Purpose: Biomarker-driven master protocols represent a new paradigm in oncology clinical trials, but their complex designs and wide-ranging genomic results returned can be difficult to communicate to participants. The objective of this pilot study was to evaluate patient knowledge and expectations related to return of genomic results in the Lung Cancer Master Protocol (Lung-MAP)., Methods: Eligible participants with previously treated advanced non-small-cell lung cancer were recruited from patients enrolled in Lung-MAP. Participants completed a 38-item telephone survey ≤ 30 days from Lung-MAP consent. The survey assessed understanding about the benefits and risks of Lung-MAP participation and knowledge of the potential uses of somatic testing results returned. Descriptive statistics and odds ratios for associations between demographic factors and correct responses to survey items were assessed., Results: From August 1, 2017, to June 30, 2019, we recruited 207 participants with a median age of 67, 57.3% male, and 94.2% White. Most participants "strongly/somewhat agreed" with statements that they "received enough information to understand" Lung-MAP benefits (82.6%) and risks (69.5%). In items asking about potential uses of Lung-MAP genomic results, 87.0% correctly indicated that the results help to select cancer treatment, but < 20% correctly indicated that the results are not used to confirm cancer diagnosis, would not reveal risk of developing diseases besides cancer, and would not indicate if family members had increased cancer risk. There were no associations between sociodemographic factors and proportions providing correct responses., Conclusion: In a large National Clinical Trials Network biomarker-driven master protocol, most participants demonstrated incorrect knowledge and expectations about the uses of genomic results provided in the study despite most indicating that they had enough information to understand benefits and risks., Competing Interests: Joshua A. RothEmployment: Genentech/RocheConsulting or Advisory Role: Bristol-Myers Squibb, Bayer, Epigenomics, Seattle Genetics Meghna S. TrivediHonoraria: Onclive Stacy W. GrayStock and Other Ownership Interests: Magenta TherapeuticsHonoraria: Triptych Health PartnersConsulting or Advisory Role: Magenta Therapeutics Donald L. PatrickHonoraria: Grail, AllakosConsulting or Advisory Role: Philip Morris International Mary W. RedmanConsulting or Advisory Role: AstraZeneca Vassiliki PapadimitrakopoulouEmployment: PfizerHonoraria: RocheConsulting or Advisory Role: Clovis Oncology, Genentech, Merck, Biothera, Lilly, Janssen, Genentech, AstraZeneca, ARIAD, Nektar, Loxo, Araxes Pharma, Abbvie, Bristol-Myers Squibb, Exelixis, Pfizer, Novartis, Takeda, TRM Oncology, Tesaro, Arrys Therapeutics, Gritstone Oncology, Leads Biolabs, Bolt Biotherapeutics, G2 InnovationResearch Funding: Merck, Novartis, Celgene, Clovis Oncology, Bayer, Bristol-Myers Squibb, AstraZeneca, Pfizer, Janssen Oncology, ACEA Biosciences, Nektar, Roche, Lilly, Checkmate Pharmaceuticals, Checkmate Pharmaceuticals, Checkmate Pharmaceuticals, Incyte, Guardant HealthTravel, Accommodations, Expenses: AstraZeneca, Roche, RocheOther Relationship: Roche Karen KellyConsulting or Advisory Role: Novartis, Symphogen, Inivata, Bristol-Myers Squibb, AstraZeneca, Regeneron, EMD Serono, Takaeda, Lilly, Amgen, EMD Serono, Genmab, Targeted Oncology, Genentech, Debiopharm Group, Abbvie, Daiichi Sanko, Janssen, GlaxoSmithKlineResearch Funding: EMD Serono, Genentech, Abbvie, Five Prime Therapeutics, Regeneron, Astellas Pharma, Tizona Therapeutics, Inc, Lilly, Novartis, AmgenPatents, Royalties, Other Intellectual Property: Author Royalties for UpToDate, an evidence based, peer reviewed information resource, available via the web, desktop, and PDATravel, Accommodations, Expenses: AstraZeneca, Genentech/Roche, Merck, Regeneron, Lilly, Abbvie, EMD Serono David GandaraHonoraria: AstraZeneca, MJH Life Sciences Healthcare, CBPartnersConsulting or Advisory Role: AstraZeneca, Guardant Health, OncoCyte, Amgen, IObiotech, Merck, Roche/Genentech, Boehringer Ingelheim, Inivata, LillyResearch Funding: Roche/Genentech, Merck, AmgenTravel, Accommodations, Expenses: Boehringer Ingelheim Roy S. HerbstLeadership: Junshi PharmaceuticalsConsulting or Advisory Role: AstraZeneca, Genentech/Roche, Merck, Pfizer, Abbvie, Biodesix, Bristol-Myers Squibb, Lilly, EMD Serono, Heat Biologics, Junshi Pharmaceuticals, Loxo, Nektar, NextCure, Novartis, Sanofi, Seattle Genetics, Shire, Spectrum Pharmaceuticals, Symphogen, TESARO, Neon Therapeutics, Infinity Pharmaceuticals, ARMO Biosciences, Genmab, Halozyme, Tocagen, Bolt Biotherapeutics, I-Mab, Immunocore, Mirati Therapeutics, Takeda, Cybrexa Therapeutics, eFFECTOR Therapeutics, Candel Therapeutics, Inc, Oncternal Therapeutics, STCube Pharmaceuticals, Inc, WindMIL, XencorResearch Funding: AstraZeneca, Merck, Lilly, Genentech/Roche Dawn L. HershmanConsulting or Advisory Role: AIM Specialty Health Scott D. RamseyEmployment: Flatiron HealthConsulting or Advisory Role: Bayer, Genentech, Bristol-Myers Squibb, AstraZeneca, Merck, GRAIL, Pfizer, Seattle Genetics, BiovicaResearch Funding: Bayer, Bristol-Myers Squibb, MicrosoftTravel, Accommodations, Expenses: Bayer Schering Pharma, Bristol-Myers Squibb, Flatiron Health, Bayer, GRAILNo other potential conflicts of interest were reported.