Abstract 571: Circulating proteins in response to combined-modality therapy in locally advanced rectal cancer identified by antibody array screening
Authors: Kalanxhi Erta , Hektoen Helga Helseth , Meltzer Sebastian , Dueland Svein , Redalen Kathrine Roe , Flatmark Kjersti , Ree Anne Hansen 
Published: August 2015

Abstract
Background: In treatment of locally advanced rectal cancer (LARC) with chemoradiotherapy (CRT) followed by surgery, local recurrence rates are low but development of metastatic disease remains a dominant cause of failure. The attempt of improving survival outcome by increasingly complex multimodality programs is at the price of extended limits of treatment intensity and patient tolerance. Prediction biomarkers of efficacy and toxicity might therefore assist in achieving more individualized treatment in LARC.
Methods: In a prospective LARC study (NCT00278694) composed of neoadjuvant chemotherapy (NACT; two cycles of the Nordic FLOX regimen) before long-course CRT in order to intensify treatment, serial serum samples were collected from 87 cases at baseline, following NACT (post-NACT), at CRT completion (post-CRT), and at evaluation of the neoadjuvant treatment 2-4 weeks before surgery. Anticipating that proteins were released into the circulation from the tumor as well as from other tissues as an adverse response to the combined-modality therapy, the serum samples were analyzed using an antibody array detecting a variety of 507 proteins (RayBiotech® AHH-BLG-1 array). Alterations in circulating protein profiles during the neoadjuvant treatment were correlated to progression-free survival (PFS) and treatment toxicities as assessed by Common Terminology Criteria for Adverse Events (CTCAE) scoring. Median follow-up was 63 months.
Results: Significant changes in serum protein levels (as compared to baseline) were observed during the treatment course, with the numerically greater alterations found post-CRT. Gene ontology analysis of the altered proteins showed that the majority were involved in immune system processes and extracellular matrix organization. Interestingly, the levels of lipocalin-2 (LCN2) and matrix metalloproteinase-9 (MMP9) were significantly lowered during the entire treatment course with post-NACT median fold change decline to 0.46 and 0.38 for LCN2 and MMP9 respectively, followed by a gradual increase towards baseline values post-CRT and at evaluation before surgery. On univariate cox regression analysis, post-NACT values (fold change from baseline) of LCN2 and MMP9 were entered as continuous data, and for both factors, the lower the value the better PFS with a hazard ratio for a PFS event of 2.8 and 2.3, respectively. Both components (the Nordic FLOX regimen and pelvic CRT) of the neoadjuvant treatment protocol would cause intestinal toxicity, but the individual patient's post-NACT decline in LCN2 and MMP9 serum levels did not predict CTCAE grade 3 diarrhea at CRT completion when the highest incidence of treatment-induced enteropathy was recorded.
Conclusion: Antibody array analysis of serial serum samples from the neoadjuvant treatment course represented a ‘liquid biopsy’ insight into systemic responses to intensified combined-modality therapy in LARC.
Citation Format: Erta Kalanxhi, Helga Helseth Hektoen, Sebastian Meltzer, Svein Dueland, Kathrine Roe Redalen, Kjersti Flatmark, Anne Hansen Ree. Circulating proteins in response to combined-modality therapy in locally advanced rectal cancer identified by antibody array screening. [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 571. doi:10.1158/1538-7445.AM2015-571