Bone metastases from gastrointestinal stromal tumors (GISTs).

Abstract

e20527 Background: Liver and peritoneum are the most common site of recurrences from gastrointestinal stromal tumors (GISTs). Bone metastases represent a rare finding in clinical practice and their biological significance and clinical management remain unsettled. Methods: We reviewed all patients with advanced/metastatic GIST at our institution and focused on cases with bone metastases, describing the clinical and radiological features of these lesions. Results: Among 71 patients, four had bone metastases. Two were female (82 and 54 years of age) and two were male (62 and 44 years of age). All four of them had an high-risk primary GIST, localized in small intestine in three cases, and in the stomach in the other one. One patient harboured a KIT esone 11 mutation (T>A 69429(p.V559d), one patient had a WT GIST and in the other patients mutational analysis was not assessable. Bone tumour involvement was present at the time of initial diagnosis in two patients, and occurred during the follow-up period after 7 and 2 years in the other two. In all patients bone metastases were associated to other visceral site of relapse. Radiologically, the lesions were diagnosed by CT-scan and had a lytic pattern in all cases, with a widespread skeletal involvement. In no case a single lesion was found. Clinically, bone metastases were symptomatic in three patients and presenting with a pathological fracture in a single case. In only one patient bone lesions were asymptomatic and diagnosed as occasional finding. All patients received zoledronic acid in association with TK inhibitors, obtaining a long stable disease in two cases whereas there was a quick disease progression in the other two cases. Only one patient was also treated with radiotherapy for palliative purpose. Conclusions: Although bone metastases are an infrequent site of recurrence from GISTs, they may become more prevalent due to increased patient life expectancy as well as the improvement in imaging techniques. By now their biological background and prognostic value and their clinical management are unknown. Moreover standard imaging and metabolic criteria for diagnosis and tumor response assessment are still lacking. These data should be collected in large series.