Abstract 3598: Selective internal radiation (SIRT) is most effective when comparing local treatment to control progressive liver metastases of gastro-intestinal stromal tumors beyond treatment with tyrosine kinase inhibitors

Abstract

Abstract Objective: The liver and the peritoneum are the main area of metastatic spread in gastrointestinal stromal tumors (GIST). Liver surgery plays a minor role for hepatic metastases in comparison to f.e. colorectal cancer. However, once the metastases are resistant to 1st line TKI, surgery, 2nd line therapy, interventional ablation techniques like RFA or selective internal radiation therapy (SIRT) are treatment options. We were interested to analyze the contribution of the different modalities in controlling hepatic progression. Methods: 731 pts with biopsy proven GIST were followed since 2004 (median follow-up 43.6 months); data were prospectively documented. There were 337 males (46.1%) and 101 (13.8%) pts. presented with M1 disease initially. Of the remaining 630 pts, 358 pts (56.8%) developed tumor recurrence after a median time interval of 22 months. 312/358 pts (87%) developed metastases within the abdomen: liver n = 96, peritoneal n = 97, liver+peritoneal n = 78, locoregional n = 10, locoreg.+hep/per n = 21. Imatinib was the initial treatment in all patients with M1 disease. Results: Out of 205 patients with liver metastases, 118 remained controlled by drug therapy or showed multi-site progression. In the remaining 87 pts., 26 pts each underwent liver resection or 2nd/3rd line drug therapy (sunitinib, regorafenib), 22 pts had RFA and 13 pts were treated by SIRT. Follow-up was done via dynamic MRI and contrast-enhanced (CE)-CT. The median hepatic-progression free survival (H-PFS) was 15.9 months (4-29) after SIRT (with 3 CR, 6 PR), however, only 5.6 (range, 2 - 13) months after 2nd line drug, 8.2 (3-15) months after surgery, and 7.7 (5-14) months after RFA, p<0.02. Conclusion: 90Y radiation loaded particles (SIRT) provides the best hepatic progression free survival when compared to 2nd line drugs, RFA or even surgery in imatinib resistant GIST liver metastases. The effect could be mediated by eliminating small (subclinical, micro-) metastases. In patients known to have a GIST resistant to known TKIs, such as wildtype (non-KIT, non-PDGFRA mutated f.e. NF1-associated) lesions, SIRT could be used in earlier treatment lines. Citation Format: Peter Hohenberger, Nils Rathmann, Franka Menge, Maliha Sadick, Stefan Schönberg, Steffen Diehl. Selective internal radiation (SIRT) is most effective when comparing local treatment to control progressive liver metastases of gastro-intestinal stromal tumors beyond treatment with tyrosine kinase inhibitors. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3598. doi:10.1158/1538-7445.AM2015-3598