Financial disclosures: Matthew D. Galsky certifies that all conflicts of interest, including specific financial interests and relationships and affiliations relevant to the subject matter or materials discussed in the manuscript (eg, employment/affiliation, grants or funding, consultancies, honoraria, stock ownership or options, expert testimony, royalties, or patents filed, received, or pending), are the following: Bradley McGregor has served as an advisory board member and consultant for Astellas, AstraZeneca, Bayer, Exelixis, Genentech, Janssen, Nextar, Pfizer, Eisai, Dendreon, BMS, Calithera, and Seagen; and has received research funding from BMS, Calithera Biosciences, Exelixis, and Seagen. Peter H. O’Donnell has acted as a consultant and advisory board member for Merck; has equity ownership in AbbVie (formerly Allergan); has received honoraria from Astellas, AstraZeneca, Atheneum Partners, Dedham Group, FirstWord Publication, Genentech, Harrison Consulting Group, Health Advances, Inovio, Janssen, Kantar Health, Merck, OncLive, Parexel, Pfizer, Quintiles, Schlesinger Associates, and Seagen; has received research funding from Acerta, Astellas, AstraZeneca, BMS, Boehringer Ingelheim, Genentech, Janssen, Merck, and Seagen; and has other relationships with Janssen, Dragonfly, and Nektar. Arjun Balar has served as an advisory board member and consultant for Astellas, AstraZeneca, Cerulean Pharma, Genentech, Incyte, Merck, Pfizer, EMD-Serono, Bristol-Myers Squibb, GSK, and Seagen; has received honoraria from AstraZeneca, Genentech, and Merck; and has received research funding from AstraZeneca, Genentech, Merck, and Seagen. Daniel Petrylak has served as an advisory board member and consultant for Astellas, AstraZeneca, Bayer, Bellicum Pharma, Dendreon, Exelixis, Ferring, Johnson & Johnson, Lilly, Millennium, Medivation, Pfizer, Roche, Sanofi, and Tyme; has equity ownership in Bellicum Pharma and Tyme; has received research funding from Agensys, Astellas, Medivation, AstraZeneca, Bayer, Clovis onc, Dendreon, Endocyte, Genentech, Innocrin Pharma, Johnson & Johnson, Lilly, MedImmune, Millennium, Merck, Novartis, Pfizer, Progenics, Roche, Sanofi, Seagen, and Sotio; and has provided expert testimony for Celgene and Sanofi. Jonathan Rosenberg has served as an advisory board member and consultant for Astellas, AstraZeneca, Bayer, Boehringer Ingelheim, BMS, EMD Serono, Genentech/Roche, Gilead/Immunomedics, GSK, Janssen, Lilly, Merck, Mirati, Pfizer, Pharmacyclics, QED Therapeutics, Tyra Biosciences, and Seagen; has received honoraria from Medscape, Peerview, RTP, and UpToDate; has received research funding from Agensys, AstraZeneca, Bayer, Genentech, Incyte, Mirati Therapeutics, QED, and Seagen; and has received travel expenses from BMS and Genentech. Evan Y. Yu has served as a consultant or advisor for Janssen, Bayer, Merck, Dendreon, Seagen, Clovis, Advanced Accelerator Applications, Exelixis, Abbvie, and Sanofi; and has received institutional research from Daiichi Sankyo, Dendreon, Taiho, Pharmacyclics, Blue Earth, Bayer, Merck, and Seagen. David Quinn is an employee of the University of Southern California; has received institutional research funding from Seagen, MSD, and Novartis; has served as an advisor/board member for Astellas, AstraZeneca, Bayer, BMS, Dendreon, Exelixis, Roche, Janssen, MSD, Novartis, Pfizer, and Sanofi; and has received travel and accommodation expenses from Pfizer, MSD, AstraZeneca, BMS, and Roche. Elisabeth I. Heath has served as a consultant or advisor for Agensys; has received honoraria from Bayer AG, Dendreon, Sanofi, and Seagen; has served on a speaker bureau for Sanofi; has received institutional research funding from Tokai Pharmaceuticals, Seagen, Agensys, Dendreon, Genentech, Roche, Millennium, Celldex, Inovio Pharmaceuticals, Celgene, Zenith Epigenetics, Merck, AstraZeneca, Esanik, Oncolys BioPharma, Curemeta, BMS, eFFECTOR Therapeutics, Fortis, Astellas Pharma, Medivation, AstraZeneca, Ignyta, Synta, Caris Life Sciences, Boehringer Ingelheim, GlaxoSmithKline, Merck Sharp & Dohme, Plexxikon, Corcept Therapeutics, and Infinity Pharmaceuticals; and reports other relationships with Caris Centers of Excellence. Mary Campbell is an employee of Seagen and owns stock in the company. Zsolt Hepp is an employee of Seagen and owns stock in the company. Caroline McKay is an employee of Astellas Pharma and owns stock in the company. Joyce Steinberg is an employee of Astellas Pharma and owns stock in the company. Antoine Regnault is an employee of Modus Outcomes, which received consulting fees from Seagen in connection with this study. Flora Mazerolle is an employee of Modus Outcomes, which received consulting fees from Seagen in connection with this study. Matthew Galsky has served as an advisory board member and consultant for Aileron Therapeutics, Astellas, AstraZeneca, BioMotiv, BMS, Dendreon, Dracen, EMD Serono, Genentech, GSK, Incyte, Inovio Pharma, Janssen, Lilly, Merck, Novartis, NuMab, Pfizer, and Seagen; has equity ownership in Rappta Therapeutics; holds patents/royalties for Methods and compositions for treating cancer and related methods (20120322792); and has received research funding from AstraZeneca, BMS, Dendreon, Genentech, Janssen, Merck, and Novartis.