Correlation of Src activation with response to dasatinib, capecitabine, oxaliplatin, and bevacizumab in advanced solid tumors

Abstract

BACKGROUND: Src inhibition may augment sensitivity to chemotherapy, but in unselected patients (pts) with advanced solid tumors, src inhibitors have shown limited clinical activity. Biomarkers to predict benefit from src inhibitors in advanced solid tumors are not yet known. METHODS: 22 pts (dose escalation cohort= 12 pts; colorectal cancer [CRC] expansion cohort= 10 pts) were enrolled in a phase I study to determine the safety and tolerability of the src inhibitor dasatinib with capecitabine, oxaliplatin, and bevacizumab (J Clin Oncol 29: 2011 [suppl; abstr 3586]). Src activation (src-a) was assessed in tumors from 16 evaluable pts. Src-a was measured by immunohistochemistry (IHC) in formalin-fixed, paraffin-embedded tumor samples using an antibody that selectively recognizes the active conformation of src (clone 28). A GI pathologist who was blinded to pt outcomes graded membranous src-a using a standard semi-quantitative method. The endpoint of this exploratory analysis was objective response rate ([ORR]= PR+CR). 2-sided Fisher’s Exact test was used to evaluate the association between ORR and src-a. RESULTS: Across all tumor types, 8 tumors had no/faint src-a (IHC=0/1); 8 tumors had moderate/strong src-a (IHC 2). Benign colonic epithelium had no src-a (IHC=0). The ORR was 75% (6/8) for pts with moderate/strong src-a versus (vs) 0% (0/8) for pts with no/faint src-a (p =0.007). In the CRC expansion cohort, the ORR was 83% (5/6) for patients with moderate/strong src-a vs 0% (0/2) for pts with no/faint src-a (p=0.107); progression free survival range was 7.9-24.4 months for pts with moderate/strong src-a. CONCLUSIONS: In this small phase I study, src-a is associated with benefit from the combination of dasatinib and oxaliplatin-based chemotherapy. Further evaluation of dasatinib in patients whose tumors demonstrate high levels of src-a may be warranted. Clinical trial information: NCT00920868.