Objective: The purpose of this article is to assess tumor changes on perfusion CT with bevacizumab and interferon (IFN) therapy in patients with metastatic carcinoid tumors and to evaluate perfusion CT differences between the two therapies.
Subjects and methods: In a phase 2 clinical trial, 44 patients were randomized to receive monotherapy with bevacizumab or IFN for 18 weeks (stage 1), followed by dual-therapy with both drugs (stage 2). Twenty-four patients consented to have optional perfusion CT examinations, which were undertaken at baseline and 18 weeks and at intervening 2 days (bevacizumab arm) or 9 weeks (IFN arm), and subsequently at 2 days after the addition of bevacizumab (IFN arm) and 9 weeks after the addition of IFN (bevacizumab arm). Tumor blood flow, blood volume, and permeability were evaluated.
Results: In the bevacizumab arm (n = 12), mean (± SD) blood flow reduced significantly after 2 days compared with baseline (16.2 ± 6.9 vs 32.3 ± 21.3 mL/min/100 g; p = 0.02), a 41.4% reduction (p < 0.0001) that was relatively fixed. Blood volume was similarly reduced from baseline values (2.8 ± 1.3 vs 4.3 ± 2.1 mL/100 g; p = 0.02), a 27.9% reduction (p < 0.02). Both measures remained essentially unchanged at 18 weeks. Similar changes in blood flow and blood volume were observed with the addition of bevacizumab in stage 2. No significant changes in blood flow or blood volume were detected in the IFN arm (n = 12), and no significant changes in permeability were detected in either arm.
Conclusion: Perfusion CT detects significant changes in perfusion parameters in metastatic carcinoid tumors treated with bevacizumab. Such changes are apparent just 2 days into therapy, are sustained, and are significantly different from those associated with IFN treatment. Tumor blood flow decreased with bevacizumab treatment by a relatively fixed percentage relative to baseline measurements.