Abstract 4531: SWATH-MS profiling identifies prognostic factors for progression-free survival (PFS) In INTEGRATE - A randomized phase II double-blind placebo-controlled study of regorafenib in refractory advanced oesophagogastric cancer (AOGC) - A study by the Australasian Gastrointestinal Trials Group (AGITG)
Authors: Hayes Sarah A. , Martin Andrew , Yip Sonia , Howell Viive M. , Sjoquist Katrin M. , Tsobanis Eric , Kang Yoon-Koo , Bang Yung-Jue , Alcindor Thierry , O'Callaghan Christopher J. , Tebbutt Niall C. , Simes John , Goldstein David , Pavlakis Nick 
Published: August 2019

Introduction: Gastric cancer is one of the most common cancers worldwide, and a leading cause of cancer death. Advanced OesophagoGastric cancer (AOGC) has a poor prognosis despite treatment. The P2 INTEGRATE multinational 2:1 (active:placebo) randomized trial demonstrated the activity, on progression-free survival (PFS), of the oral multikinase inhibitor regorafenib (REG) in patients (pts) with refractory AOGC (Pavlakis et al JCO 2016), leading to the P3 INTEGRATE II trial (NCT02773524) currently underway. Here, we sought to identify prognostic protein biomarkers in a discovery analysis of a patient subset from INTEGRATE I.

Methods: The discovery analysis set comprised of 40 INTEGRATE I patients (12 placebo; 28 REG) selected using stratified random sampling based on quartiles of observed PFS within each arm of allocation, half from 1st quartile (worst PFS outcome) and half from 4th quartile (best PFS outcome). We profiled the plasma proteome of INTEGRATE pts using data-independent acquisition of liquid chromatography coupled with tandem mass spectrometry (SWATH-MS acquisition). Plasma collected at baseline (10µl) was analyzed with TripleTOF 6600 System (SCIEX, MA, USA). Data was searched against an “extended” spectral library generated using SwathXtendsoftware (Wu et al MCP 2016). Cox proportional hazard regression was used to assess the prognostic value of log2 protein expression level adjusted for treatment allocation.

Results: 437 proteins were identified across all 40 pt samples (&gt;99% peptide confidence). A subset of 27 proteins were identified as candidates for possible further investigation using the verification analysis set on the basis of having p-values &lt;0.05 (no p-value was significant after adjustment for multiple comparisons). These proteins were associated with (i) the immune system, including multiple immunoglobulin variable heavy and light chains, and proteins involved in complement activation (C09, C08G, C4BPA and C05 and others) and two serpins that regulate the acute phase response and promote cancer cell survival (AACT and A1AT); (ii) blood coagulation and angiogenesis (THBS1/PROS1/FBLN1 and others), also instrumental in tumor progression. Other proteins are known to promote local cancer cell adhesion, invasion and distant metastasis.

Conclusions: This is the first time that SWATH has been used to analyse AOGC pt samples, an otherwise challenging biofluid (undepleted plasma) for profiling. These proteins could represent a novel prognostic signature for PFS in AOGC patients, pending validation in the larger verification data set. This work highlights the potential value of incorporating proteomics into risk assessments guiding treatment strategies for patients.

Citation Format: Sarah A. Hayes, Andrew Martin, Sonia Yip, Viive M. Howell, Katrin M. Sjoquist, Eric Tsobanis, Yoon-Koo Kang, Yung-Jue Bang, Thierry Alcindor, Christopher J. O'Callaghan, Niall C. Tebbutt, John Simes, David Goldstein, Nick Pavlakis. SWATH-MS profiling identifies prognostic factors for progression-free survival (PFS) In INTEGRATE - A randomized phase II double-blind placebo-controlled study of regorafenib in refractory advanced oesophagogastric cancer (AOGC) - A study by the Australasian Gastrointestinal Trials Group (AGITG) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4531.