J. C. Kong1,2, G. R. Guerra1,2, R. M. Millen1,2, S. K. Warrier1,2, W. Phillips1,2, A. C. Lynch1,2, R. Ramsay1,2, A. G. Heriot1,2 1Peter MacCallum Cancer Centre,Division Of Cancer Surgery,Melbourne, VIC, Australia 2The University Of Melbourne,Sir Peter MacCallum Department Oncology,Melbourne, VIC, Australia
Introduction
Currently there are no reliable methods that can adequately predict response to neoadjuvant chemoradiotherapy (NACRT) in locally advanced rectal cancer. However tumour infiltrating lymphocytes (TIL) have gained significant prominence in predicting response and survival outcome in rectal cancer. The aim of this study was to assess whether a novel functional cytotoxic immune assay measuring the kinetics of TIL killing predicts pathological tumour response after NACRT accurately.
Methods
Treatment naïve fresh rectal cancer biopsies from each patient was processed to cultivate organoids and TIL. An immune cytotoxic assay comprising of patient-matched TIL and organoids were co-cultured for 48 hours. A fluorescence microscope was utilitised to measure organoid death, by an automated computer algorithm that calculates the mean fluorescence intensity.
Results
A total of 17 consecutive rectal cancer patients were recruited. In each cytotoxic assay, a total of 15,000 organoids were measured, with organoid to TIL ratio of 1:10,000. The mean fluorescence intensity for each response group were; complete response=27982 (n=6), partial response=16663 (n=5) and no response=8933 (n=6) (p-value<0.001). This demonstrates that by measuring the kinetics of TIL killing, it can predict response to NACRT accurately before surgery. This was further validated by measuring the IFN-Y production of cytotoxic (CD8+) T cell, which was significantly higher in complete/partial response TIL compared to no response TIL (mean 1969 pg/ml and 76 pg/ml respectively, p-value=0.02).
Conclusion
A functional immune assay can predict rectal cancer response to NACRT. This has the potential both to modify clinical management and opens the door for novel therapeutic approaches.