Limitations
tumor, death
TUMOR
This study has limitations. Despite the pooled nature of this analysis, there are small sample sizes within certain strata. For example, small numbers of very young patients precluded our ability to specifically study women under the age of 40 years, a group that has been shown to exhibit differences in tumor genomics and worse BC outcomes. It is possible that such biologic heterogeneity affected outcomes in the group of women younger than 50 years.Information on cause of death could not be reliably ascertained from all 4 of the included studies and therefore we were unable to examine differences in BC-specific survival. Additionally, as specified previously, there is not documentation of how race and ethnicity were collected for participants in every trial, which may have led to misclassification of race and ethnicity in some participants.