Survival Assessment
[Blinded for peer review] data were linked to the National Death Index (NDI) based on name, social security number, date of birth, sex, race, and state of residence to identify deaths through December 31, 2013. The NDI is a national file of identified death record information, including cause of death compiled from computer files submitted by State Vital Statistics offices. Greater than 75% of the [Blinded for peer review] cases were perfect or near-perfect NDI matches on social security number, date of birth, and sex. The remaining near-matches were confirmed by examining the United States Social Security Death Index and obituaries on newspaper websites. We chose 5-year overall survival as our endpoint for this study, as there is a decreased contribution by the tumor to overall survival after this timepoint. Disease-specific survival was not available for this analysis secondary to lack of data on specific cause of death for patients in [Blinded for peer review].