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Angiopoietin-2 early increase to predict benefit from regorafenib in metastatic colorectal cancer (mCRC) patients: The prospective REGOLAND study.

e15566 Background: Regorafenib is a treatment option for refractory mCRC patients with no validated predictors of benefit. We previously showed that, among several circulating angiogenic factors, low baseline Ang-2 and Tie-2 plasma levels were associated with good prognosis and that the early increase of Ang-2 during the treatment could predict benefit from regorafenib ( Antoniotti et al, J Clin Oncol 36:675-675, 2018). To prospectively validate these retrospective findings, we conducted the REGOLAND study. Methods: Ang-2 and Tie-2 were assessed by ELISA on plasma samples collected at baseline (d1) and after 15 days (d15) of treatment in a cohort of mCRC patients receiving regorafenib, as per indication. To detect a HR for PFS of 0.50 in favour of the early increase (Δd15-d1) of Ang-2 levels, setting two-sided α = 0.05 and β = 0.10, 87 events were required according to Schoenfeld design. Comparisons among concentrations of each marker at d1 and d15 were performed by Wilcoxon test. Median values at baseline were used as cut-off to discriminate patients with low versus high plasma levels and their correlation with outcome was analysed. Results: One hundred patients were included. Median PFS and OS were 2.5 and 6.7 months, respectively. The early increase of Ang-2 at d15 was reported in 42 patients and was associated with longer PFS (median 2.7 vs 2.4 months; HR for PFS: 0.72 [95%CI:0.48-1.08], P = 0.095). As compared to d1, an overall decrease of Tie-2 levels at d15 was observed ( P = 0.007), but it was not associated with clinical outcome. Low levels of Ang-2 at baseline were associated with longer PFS (HR: 0.59 [95%CI:0.39-0.89], P = 0.005) and OS (HR:0.62 [95%CI:0.41-0.94], P = 0.017), while Tie-2 levels were not. In the multivariate model, the association of Ang-2 levels with PFS was confirmed (HR:0.48 [95%CI:0.31-0.76], P = 0.001), but not with OS (HR: 0.80 [95%CI:0.49-1.28], P = 0.351). Conclusions: Ang-2 is a prognostic marker and its early modulation predicts clinical benefit among mCRC patients treated with regorafenib. We hypothesize that Ang-2 levels early increase as a consequence of the successful inhibition of Tie-2 by regorafenib that leads to a compensatory increase of the ligand and correlates with anti-tumour activity.