Younger Age Does Not Significantly Impact Recurrence or Benefit from Trastuzumab in Early-stage HER2-positive Breast Cancer
Available data suggest that younger age is an independent risk factor for disease recurrence and death in women with breast cancer. However, there has not been adequate study of the interaction of age with human epidermal growth factor receptor 2 (HER2) status or anti-HER2 treatment. In an analysis of outcomes in the HERA trial in women with early-stage invasive HER2-positive breast cancer, Ann H. Partridge, MD, MPH, of Dana-Farber Cancer Institute, and colleagues found that age was not strongly associated with risk of early recurrence or benefit from trastuzumab (Herceptin) therapy. The investigators reported their findings in the Journal of Clinical Oncology.
The analysis included 1,703 women randomly assigned to 1 year of trastuzumab and 1,698 women randomly assigned to observation after completion of chemotherapy in the HERA trial. Analyses of outcomes used 2-year median data and dichotomized age at ≤ 40 years vs > 40 years.
Younger vs Older Subgroups
Overall, younger women were more likely to have had no assessment of nodal status (15% vs 10%, due to receipt of neoadjuvant therapy), less likely to have node-negative disease (28% vs 34%), and more likely to have estrogen receptor (ER)-positive (51% vs 44%) and progesterone receptor (PR)-positive disease (41% vs 32%), and were treated more often with taxanes (32% vs 25%), anthracyclines (97% vs 93%), and hormonal therapy (56% vs 49%).
No Significant Differences in Survival by Age
Uncontrolled Cox proportional hazards models showed no significant differences in disease-free survival for patients aged ≤ 40 vs > 40 years in the observation group (hazard ratio [HR] = 1.16, P = .27) or in the trastuzumab group (HR = 1.18, P = .30). No effect of age on disease-free survival was observed when age was analyzed as a continuous variable in either the observation group (HR = 0.99, P = .07) or trastuzumab group (HR = 1.004, P = .60).
Similarly, there were no significant differences in overall survival for patients aged ≤ 40 vs > 40 years in the observation group (HR = 1.05, P = .85) or trastuzumab group (HR = 1.44, P = .20). Analysis of age as a continuous variable also showed no significant effect of age on overall survival in the observation group (HR = 1.00, P = .89) or trastuzumab group (HR = 1.02, P = .16).
On multivariate analysis controlling for prognostic and predictive factors, there was no significant difference in disease-free survival for age ≤ 40 vs > 40 years in the observation group (HR = 1.18, P = .22) or trastuzumab group (HR = 1.11, P = .53). Similarly, there was no significant difference in overall survival by dichotomized age in the observation group (HR = 1.01, P = .97) or trastuzumab group (HR = 1.18, P = .58).
When an interaction term for dichotomized age and trastuzumab treatment was added to multivariate models including all patients in both treatment groups, the P values for the interaction terms were .89 for disease-free survival and .55 for overall survival, indicating that age was not a predictive factor for trastuzumab benefit. A subpopulation treatment effect pattern plot analysis of 3-year disease-free survival according to age and treatment group confirmed that differences in 3-year disease-free survival percentages between the observation and trastuzumab groups did not differ significantly across age subgroups (P = .6 for interaction).
Factors Associated with Disease-free and Overall Survival
On multivariate analysis, factors significantly associated with improved disease-free survival were ER-positive tumors in the observation group and tumor size ≤ 2 cm in both the observation and trastuzumab groups. Factors associated with worse disease-free survival were nodal status not assessed and positive nodal status in both groups and grade 3 tumors in the trastuzumab group. Factors significantly associated with overall survival in the two groups were similar except that the effect of tumor size ≤ 2 cm was borderline significant in the observation group. In addition, receipt of taxane therapy was associated with significantly poorer overall survival and receipt of anthracyclines with significantly better overall survival in the trastuzumab group.
The investigators noted that the analysis is limited by the relatively short follow-up. They concluded: “In [this] retrospective analysis of a large randomized controlled trial of women with early-stage HER2-positive breast cancer, age was not strongly associated with risk of early recurrence or prediction of benefit from trastuzumab therapy. Future research should investigate whether age is a predictor of later recurrence and evaluate the impact of age within groups with other tumor subtypes.”
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
