P1-08-05: Age and Survival in Women with Early Stage Breast Cancer: An Analysis Controlling for Tumor Subtype

Background: Previous research has suggested that young age at diagnosis is an independent risk factor for breast cancer recurrence and death in women with early stage breast cancer. However, young women are more likely to have aggressive subtypes of breast cancer. No prior studies have adequately controlled for tumor phenotype, including HER-2/neu (HER2) status, in particular. Recent evidence has suggested that the prognostic effect of young age varies by tumor subtype. Methods: We examined data from women with newly diagnosed Stage 1–3 breast cancer presenting to one of 8 NCCN centers between January 2000 and December 2007. Multivariate Cox proportional hazards models were used to assess the relationship between age and breast cancer specific survival, controlling for known prognostic factors and treatment. In addition, we conducted stratified analyses by estrogen receptor (ER) and HER2 status. Results: 19,633 women with Stage 1–3 breast cancer eligible for analysis including 2,177 (11%) who were age 40 years or younger at diagnosis. Younger women were more likely to be non-white or Hispanic, more educated, employed, and to have higher stage, high grade, ER-negative, progesterone receptor (PR) negative, and HER2−positive disease, and treated with chemotherapy and trastuzumab (all variables P< 0.0001 by Chi-Square test). 5-year survival among younger women was 94.1 (95% Confidence Interval [CI] 92.9−95.3) and 96.3 (95% CI 95.9−96.6) for older women. In a multivariate Cox proportional hazards model controlling for sociodemographic, disease, and treatment characteristics, women age < 40 or younger at diagnosis had increased mortality compared to older women (Hazard Ratio [HR] 1.26, 95% CI 1.02−1.56). In stratified analyses, age 40 or less was associated with increased mortality among women with ER-positive disease (HR 1.44, 95% CI 1.01−2.05), but was not among those with ER-negative disease (HR 1.15, 95% CI 0.85−1.55). Younger age was associated with a statistically significant increase in mortality among women with HER2−negative disease (HR 1.29, 95% CI 1.00−1.68), but this difference did not reach statistical significance among those with HER2−positive disease (HR 1.30, 95% CI 0.82−2.09). Conclusions: The effect of age on short-term survival of women with early breast cancer appears to vary by breast cancer subtype, particularly ER status. Further research to elucidate differences in breast cancer biology and efficacy of therapy within tumor types by age is warranted. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-08-05.