Complementary approaches to assessing risk factors for interval breast cancer.
OBJECTIVE
To examine risk factors for interval breast cancer among women screened in a population-based mammography program.


METHODS
Risk for interval cancer was assessed in terms of both the incidence per 10,000 negative screens and the proportion of all breast cancers diagnosed among screened women. Interval (N = 557) and screen-detected cancers (N = 1,545) were identified among 208,667 women receiving mammography in Colorado (1994-2001). Logistic regression was used to assess independent effects of multiple factors.


RESULTS
Overall risk of interval cancer was 29.5/10,000 women screened. Incidence was higher in women >50 years (OR: 2.28, 1.86-2.80), with family history (OR: 2.23, 1.85-2.70), with dense breasts (OR: 3.84, 2.76-5.35), and using hormones (OR: 1.54, 1.20-1.97). Hispanics had lower incidence than Whites (OR: 0.52, 0.34-0.81). Interval cancers represented 26% of all cancers diagnosed. This proportion was higher in women <50 (OR: 1.41, 1.09-1.82) and in women with dense breasts (OR: 2.95, 1.94-4.48).


CONCLUSIONS
Incidence of interval cancer increases with age, breast density, hormone use, and family history. Attempts to reduce occurrence of these cancers through more sensitive and/or intensive screening should focus on these subgroups. The disproportionate number of interval cancers associated with young age and dense breasts suggests these cancers result from both rapid growth and difficulties in detection.
Colorado School of Public Health, University of Colorado, Denver, CO, USA. jan.lowery@ucdenver.edu
Jan T
JT
Lowery
Tim
T
Byers
John E
JE
Hokanson
John
J
Kittelson
John
J
Lewin
Betsy
B
Risendal
Meenakshi
M
Singh
Judy
J
Mouchawar
D000328:Adult; D000367:Age Factors; D000368:Aged; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D015994:Incidence; D008327:Mammography; D008403:Mass Screening; D008875:Middle Aged; D012307:Risk Factors