Conflict-of-interest disclosure: S.K.P. reports consulting or advisory role with Seattle Genetics. J.W.F. is the Editor-in-Chief of Journal of Clinical Oncology, and the journal policy recused the author from having any role in the peer review of this manuscript; reports research funding from Enterome (institutional); and reports patents, royalties, and other intellectual property pertaining to bone marrow microenvironment signals (institutional). A.G. reports honoraria and consulting/advisory role with Takeda. E.H. reports consulting or advisory role with Merck Sharpe & Dohme (institutional), Roche/Genentech (institutional), AstraZeneca, Gilead Sciences (institutional), Bristol Myers Squibb (institutional), Servier, Novartis (institutional), BeiGene (institutional), Link Healthcare (institutional), and Antengene (institutional); speakers' bureau fees from Roche/Genentech, Regeneron, and AbbVie (institutional); and research funding from AstraZeneca (institutional), Celgene (institutional), Merck KGaA (institutional), Janssen-Cilag (institutional), Gilead Sciences (institutional), Mundipharma (institutional), Bristol Myers Squibb (institutional), and Roche/Genentech (institutional). P.J. reports honoraria from Genmab, Epizyme, and Incyte; consulting or advisory role with Epizyme; and patents, royalties, and other intellectual property regarding combined use of Fc gamma RIIb (CD32b) and CD20-specific antibodies (WO Patent, PCT/GB2011/051572; EU11760819.0). B.K.L. reports consulting or advisory role with Genentech/Roche, MEI Pharma, and Amgen; and research funding from Pharmacyclics/Janssen (institutional), Genentech/AbbVie (institutional), and Genmab (institutional). K.J.S. reports honoraria from Seattle Genetics, Roche, and Abbvie,; consulting or advisory role with Seattle Genetics, Roche and Abbvie; research funding from Bristol Myers Squibb, Seattle Genetics (institutional), Viracta (institutional), and Merck (institutional); and other relationship, including Data and Safety Monitoring Committee role, and uncompensated relationships with Regeneron. P.L.Z. reports consulting or advisory role with Celltrion, Gilead Sciences, Janssen-Cilag, Bristol Myers Squibb, Servier, Sandoz, MSD, Roche, EUSA Pharma, Kyowa Hakko Kirin, Takeda, Secura BIO, TG Therapeutics, Novartis, ADC Therapeutics, Incyte, and BeiGene; and speakers' bureau fees from MSD, EUSA Pharma, and Novartis. M.J.M. reports employment and stock/other ownership interests in Exact Sciences (immediate family member); consulting or advisory role with Bristol Myers Squibb (institutional); and research funding from Bristol Myers Squibb (institutional), Roche/Genentech (institutional), and Genmab (institutional). A.M.E. reports honoraria from Pfizer, Pharmacyclics, Research to Practice, Epizyme, Novartis, MorphoSys, Incyte, Targeted Oncology, AbbVie, Takeda, Patient Power, PER, OncLive Clinical Congress Consultants, HUTCHMED, Incyte, MorphoSys, and Daiichi Sankyo/AstraZeneca; consulting or advisory role with Pfizer, Novartis, Pharmacyclics, Incyte, Epizyme, MorphoSys, AbbVie, Incyte, and MorphoSys; and speakers' bureau fees from Research to Practice. The remaining authors declare no competing financial interests.