Distribution and prognostic value of histopathologic data and immunohistochemical markers in gastrointestinal stromal tumours (GISTs): An analysis of the EORTC phase III trial of treatment of metastatic GISTs with imatinib mesylate

RationaleThe 62005 EORTC phase III trial, comparing two doses of imatinib in patients with advanced GIST, reported a median progression-free survival of 25 months with a trend towards dose dependency for progression-free survival. The current analysis of that study aimed to assess whether histological/immunohistochemical parameters correlate with clinical response to imatinib.Patients and methodsPre-treatment samples of GISTs from 546 patients enroled in phase III study were analysed for immunohistochemical characteristics, correlations with clinicopathological data, with survival and with tumours’ genotype.ResultsThere was no correlation between immunomorphological or clinical characteristics and response to treatment, PFS or OS. No correlations between immunophenotype of the tumour and PFS or OS in the two dose arms were observed.ConclusionsThe results confirm the heterogeneity of GIST in terms of immunophenotypic expression, but indicate that these parameters have no impact on the outcome of the patients under imatinib treatment.