Abstract LB-213: Plasma soluble VEGFR1 is a potential dual biomarker of response and toxicity for bevacizumab with chemoradiation in locally advanced rectal cancer

We explored plasma and urinary concentration of four members of the vascular endothelial growth factor (VEGF) family as potential response and toxicity biomarker of bevacizumab with neoadjuvant chemoradiation in patients with localized rectal cancer. The levels of VEGF, placental growth factor (PlGF) and soluble VEGF receptors 1 and −2 (sVEGFR1 and sVEGFR2) were measured by multiplex array in plasma and urine at baseline and during treatment. Pre-treatment values and changes over time were analyzed as potential biomarkers of pathological response to treatment (evaluated histologically using ypT, Mandard and N scoring at surgery) as well as for all acute toxicities in patients with locally advanced rectal cancer treated prospectively from 2002 to 2008 with bevacizumab, 5-fluorouracil and radiation therapy prior to surgery in a phase I/II trial (N=32 patients). Of all biomarkers, the pretreatment plasma sVEGFR1 - an endogenous blocker of VEGF and a factor linked with “vascular normalization” - was strikingly associated with both tumor regression and with the number of adverse events after preoperative (neoadjuvant) bevacizumab and chemoradiation. Thus, plasma sVEGFR1 is a strong candidate as the first biomarker to stratify patients for bevacizumab therapy. Therefore, future studies of bevacizumab and/or cytotoxics should be further explore sVEGFR1 as biomarker in neoadjuvant setting as well as in metastatic disease. This study was partially supported by NIH grants R21-CA99237, P01-CA80124, R01-CA115767, R01-CA85140, R01-CA126642 and Federal Share/NCI Proton Beam Program Income grants, and by the National Foundation for Cancer Research. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-213.