Breast cancers among very young premenopausal women (United States)

To assess risk factors for breast cancer among very young compared to older premenopausal women.

Between 1990 and 1992 a population-based case-control study conducted in Atlanta, GA, Seattle/Puget Sound, WA, and central NJ interviewed 3307 premenopausal women aged 20-54 years. Logistic regression models estimated adjusted relative risks (RR) and 95% confidence intervals (CI) for each of three 10-year age groups.

Among the youngest age group (<35 years, n = 545), significant predictors of risk included African-American race (RR = 2.66: 95% CI 1.4-4.9) and recent use of oral contraceptives (RR = 2.26; 95% CI 1.4-3.6). Although these relationships were strongest for estrogen receptor-negative (ER-) tumors (RRs of 3.30 for race and 3.56 for recent oral contraceptive use), these associations were also apparent for young women with ER+ tumors. Delayed childbearing was a risk factor for ER+ tumors among the older premenopausal women (Ptrend < 0.01), but not for women <35 years in whom early childbearing was associated with an increased risk, reflecting a short-term increase in risk immediately following a birth. Family history of early-onset breast cancer was more strongly associated with risk among women <35 years (RR = 3.22) than those 45-54 years (RR = 1.51). Risk factors for premenopausal breast cancer not significantly modified by age at diagnosis included early age at menarche, low body mass index, and heavy alcohol consumption.

These findings suggest the possibility that women who develop breast cancers at very young ages may be etiologically as well as clinically distinct.