Abstract C101: Circulating tumor necrosis factor receptor (TNFR) proteins in systemic disease outcome to combined-modality radiotherapy in rectal cancer
Authors: Meltzer Sebastian , Kalanxhi Erta , Hektoen Helga Helseth , Dueland Svein , Flatmark Kjersti , Redalen Kathrine Røe , Ree Anne Hansen 
Published: May 2016

Abstract
Introduction: In colorectal cancer, the impact of the tumor microenvironment with its immune effectors for disease outcome is increasingly acknowledged. Following curatively intended combined-modality radiotherapy in locally advanced rectal cancer (LARC), metastatic disease still remains a dominant cause of failure. Therefore, within the frame of a prospective LARC study of intensified neoadjuvant therapy (NCT00278694), and in light of intriguing recent findings of radiation effects on systemic antitumor immunity, we investigated whether treatment toxicity and survival outcome might be reflected by circulating immune factors.
Experimental procedures: Using antibody array technology, the profiling of approximately 500 proteins was performed in serial serum samples collected during neoadjuvant chemotherapy (NACT; two cycles of the Nordic FLOX regimen) followed by long-course chemoradiotherapy (CRT) before final pelvic surgery. Array data was analyzed in the Significance Analysis of Microarrays algorithm, and functional associations among proteins were explored using the Search Tool for the Retrieval of Interacting Genes and Proteins software. Clinical endpoints were progression-free survival (PFS; median follow-up of 59 months for 85 patients) and treatment toxicities as assessed by Common Terminology Criteria for Adverse Events (CTCAE) scoring.
Results: Analysis of the array data revealed significant changes in levels (relative to baseline) of a number of serum proteins during the neoadjuvant treatment course, among which osteoprotegerin (OPG; TNFRSF11B) showed the strongest increase. Single-parameter immunoassay OPG assessment demonstrated significant correlations between its baseline serum levels (range 13.6-177 pg/ml) and patients' age as well as common markers of systemic inflammation, such as erythrocyte sedimentation rate (ESR) and neutrophil-to-lymphocyte ratio (NLR). In univariate Cox regression analysis, high values of these variables were associated with adverse PFS (age-adjusted baseline OPG levels: hazard ratio (HR) 3.33, 95% confidence interval (CI) 1.24-8.94, p = 0.02; baseline ESR: HR 1.85, 95% CI 1.10-3.11, p = 0.02; post-NACT NLR: HR 1.89, 95% CI 1.08-3.31, p = 0.03). Of further note, patients' serum levels of RANK (TNFRSF11A) paralleled OPG alterations during the neoadjuvant therapy. Specifically, the CRT-induced changes in OPG and RANK were associated with PFS – the higher the increase (fold-change from NACT completion), the lower risk of a PFS event following definitive surgery (OPG: HR 0.27, 95% CI 0.09-0.87, p = 0.03; RANK: HR 0.13, 95% CI 0.02-0.76, p = 0.02). Correspondingly, by one-way analysis of variance, decline in serum levels during CRT (fold-change from NACT completion) was associated with adverse CTCAE grade diarrhea, the clinical correlate of treatment toxicity (OPG: p&lt;0.01; RANK: p&lt;0.01).
Conclusions: In this LARC study, elevated levels of systemic inflammation markers on commencement of neoadjuvant therapy were associated with adverse PFS. On the contrary, the association between strong increase in circulating TNFR proteins at CRT completion and favorable outcome in a patient population treated with curative intent but with metastatic disease as the main PFS event suggests that systemic antitumor immunity may be invoked by radiation.
Citation Format: Sebastian Meltzer, Erta Kalanxhi, Helga Helseth Hektoen, Svein Dueland, Kjersti Flatmark, Kathrine Røe Redalen, Anne Hansen Ree. Circulating tumor necrosis factor receptor (TNFR) proteins in systemic disease outcome to combined-modality radiotherapy in rectal cancer. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C101.