Chronotherapy, Circadian Rhythms and Cancer
Questions from the Clinic:
What is cancer chronotherapy? Do circadian rhythms influence the efficacy of cancer drugs? Can other procedures, like radiotherapy, be timed to optimize their effect?
I. Introduction
Over decades of research, scientists have observed that patients with cancer vary considerably in the degree to which they respond to treatment. Although genetic differences can explain this phenomenon to some degree, emerging evidence indicates that other factors influence the efficacy of therapies.(1) In particular, accumulating data across multiple studies show that the majority of today’s best-selling drugs work better when taken during specific times of the day.(2) Accounting for the circadian clock (i.e., circadian rhythms) and targeting its underlying mechanisms form the basis of cancer chronotherapy. When paired with radiation, chemotherapy, and immunotherapy, chronotherapy may enhance therapeutic efficacy and simultaneously minimize treatment-related adverse events associated with medical interventions.(3) Despite these benefits, fewer than 1% of investigators running clinical trials incorporate time-of-day considerations into their study protocols.(4) Low clinical awareness and adoption may, in part, stem from mixed results from human trials examining the benefits of chronotherapy in cancer treatment.(5) Resolving these inconsistent findings is critical, as a better appreciation and understanding of biological chronicity may be key in further individualizing cancer medicine and optimizing patient outcomes for years to come.(1)