Clinical prognostic factors in metastatic gastrointestinal stromal tumors (GIST) patients treated with Imatinib

Abstract

19500 Background: Imatinib (IMT) therapy is the main successful therapy for metastatic GIST. We analyze the results of the treatment according to the clinical factors and dose of IMT. Methods: 38 patients (pts) with metastatic GIST (C-KIT positive) were treated from June 2001 to June 2005 with IMT; 11 pts received 400 mg bid and 27 pts 400 mg daily. Evaluation of c-Kit mutation on exon 11 was analyzed in 23 pts. An analysis of the clinical factors was performed. Results: The average age was 60 y. (18–78); Gender: 26 male/12 female; Primary location in small bowel 24, gastric 12, esophagus 2. ECOG 0–1 in 87% of pts. 31 pts have had radical surgery at the primary (26 R0, 5 R1). Interval to metastatic/local relapse was 10 months (2–61). Hepatic metastases were presented in 26 pts (1–5 in 12, 6–10 in 5, >10 in 9 pts); peritoneal disease in 26 pts (1–5 in 10, 6–10 in 8, >10 in 7 pts); pulmonary metastases in 2, bone in 2 and nodal in 3 pts; local tumor in 6. With a median follow-up of the 56 m, response rate was 5 complete, 21 partial responders, 7 disease stabilization. Three pts died in the first month of treatment, two due to tumoral bleeding, one due to progressive disease. Median survival (MS) was 43 (0–54) months, not achieved for pts in 400 mg, 41 months for 400 mg bid pts (p=0.61). Progression free survival (PFS) was 21 months (21 for pts in 400 mg, 20 for pts in 400 mg bid). We don’t find statistical differences regarding the number of hepatic and peritoneal metastases, neither according to the size of metastases (<10 cm was 48 m., ≥10 cm was 41 m.). MS was not achieved in 18/23 patients with exon 11 mutation vs 9 months for non-mutation patients (p 0.00). No differences were found in survival for 4/18 pts with missense mutation. Conclusions: Mutational status may predict the outcome of GIST patients treated with IMT. Dose of IMT, mass size and number of metastases were not prognostic factors for survival. Special attention would be done to the risk of bleeding at the start of treatment with IMT. No significant financial relationships to disclose.