Data was gathered from the National Cancer Database (NCDB), a cancer registry based on hospital care which is sponsored by the ACS and American College of Surgeons. The NCDB includes standardized data on patient insurance state, tumor characteristics, course of treatment, outcomes, demographics, socioeconomic data, and treatment facility data. The database includes roughly 70% of newly diagnosed cancer cases in the U.S. and contains over 34 million records across over 1500 facilities. The data is collected using CoC (Commission on Cancer) program registries and is coded using their Facility Oncology Registry Data Standards. Given that no hospital, provider, patient identifiers, or protected health information was used in this study, institutional review board approval was not required. Along with the NCDB’S classifications, The Charlson-Deyo Index Score is a weighted derived from the sum of scores for a list of conditions in the Charlson Comorbidity Score Mapping Table based on the ICD-9-CM (International Class of Disease, 9th edition, Clinical Modification). This was used to assess comorbidity.
Study Population
The patient population consisted of women diagnosed with invasive breast cancer (stages I-III) between January 1, 2004 and December 31st, 2016 from within the National Cancer Database (n = 432,883). Our analysis was restricted to women older than the age of 18.
In this study, we characterized four levels of adjuvant chemotherapy delay: Less than 1 month, 1–2 months, 2–3 months, and greater than 3 months. The time was defined based on the number of days following surgical resection to the start of adjuvant chemotherapy. In addition, the year of diagnosis was reported. Age was stratified into five groups: 18–49, 50–59, 60–69, 70–79, and over 80. Patient race was characterized as non-Hispanic White or non-Hispanic Black. The primary payer or insurance type held by the patient were classified by Medicaid, Medicare for patients between the ages of 18–64, Medicare for patients 65 and older, private health insurance (preferred provider organizations and health maintenance organizations), no insurance (self-pay, charity write-off, or those who are uninsured), and those with other or unknown data regarding insurance. Of note is the distinction between Medicare patients above the age of 65 and below the age of 65, as the latter is limited to those with permanent disabilities. Regions were categorized by the US Census Bureau Regions and Divisions, which divide the country into 9 different divisions: New England, Middle Atlantic, South Atlantic, East North Central, East South Central, West North Central, West South Central, Mountain, and Pacific. The regions were further classified into four regions: Northeast- Middle Atlantic, New England; Midwest- West North Central, East North Central; West- Pacific, Mountain; South- East South Central, West South Central, South Atlantic. The American Joint Commission on Cancer (AJCC) cancer stage was also included (Stage I, II or III). Based on the registry reporting of pre-existing comorbidities drawn from hospital discharge reports, the Charlson-Deyo comorbidity index was reported. Also related to the specific health status of the patient, their hormone receptor status (positive/borderline, negative, or no test available) was included in the analysis.
Additional social determinants of health were included in the collected patient data. Patient income was grouped into less than $38,000, $38,000-$47,999, $48,000-$62,999, and $63,000 +. Further, the proportion of the population in a particular ZIP Code, based on prior census data, which did not attain a high school diploma was included in the collected data. Patients were grouped according to 21% or more, 13% -20%, 7%-12%, and less than 7%. Finally, given the issues faced by geographic barriers to accessing care, the data includes information on the patient’s distance from the reporting facility.