title: Comparison of clinical-pathologic characteristics and outcomes of true interval and screen-detected invasive breast cancer among participants of a Canadian breast screening program: a nested case-control study.
abstract: BACKGROUND
  Previous analyses of interval breast cancers have been limited because of a lack of control for screening interval length and patient age, failure to restrict the interval group to 'true' intervals, and incomplete descriptions of pathology, adjuvant therapies and clinical outcomes.
  
  
  METHODS
  A nested case-control study within the population-based Nova Scotia Breast Screening Program was performed. All true interval cases between 1991 and 2004 were identified, matched 1:2 to screen-detected cases (age, screening interval, time period), and compared in terms of pathologic characteristics and adjuvant therapies via logistic regression. Disease-free and overall survival was estimated, controlling for pathology and adjuvant chemotherapy receipt.
  
  
  RESULTS
  A total of 241 true interval invasive cases were matched to 481 screen-detected cases. Interval cases were more likely to be > 1 cm (odds ratio [OR] = 1.76; 95% CI, 1.10-2.83), grade 3 (OR = 2.71; 95% CI, 1.49-4.92), and have lymphovascular invasion (OR = 3.06; 95% CI, 1.85-5.07). Interval cases received more adjuvant chemotherapy (OR = 4.37; 95% CI, 3.03-6.30) and radiation (OR = 1.43; 95% CI, 1.02-2.00). The 5-year Kaplan-Meier estimates of disease-free and overall survival rates for true intervals and screens were 0.830 (95% CI, 0.770-0.875) versus 0.926 (95% CI, 0.898-0.947) and 0.860 (95% CI, 0.804-0.901) versus 0.937 (95% CI, 0.910-0.956), respectively.
  
  
  CONCLUSIONS
  True interval breast cancers have more adverse prognostic factors compared with screen-detected cases and, despite receiving more adjuvant chemotherapy, are associated with significantly poorer survival outcomes.
authors.affiliation: Division of Medical Oncology, and Atlanta Clinical Cancer Research Unit, QEII Health Sciences Centre and Dalhousie University, Halifax, Nova Scotia, Canada. daniel.rayson@cdha.nshealth.ca
authors.forename: Daniel
authors.initials: D
authors.lastname: Rayson
authors.forename: Jennifer Isabelle
authors.initials: JI
authors.lastname: Payne
authors.forename: Mohamed
authors.initials: M
authors.lastname: Abdolell
authors.forename: Penny J
authors.initials: PJ
authors.lastname: Barnes
authors.forename: Rebecca F
authors.initials: RF
authors.lastname: MacIntosh
authors.forename: Theresa
authors.initials: T
authors.lastname: Foley
authors.forename: Tallal
authors.initials: T
authors.lastname: Younis
authors.forename: Ariel
authors.initials: A
authors.lastname: Burns
authors.forename: Judy
authors.initials: J
authors.lastname: Caines
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D001940:Breast / Q000473:pathology*; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000401:mortality / Q000628:therapy*; D002170:Canada; D016022:Case-Control Studies; D055088:Early Detection of Cancer; D005260:Female; D006801:Humans; D008327:Mammography; D008403:Mass Screening; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D010641:Phenotype; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism; D011960:Receptors, Estrogen / Q000378:metabolism; D011980:Receptors, Progesterone / Q000378:metabolism; D012307:Risk Factors; D015996:Survival Rate; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone