title: Delayed Initiation of Adjuvant Chemotherapy Among Patients With Breast Cancer.
abstract: OBJECTIVE
  Adjuvant chemotherapy improves outcomes of patients with breast cancer. However, the optimal timing of chemotherapy initiation is unknown. Delayed administration can decrease the benefit of cytotoxic systemic therapies.
  
  
  OBJECTIVE
  To identify the determinants in delayed chemotherapy initiation and to determine the relationship between time to chemotherapy (TTC) and outcome according to breast cancer subtype. We hypothesized that prolonged TTC would be associated with adverse outcomes.
  
  
  METHODS
  In an observational, population-based investigation using data from the California Cancer Registry, we studied a total of 24 843 patients with stage I to III invasive breast cancer diagnosed between January 1, 2005, and December 31, 2010, and treated with adjuvant chemotherapy. Data analysis was performed between August 2014 and August 2015.
  
  
  METHODS
  Time to chemotherapy was defined as the number of days between surgery and the first dose of chemotherapy, and delayed TTC was defined as 91 or more days from surgery to the first dose of adjuvant chemotherapy. We evaluated overall survival and breast cancer-specific survival. Logistic regression and Cox proportional hazard models were used.
  
  
  RESULTS
  In all, 24 843 patients were included. Median age at diagnosis was 53 years, and median was TTC was 46 days. Factors associated with delays in TTC included low socioeconomic status, breast reconstruction, nonprivate insurance, and Hispanic ethnicity or non-Hispanic black race. Compared with patients receiving chemotherapy within 31 days from surgery, there was no evidence of adverse outcomes among those with TTC of 31 to 60 or 60 to 90 days. Patients treated 91 or more days from surgery experienced worse overall survival (hazard ratio [HR], 1.34; 95% CI, 1.15-1.57) and worse breast cancer-specific survival (HR, 1.27; 95% CI, 1.05-1.53). In a subgroup analysis according to subtype, longer TTC caused patients with triple-negative breast cancer to have worse overall survival (HR, 1.53; 95% CI, 1.17-2.00) and worse breast cancer-specific survival (HR, 1.53; 95% CI 1.17-2.07).
  
  
  CONCLUSIONS
  For patients with breast cancer, adverse outcomes are associated with delaying initiation of adjuvant chemotherapy 91 or more days. Delayed TTC was particularly detrimental among patients with triple-negative breast cancer. The determinants of delays in chemotherapy initiation appeared to be sociodemographic, and clinicians should provide timelier care to all patients.
authors.affiliation: Department of Health Services Research, The University of Texas MD Anderson Cancer Center, Houston2Breast Medical Oncology Department, The University of Texas MD Anderson Cancer Center, Houston.
authors.forename: Mariana
authors.initials: M
authors.lastname: Chavez-MacGregor
authors.affiliation: Cancer Prevention Institute of California, Fremont.
authors.forename: Christina A
authors.initials: CA
authors.lastname: Clarke
authors.affiliation: Cancer Prevention Institute of California, Fremont.
authors.forename: Daphne Y
authors.initials: DY
authors.lastname: Lichtensztajn
authors.affiliation: Department of Health Services Research, The University of Texas MD Anderson Cancer Center, Houston2Breast Medical Oncology Department, The University of Texas MD Anderson Cancer Center, Houston.
authors.forename: Sharon H
authors.initials: SH
authors.lastname: Giordano
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000401:mortality / Q000601:surgery; D002140:California / Q000453:epidemiology; D017024:Chemotherapy, Adjuvant; D005260:Female; D006801:Humans; D016462:Mammaplasty; D008875:Middle Aged; D012042:Registries; D013997:Time Factors; D016896:Treatment Outcome; D064726:Triple Negative Breast Neoplasms / Q000188:drug therapy / Q000401:mortality / Q000601:surgery