higher risk of experiencing adverse effects as a result of their increased toxic effects.15,16,17-20

Knowledge is scarce about racial/ethnic and age disparities in the receipt of newer chemotherapies. Addressing this gap by examining the first of the newer agents marketed for treatment of advanced CRC disease can provide an understanding of healthcare disparities among specific services for CRC management. In addition to knowing whether patients are receiving chemotherapy in real-world settings, it is important to know whether newer chemotherapies are being selectively utilized among chemotherapy users, particularly elderly patients in whom incidence of the disease is high.21

This study sought to determine whether racial/ethnic and age disparities existed in the selection of specific types of chemotherapy among elderly patients with stage IV CRC. Given that irinotecan was the first novel agent to be available at the start of the study period, newer therapy was designated as irinotecan-containing chemotherapy. It was hypothesized that patients of African American race/ethnicity and older patients with stage IV CRC would have a lower likelihood of receipt of newer chemotherapy than white patients and younger patients.

Data Source

The linked Surveillance, Epidemiology, and End Results (SEER)-Medicare database was used for this study.22 SEER data provided clinical and demographic information about patients with cancer from SEER registries across the following 16 geographic areas: Connecticut, Detroit (Michigan), Hawaii, Iowa, New Mexico, Seattle (Washington), Utah, Atlanta (Georgia), rural Georgia, Kentucky, Louisiana, New Jersey, greater California, and Los Angeles, San Jose, and San Francisco (California). Health utilization information for these patients was obtained from their Medicare Part A and Part B claims, which include hospital services, physician and other noninstitutional provider services, and outpatient institutional providers.22

Study Population

A total of 112,345 patients with at least 1 diagnosis of nonappendiceal colon or rectal cancer occurring between 1998 and 2002 were initially identified from SEER. Patients diagnosed at death were excluded (n = 1104 patients), as were patients diagnosed as having nonadenocarcinomas or a stage of disease that did not require any chemotherapy treatment (n = 39,755). Patients younger than 66 years also were excluded to allow a complete year of data during the year before CRC diagnosis to identify prediagnosis comorbidities (n = 10,600).

Patients who were ineligible for Medicare fee for service were excluded, as were those with no utilization information because of death or loss of Medicare eligibility occurring during the same month of diagnosis (n = 22,140). To ensure that chemotherapy use was specifically for stage IV CRC, patients with a history of cancer dating 5 years or earlier before the current CRC diagnosis or patients with a concurrent cancer occurring in the same year as the CRC diagnosis were excluded (n = 3883). The final sample was further refined to those eligible to receive first-line irinotecan-containing chemotherapy (ie, patients with stage IV disease diagnosed after 1999 [n = 5068]).

Outcome Variable

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