The National Cancer Database14 (link) cohort included those having noninflammatory, invasive, nonmetastatic breast cancer, having surgical treatment as their first modality ≤6 months after their diagnosis date. Patients were included if breast cancer was their first and only malignancy, and if diagnosis and treatment (all or part) was at the reporting facility. Patients without lymph node surgery or whose staging, diagnosis method, or treatment order was unknown were excluded. The NCDB does not provide a diagnosis date, but after 2002 recorded the length of the interval between diagnosis and surgery. This interval length was present for cases diagnosed from 2003 onward. The NCDB requires follow-up of >5 years, so the cohort only included cases from 2003–2005 with follow-up through 2010.
The NCDB contains the most extensive surgery (e.g. a lumpectomy followed by mastectomy lists the patient as having a mastectomy). The NCDB also contains interval lengths from diagnosis to first surgery and from diagnosis to definitive surgery, to determine if the patient underwent >1 procedure. We excluded patients with >1 breast surgery to ensure capture of therapeutic surgery and to eliminate possible confounding excisional biopsies, ensuring that the analysis evaluated the time to therapeutic surgery. Patients receiving neoadjuvant chemotherapy were excluded, and chemotherapy and radiotherapy use were defined as being administered if given ≤1 year after surgery. Missing covariate data is listed ineTable 2 .
Adjustments were made for age, sex, race, income, education, size of metropolitan area, geographical region, year of diagnosis, Charlson-Deyo comorbidity score, histology, grade, tumor size, surgical margins, number of nodes examined, number of nodes positive, AJCC stage, surgery type, chemotherapy, radiotherapy, endocrine therapy, facility type, distance to facility, class of case, and insurance type, via propensity score based weighting.
The NCDB contains the most extensive surgery (e.g. a lumpectomy followed by mastectomy lists the patient as having a mastectomy). The NCDB also contains interval lengths from diagnosis to first surgery and from diagnosis to definitive surgery, to determine if the patient underwent >1 procedure. We excluded patients with >1 breast surgery to ensure capture of therapeutic surgery and to eliminate possible confounding excisional biopsies, ensuring that the analysis evaluated the time to therapeutic surgery. Patients receiving neoadjuvant chemotherapy were excluded, and chemotherapy and radiotherapy use were defined as being administered if given ≤1 year after surgery. Missing covariate data is listed in
Adjustments were made for age, sex, race, income, education, size of metropolitan area, geographical region, year of diagnosis, Charlson-Deyo comorbidity score, histology, grade, tumor size, surgical margins, number of nodes examined, number of nodes positive, AJCC stage, surgery type, chemotherapy, radiotherapy, endocrine therapy, facility type, distance to facility, class of case, and insurance type, via propensity score based weighting.