CASE REPORT

Molecular response of gastrointestinal stromal tumour after treatment with tyrosine kinase inhibitor imatinib mesylate

P Reichardt¹, U Schneider², C Stroszczynski³, D Pink¹ and P Hohenberger⁴

¹ Division of Medical Oncology, Hematology, and Tumour Immunology, Robert Roessle Hospital and Tumour Institute, Charité University Hospital, The Humboldt University at Berlin, D-13122 Germany
² Pathology Laboratory, Robert Roessle Hospital and Tumour Institute
³ Department of Radiodiagnostics, Robert Roessle Hospital and Tumour Institute
⁴ Division of Surgery and Surgical Oncology, Robert Roessle Hospital and Tumour Institute

Correspondence to:
Correspondence to:
Professor P Hohenberger
Division of Surgery and Surgical Oncology, Charité, University Medicine Berlin, Campus Berlin-Buch, Lindenberger Weg 80, D-13122 Berlin, Germany; hohenberger{at}rrk-berlin.de

Bleeding from the tumour site is not uncommon during the treatment of gastrointestinal stromal tumours with imatinib mesylate. It might represent an early reaction of highly vascularised tumour tissue to receptor blockade. Although often requiring emergency surgery, this is not necessarily a deleterious sign. Slow tumour regression and cystic tissue alteration may follow. Using immunohistochemistry and consecutive resection specimens, it was shown that the number of mitoses decreased significantly and MIB-1 as a marker of cell proliferation could no longer be detected. In the few tumour cells still present, the magnitude of expression of the pathognomonic marker CD117 remained unchanged. Decreases in the size of tumours responding to imatinib mesylate cannot be expected to meet the World Health Organisation or RECIST (response evaluation criteria in solid tumours) criteria. This underlines the necessity of functional imaging by positron emission tomography, contrast enhanced magnetic resonance imaging, or magnetic resonance spectroscopy to assess the response to treatment.

Keywords: gastrointestinal stromal tumour; imatinib; response

Abbreviations: GIST, gastrointestinal stromal tumour; Hb, haemoglobin; IHC, immunohistochemistry; MRI, magnetic resonance imaging

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