Safety and efficacy of percutaneous radio-frequency ablation (RFA) in patients (pts) with metastatic gastrointestinal stromal tumor (GIST) with clonal evolution of lesions refractory to imatinib mesylate (IM)

Abstract

9024 Background: IM is a highly effective treatment for metastatic/unresectable GIST. Although pts may exhibit durable systemic disease control, with time clonal evolution of lesions refractory to IM emerge and require alternative treatment approaches. We have evaluated the role of percutaneous RFA in this subset of pts with single or oligoclonal progressing GIST lesions who are in good performance status. Methods: Pts with limited sites of GIST progressing despite continuation of IM were treated with CT-guided RFA. All pts had staging with CT/MRI as well as functional imaging with 18FDG PET scans, both before and after RFA. Biopsy of the target lesions was performed before RFA. Results: Nine pts treated with imatinib for a median of 25 months (m) (range 18–36 m) underwent RFA for single or limited site(s) of progressing disease. Sites of progression: 8/9 pts with liver metastases, 1/9 with soft tissue disease. 5/9 of these pts developed a new nodule within a pre-existing GIST lesion, the remaining 4/9 had anatomic progression of pre-existing sites or developed a new site of disease. Pts undergoing the procedure were asymptomatic and had a good baseline performance status (ECOG 0–1). Progressing lesions were not 18FDG-avid by PET scanning in 5 pts. No pt developed early or late complications from the procedure. With median follow-up of 4.2 m (range 1–11 m), all pts had their lesions completely ablated. 5/9 pts progressed systemically and had an increase in their imatinib dosing (from 400 or 600mg/d to 800mg/d), resulting in disease control for an additional 1–6 m (median 3.5 m). 4 pts remain stable on continued treatment with imatinib (median follow-up 5.8 m). Conclusion: In this small cohort, percutaneous RFA appears to be a safe and effective treatment for localized sites of progression. This procedure helps to manage limited IM-resistant GIST. Continuation of IM to control systemic sites of IM-sensitive GIST despite emergence of limited clonal resistance can be justified on the basis of this exploratory work. Author Disclosure Employment or Leadership Consultant or Advisory Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Novartis Novartis; Pfizer Novartis; Pfizer