GOALS: To study the role of loss of heterozygosity (LOH) in serum microsatellite DNA of patients with gastrointestinal stromal tumors (GIST). BACKGROUND: In GIST, tumor markers from peripheral blood are missing. STUDY: Seventy-eight patients (59 GIST, 13 leiomyomas, 2 leiomyosarcomas, and 4 schwannomas) underwent resection at our institute between 1985 and 2006. Thirty-three preoperative sera (26 GIST and 7 non-GIST) and 62 postoperative sera (47 GIST and 15 non-GIST) were available and tested for alterations in 12 representative microsatellite loci on chromosomes 22, 17, 13, 9, and 3, using fluorescence-based automated capillary electrophoresis by ABI Prism. Survival was calculated with Kaplan-Meier plots. RESULTS: Seventeen out of 26 GIST patients had a positive preoperative serum LOH score (>/=2 LOH, sensitivity 65.4%), and 6 out of 7 non-GIST patients had a negative score (/=2 LOH preoperatively. Postoperative sensitivity and specificity of LOH analysis for prediction of relapse in 47 GIST was 75.0% and 64.1%, respectively. After a median observation time of 51.3 months (95% confidence interval, 39.4-61.4), LOH in serum significantly predicted overall survival (P=0.007, log-rank test). CONCLUSIONS: LOH serum analysis in GIST may play a role as a noninvasive, differential diagnostic, prognostic, and monitoring marker in the clinical routine.
