Soft tissue leiomyosarcomas and malignant gastrointestinal stromal tumors:Differences in clinical outcome and expression of multidrug resistance proteins

Purpose: Several studies have reported clinical behavior and chemotherapy r esistance in leiomyosarcomas, but these studies did not differentiate betwe en soft tissue leiomyosarcomas (LMS) and malignant gastrointestinal stromal tumors (GIST), Multidrug resistance (MDR) has been associated with the exp ression of p-glycoprotein (P-gp), multidrug resistance protein (MRP1), and lung resistance protein (LRP). The aim of the present study wets to compare LMS and GIST with respect to clinical outcome and MDR parameters. Patients and Methods: Clinical outcome wets evaluated in 29 patients with a primary deep-seated LMS and 26 patients with a primary malignant GIST. Par affin-embedded material, available for 26 patients with LMS and 25 with GIS T, was used for immunohistochemical detection of p-gp, MRP1, LRP, and c-kit . Results: Mean overall survival (OS) was 72 months for LMS patients and 31 m onths for GIST patients (P < .05). Metastases occurred in 16 (59%) of 27 as sessable LMS patients and in 10 (56%) of 18 assessable GIST patients. LMS p redominantly metastasized to the lungs (14 of 16 patients), whereas GIST te nded to spread to the liver (five of 10 patients) and the abdominal cavity (three of 10 patients; P < .001), p-gp and MRP1 expression was more pronoun ced in GIST than in LMS (P < .05): the mean percentage of p-gp expressing c ells was 13.4% in patients with LMS and 38.4% in patients with GIST, and th e mean percentage MRP1 expressing cells was 13.3% in patients with LMS and 35.4% in patients with GIST, LRP expression did not differ between LMS and GIST. c-kit was expressed in 5% of the LMS patients and in 68% of the GIST patients. Conclusion: LMS patients have a better survival than GIST patients, and the metastatic pattern is different Expression of MDR proteins in LMS is less pronounced than in GIST. (C) 2000 by American Society of Clinical Oncology.