Abstract 4127: Bolus high-dose neoadjuvant sunitinib treatment overcomes potential for rebound growth during pre-surgical treatment breaks

Abstract

Abstract Preclinical and clinical studies have suggested that stopping antiangiogenic therapy may lead to rapid revascularization and rebound tumor growth in certain instances. However, the implications for these findings remain unclear. It is possible that treatment rebounds may impact disease progression following neoadjuvant therapy, where drugs are administered for short periods and then halted prior to surgical removal of a primary tumor. Indeed, recent retrospective clinical studies have suggested that neoadjuvant antiangiogenic treatment discontinuation increases vascular proliferation and, in turn, might increase post-surgical disease progression and metastasis. However, this hypothesis has not been studied experimentally in clinically relevant mouse models of metastatic disease. We examined the effect of treatment discontinuation in the neoadjuvant setting using approved vascular endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitors (TKIs) such as sunitinib. Our studies utilized models of spontaneous metastatic breast, melanoma, and kidney cancer following surgical removal of orthotopically grown primary tumors. Neoadjuvant sunitinib treatment periods were 14 days in duration (60 mg/kg) with treatment breaks of 0, 3, 7, and 11 days compared. Pre-surgical molecular and cellular biomarkers were investigated as potential surrogates for post-surgical metastatic disease progression. These included tumor and vascular cell Ki67 and CD31 expression, as well as circulating tumor cells (CTCs) and myeloid derived suppressor cells (MDSCs). Our results show that VEGF RTKI neoadjuvant treatment benefits observed pre-surgically (such as reduction in primary tumor growth) did not consistently correlate with post-surgical survival and reduced metastatic recurrence. The addition of treatment breaks prior to surgery had positive or negative impact on post-surgical survival depending on the tumor model used. Interestingly, high-dose bolus (3 day) neoadjuvant sunitinib (120 mg/kg) treatment consistently improved post-surgical benefits when compared to sustained treatments, despite gaps in therapy. Finally, our results show that tumoral CD31+/Ki67+ cells, CTCs, and MDSCs may serve as surrogate markers of metastatic potential and predict the impact of treatment cessation on disease recurrence. Citation Format: Michalis Mastri, Amanda Tracz, Li Shen, Roberto Pili, John M.L. Ebos. Bolus high-dose neoadjuvant sunitinib treatment overcomes potential for rebound growth during pre-surgical treatment breaks. [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 4127. doi:10.1158/1538-7445.AM2015-4127