Updated publication reference for PubMed record(s): 32024067, 30979792. Mass spectrometry-based phosphoproteomics of tumor tissue lysates provides a potential personalized medicine approach based on its ability to identify activated signaling pathways and novel drug targets. We performed a pilot study (NCT01636908) to determine the effect of protein kinase inhibitors (PKIs) on tyrosine-(pTyr)-phosphoproteomic profiles of serial tumor biopsies in patients with advanced cancer. Tumor needle biopsies were analyzed from 31 patients with advanced cancer before and after 2 weeks treatment with sorafenib (SOR), erlotinib (ERL), dasatinib (DAS), vemurafenib (VEM), sunitinib (SUN) or everolimus (EVE). pTyr-Phosphoproteomics of pre- and on-treatment biopsies was performed by phosphotyrosine immunoprecipitation followed by LC-MS/MS.