Cross-Platform Biomarker Program for Establishment and Validation of Liquid Biopsy for Clinical Decision Making in resectable gastrointestinal stromal tumour (GIST)

Interventions: Group 1: Day -30 to -1 prior to start of therapy: Screening examination for all participants. A mutational analysis of a histologic sample is performed to detect cKIT- and PDGFR-mutations (inclusion criteria). Additionally imaging methods according to local standards are performed, blood samples will be taken and participants registered. Participants with cKIT- and/or PDGFR-mutated tumours are further included: During neoadjuvant therapy and during surgical therapy: Day -1 to 0: Blood taking for ctDNA and proteins Day +6 (±2): Blood taking for ctDNA and proteins Day +14 (±2): Blood taking for ctDNA and proteins After surgical therapy: Month +3 to +60, every three months (± 28 d): imaging, blood taking for ctDNA and proteins The current medication and disease stage is ascertained at every visit. The taken blood volume is 63 mL each. Primary outcome(s): 1. detection of tumor-specific mutations in ctDNA isolated from plasma after surgical therapy Study Design: Allocation: ; Masking: ; Control: ; Assignment: ; Study design purpose: Prognosis