Treatment of metastatic, imatinib refractory, gastrointestinal stroma tumor with image-guided high-dose-rate interstitial brachytherapy

Abstract Purpose Evaluation of efficacy and safety of CT- or MRI-guided high-dose-rate interstitial brachytherapy (iBT) in the treatment of advanced, imatinib refractory, metastatic gastrointestinal stroma tumors (GISTs) was the objective of this retrospective study. Methods and Materials A cumulative number of 40 unresectable metastases (30 hepatic, 10 peritoneal) were treated with iBT in 10 selected patients with histologically proven GISTs. Six patients had peritoneal disease, and 5 patients were even progressing under sunitinib (second line)—thus iBT was applied as a salvage maneuver. IBT uses an interstitially introduced 192 iridium source in a high-dose-rate irradiation regime to destroy vital cells in a single fraction. Response to treatment was assessed clinically and with acquisition of MRI/CT every 3 months. Results Local tumor control was reached in 97.5% of all treated metastases during a median time of 25 months—only one local relapse was observed during followup. The median diameter of the irradiated lesions was 2.4 cm (range 0.6–11.2 cm); a median dose of 15 Gy (range 6.7–21.96 Gy) was applied. The median progression-free survival after iBT was 6.8 (range 3.0–20.2) months; the median overall survival was 37.3 months (range 11.4–89.7). Two major complications (Common Terminology for Adverse Events grade 3) occurred following the intervention: local hemorrhage and pneumothorax, successfully dealt with by angiographic embolization and pleural drainage, respectively. Conclusions In selected patients with metastatic, imatinib refractory GISTs, iBT safely enables high rates of local tumor control and presents an alternative, anti-neoplastic treatment option even in a salvage situation.