Ethics approval and consent to participate

This retrospective study was conducted on already available data and biological material collected during the PHERGain trial. This trial was conducted in accordance with the Declaration of Helsinki and its amendments, the International Conference on Harmonization (ICH) Good Clinical Practice (GCP) guidelines (ICH E6 GCP), and applicable local laws and regulations.

Consent to participate

Informed consent was obtained from all individual participants included in the study.

Competing interests

MG declares participation as a Consultant for Daiichi-Sankyo/AstraZeneca, Gilead, Novartis, Pfizer; receiving Honoraria from F. Hoffman La Roche and Travel grants from F. Hoffman La Roche, AstraZeneca, Pfizer. JJG-M declares Financial support for attending symposia from Lilly, Novartis, BMS, Roche, Palex; Employment or consultation from Trialing Health S.L., MEDSIR S.L. JMP-G declares Consulting or Advisory role for Lilly, Roche, Eisai, Daichii Sankyo, AstraZeneca, Seattle Genetics, Gilead, MSD; receiving Travel expenses from Roche, and Employment at MEDSIR. VP declares receiving fees as consultant, participating in advisory boards or receiving travel grants from Sysmex, Roche, MSD, AstraZeneca, Bayer, Exact Sciences, Daiichi-Sankyo. MR-B declares no conflicts of interest. AS declares Speaker’s bureau from Daiichi, Novartis, Astra Zeneca; Travel, accommodations or expenses from Eisai, Novartis, and Pfizer; Advisory role for Astra Zeneca, Boehringer Ingelheim, Novartis, Seagen, Gilead. BB declares receiving fees as consulting or advisory role for medical education from MSD, Roche, Pierre Fabre, Novartis, Astra Zeneca, Seagen; Speakers’ bureau for Pfizer, Roche, MSD, Palex, Eisai, Daichii, Astra Zeneca, Seagen. JAG, LL-M, MM and JR-M declare Employment at MEDSIR. GA declares honoraria and travel expenses from MEDSIR. MS-C declares Employment at MEDSIR and Advisory boards for Optimapharm, Ability Pharma, MD Anderson. AL-C declares Consulting/Advisory role for Roche, AstraZeneca, Seagen, Daiichi-Sankyo, Eli Lilly, Merck Sharp&Dohme, GSK, Gilead, Menarini, ExactSicences, Novartis, Agendia, Pfizer; Honararia from Roche, Novartis, Pfizer, Lilly, Daiichi Sankyo; Research funding to the Institution from Roche, AstraZeneca, Eisai, F. Hoffman-La Roche, Guardant Health, Merck Sharp&Dohme, Pfizer; Travel, accomodation, expenses from Roche, Novartis, Pfizer, Daiichi Sankyo, AstraZeneca, Gilead; and Patents: HER2 as a predictor of response to dual HER2 blockade in the absence of cytotoxic therapy. Alex Prat, Antonio Llombart, Javier Cortés. US 2019/0338368 A1. JC declares Consulting/Advisory role for Roche, AstraZeneca, Seattle Genetics, Daiichi Sankyo, Lilly, Merck Sharp&Dohme, Leuko, Bioasis, Clovis Oncology, Boehringer Ingelheim, Ellipses, Hibercell, BioInvent, Gemoab, Gilead, Menarini, Zymeworks, Reveal Genomics, Scorpion Therapeutics, Expres2ion Biotechnologies, Jazz Pharmaceuticals, Abbvie, BridgeBio; Honoraria from Roche, Novartis, Eisai, Pfizer, Lilly, Merck Sharp&Dohme, Daiichi Sankyo, Astrazeneca, Gilead, Steamline Therapeutics; Research funding to the Institution from Roche, Ariad pharmaceuticals, AstraZeneca, Baxalta GMBH/Servier Affaires, Bayer healthcare, Eisai, F.Hoffman-La Roche, Guardanth health, Merck Sharp&Dohme, Pfizer, Piqur Therapeutics,Iqvia, Queen Mary University of London; Travel, accommodation, expenses from Roche, Novartis, Eisai, Pfizer, Daiichi Sankyo, Astrazeneca, Gilead, Merck Sharp&Dhome, Steamline Therapeutics; Stock: MAJ3 Capital, Leuko (relative); Patents: Pharmaceutical Combinations of A Pi3k Inhibitor And A Microtubule Destabilizing Agent. Javier Cortés Castán, Alejandro Piris Giménez, Violeta Serra Elizalde. WO 2014/199294 A. ISSUED, Her2 as a predictor of response to dual HER2 blockade in the absence of cytotoxic therapy. Aleix Prat, Antonio Llombart, Javier Cortés. US 2019/ 0338368 A1. LICENSED. Non-financial interests: Agostina Stradella declares being a member of GEICAM’s Executive Board.