Declaration of interests TA reports consulting or advisory roles, or both, and received honoraria from Amgen, AstraZeneca, Bristol Myers Squibb, Chugai, Clovis Oncology, GlaxoSmithKline, Gritstone Oncology, HalioDx, Pierre Fabre, Roche/Ventana, Sanofi, Servier, Tesaro and Merck Sharp & Dohme, a subsidiary of Merck & Co, Kenilworth, NJ, USA (MSD); travel, accommodations, and expenses from Roche/Ventana, Bristol Myers Squibb, and MSD; speaker bureau fees from Bristol Myers Squibb and Servier; and research funding from MSD. TA also reports participation in the scientific committee of the ARCAD foundation and GERCOR group as non-renumerated activities. MA is an employee of Merck Sharp & Dohme, a subsidiary of Merck & Co, Kenilworth, NJ, USA, and is a shareholder in Merck & Co, Kenilworth, NJ, USA. JMN is an employee of Merck Sharp & Dohme, a subsidiary of Merck & Co, Kenilworth, NJ USA, and may own stock or hold stock options, or both, in the Company. K-KS reports honoraria from Bristol Myers Squibb, Guardant Health, Innovent Biologics, Merck KGaA, Roche, and Servier; consulting or advisory roles, or both, for Roche; research grants or funding, or both, from Amgen, Bristol Myers Squibb, Gilead, Merck KGaA, Roche, and MSD; and travel, accommodations, and expenses from Merck KGaA, Innovent Biologics, and MSD. TWK reports research grants or funding, or both, from Merck Serono, AstraZeneca, and Pfizer. BVJ reports research grants or funding, or both, from MSD. LHJ reports research grants or funding, or both, to his institution from 2cureX, Incyte, Bristol Myers Squibb, and MSD. CJAP reports advisory roles for Nordic Pharma. DS declares no competing interests. RG-C has provided scientific advice, attended speakers bureau, or received honoraria from AAA, Advanz Pharma, Bayer, Bristol Myers Squibb, HMP, Ipsen, Merck & Co, Midatech Pharma, Novartis, PharmaMar, Pfizer, Pierre Fabre, Roche, Sanofi, Servier, and MSD; and has received support to his institution for the conduct of clinical trials or for molecular diagnostic platforms from ARMO Biosciences, AstraZeneca, Pfizer, Novartis, Ipsen, Roche, Pharmacyclics, Boston Biomedicals, Merck & Co, Amgen, Sanofi, Bayer, Bristol Myers Squibb, Boehringer Ingelheim, Sysmex, Gilead Sciences, Servier, Adacap, VCN, Lilly, Pharmamar, and MSD. RG-C also reports financial support from Pfizer and Bristol Myers Squibb to an investigator-initiated trial evaluating axitinib in neuroendocrine tumours and nivolumab in neuroendocrine carcinomas. RG-C also reports being a member of the Executive Committee of the Spanish Neuroendocrine Tumor Cooperative Group (GETNE), the Executive Committee of the European Society of Neuroendocrine Tumors (ENETS), the Scientific Advisory Group for Oncology (SAG-O) of the European Medicines Agency (EMA; 2008–17), EORTC, ASCO, ESMO, SEOM, TTD, GEMCAD; and is a global PI of a clinical trial of Axitinib (Pfizer) in neuroendocrine tumours and a clinical trial of nivolumab (Bristol Myers Squibb) and chemotherapy in neuroendocrine carcinomas. IS reports advisory or consultancy, or both, roles for Ipsen, Pfizer, Syrtex, Amgen, and Pharmamar; and speaker bureau fees from AAA, Sanofi, and Novartis. CDLF reports advisory or consultancy, or both, roles for Roche, Pierre Fabre, Oncologie, Eisai, Bayer, and MSD; and travel, accommodations, and expenses from Amgen, Eisai, Bristol Myers Squibb, and Roche. FR reports honoraria; advisory or consultancy roles, or both; research grants or funding, or both; travel, accommodations, and expenses from Roche, Merck-Serono, Sanofi, Bristol Myers Squibb, Servier, Lilly, Amgen, Bayer, Celgene, and MSD. EE reports personal financial interests, honoraria, advisory roles, travel grants, and research grants from Hoffman-La Roche, Sanofi, Aventis, Amgen, Merck Serono, Servier, Array Pharmaceuticals, Bristol Myers Squibb, and MSD; and institutional financial interests and honoraria from Hoffman-La Roche, Sanofi Aventis, Amgen, Merck Serono, Boehringer Ingelheim, AbbVie, Array Pharmaceuticals, Pierre Fabre, Novartis, Bristol Myers Squibb, GlaxoSmithKline, MedImmune, and MSD. LAD is a member of the board of directors of Personal Genome Diagnostics and Jounce Therapeutics. LAD is a compensated consultant to PGDx, 4Paws (PetDx), Innovatus CP, Se'er, Kinnate, and Neophore. LAD is an uncompensated consultant to Merck & Co. LAD has received research support for clinical trials from Merck & Co. LAD is an inventor of multiple licensed patents related to technology for circulating tumour DNA analyses and mismatch repair deficiency for diagnosis and therapy from Johns Hopkins University. Some of these licenses and relationships are associated with equity or royalty payments directly to Johns Hopkins and LAD. LAD holds equity in Personal Genome Diagnostics, Jounce Therapeutics, Thrive Earlier Detection, Se'er, Kinnate and Neophore. LAD's spouse holds equity in Amgen. The terms of all these arrangements are being managed by Johns Hopkins and Memorial Sloan Kettering in accordance with their conflict of interest policies. TY reports research funding from Novartis Pharma, MSD, Sumitomo Dainippon Pharma, Chugai Pharmaceutical, Sanofi, Daichi Sankyo, Parexel International, Ono Pharmaceutical, and GlaxoSmithKline. EVC reports advisory board roles for Array, AstraZeneca, Bayer, Biocartis, Bristol Myers Squibb, Celgene, Daiichi Sankyo, Halozyme, GlaxoSmithKline, Incyte, Ipsen, Lilly, Merck KGaA, Novartis, Pierre Fabre, Roche, Servier, Sirtex, Taiho, and MSD; and research funding from Bayer, Boehringer Ingelheim, Celgene, Ipsen, Lilly, Merck KGaA, Novartis, Roche, Servier, and MSD. PY is an employee of MSD China Holding. MF is an employee of Merck Sharp & Dohme, a subsidiary of Merck & Co, Kenilworth, NJ USA, who may own stock or hold stock options, or both in the Company. DTL reports advisory board roles for MSD and Bristol Myers Squibb; research funding from MSD, Bristol Myers Squibb, Aduro Biotech, Curegenix, Medivir, and Nouscom; honoraria from MSD; and is an inventor of licensed intellectual property from Johns Hopkins University.