SP5.10 - Statin use during neoadjuvant therapy is an independent marker for a favourable Neoadjuvant Rectal (NAR) score in locally advanced rectal cancer when analysing common concomitant medications

Abstract Aim The extent of neoadjuvant therapy (NAT) response is an important prognosticator in locally advanced rectal cancer (LARC). The Neoadjuvant Rectal (NAR) is validated as a pseudo-continuous measurement of response, and a surrogate marker of long-term outcomes. We investigated the impact of common concomitant medications (statins, antiplatelets, metformin) on the extent of response using the NAR score. Methods A retrospective review of regional cancer centre LARC patients undergoing NAT was performed between June 2016 - 2021. The NAR score was calculated as previously described by George et al (2015). Results 253 patients were included. 104(34%), 52(17%), and 19(6%) patients took statins, antiplatelets, and metformin respectively. 90% of those on an antiplatelet are also on a statin. Of those on statins, 45.2% and 14.4% also took antiplatelets or metformin respectively. There was no significant association with concomitant medication use and disease stage or tumour size. Only metformin use associated with the absence of Extramural vascular invasion (EMVI) (p=0.031) on pre-NAT MRI. Neither antiplatelets nor metformin use associated with the extent of NAT response. Statin use associated with a favourable NAR score (p=0.008). On multivariate analysis with pre-NAT mrEMVI and nodal status, concomitant statin use independently predicted a favourable NAR score of <16 (OR 2.019, 95%CI 1.11-3.67, p=0.021). Conclusion Concomitant statin use at time of neoadjuvant therapy associates with a favourable response. Antiplatelet and metformin use does not appear to influence response. Analysis through a clinical trial of statin use combined with neoadjuvant therapy may give more insight into how it influences response.