Circadian rhythms integrate many physiological pathways, helping organisms to align the timing of various internal processes to daily cycles in the external environment. Disrupted circadian rhythmicity is a prominent feature of modern society, and has been designated as a probable carcinogen. Here, we review multiple studies, in humans and animal models, that suggest a causal effect between circadian disruption and increased risk of cancer. We also discuss the complexity of this connection,

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... h may depend on the cellular context. signifi cance: Accumulating evidence points to an adverse effect of circadian disruption on cancer incidence and progression, indicating that time of day could infl uence the effectiveness of interventions targeting cancer prevention and management.