82). These pathways from the hallmark gene sets included protein secretion, glycolysis, xenobiotic metabolism and haem metabolism (Ref. 82). These data highlight a general role for metabolism is dictating response to RT in RC. A more specific study in 2021 established pretreatment circulating levels of metabolic marker paraoxonase-1 was predictive of good response to neoadjuvant CRT in rectal cancer patients (n = 32) (Ref. 83). Conversely, low levels of systemic succinate were indicative or disease relapse in a cohort of 48 rectal cancer patients receiving NCRT (Ref. 83). This evidence concerns the gene PON1 and rectal cancer.