Validation of the prognostic impact of lymphocyte infiltration (LI) in patients (pts) with stage III colon cancer (CC) treated with adjuvant FOLFOX+/- cetuximab: A PETACC8 translational study

Background: The prognostic value of LI of CC has been demonstrated by several groups. However no validated test is available for clinical practice. We previously described an automated and reproducible method for testing LI (Allard MA et al 2012) and aimed to validate it for clinical use. Methods: According to NIH criteria, we designed a prospective analysis of this biomarker in pts included in the PETACC8 phase III study. Primary objective was to compare % of pts without recurrence at 2 years in pts with high versus low LI (#NCT02364024). Secondary objectives were comparison of disease free (DFS) and overall (OS) survivals, and prognostic value of LI on these endpoints. Automated testing of LI was performed on virtual slides without access to clinical data. Results: Among the 1,220 CC pts enrolled, LI was high, low and not evaluable in 241 (20%), 790 (65%) and 189 (15%), respectively. High and low LI groups did not differ except for treatment arm (p=0.04) and microsatellite status (MSI/MSS) status (p=0.04). Primary objective was met with a 2-year recurrence rate of 14.4% versus 21.1% in pts with high and low LI respectively (p=0.02). Pts with high LI also had better DFS and OS (table). Stage, grade, KRAS status and LI were the only prognostic markers in multivariate analysis. Sub-group analyses revealed that high LI had better DFS and OS in MSS pts, and in pts without KRAS codon 12-13 mutation, but not in MSI neither in KRAS mutated pts. Conclusions: This is the first prospective validation of a LI testing in pts with stage III CC treated with FOLFOX adjuvant. Automated testing of LI also had a prognostic value for DFS and OS. Funding: Merck-Serono, Sanofi, Région Ile de France. Clinical trial information: NCT02364024.