Exercise timing and cancer treatment: Avenues for chronobiological research

Emerging evidence suggests that cancer chronotherapy, which involves timing drug administration in accordance with a patient's circadian/internal time, can improve treatment tolerability and efficacy. However, as cancer, its treatments, and even hospitalization can cause circadian rhythm misalignment, cancer chronotherapy may be attenuated from the start. The adjunctive therapeutic strategy 'exercise' not only improves physical function and patient-reported outcomes, but specific effects are determined by the individual's internal time and it may act as a circadian time cue. Utilizing differentially timed exercise in terms of targeting time-specific homeostatic responses to the activity, accounting for the time of peak performance, and/or targeting potential circadian system effects of exercise could thus potentiate cancer chronotherapy or cancer treatment more generally. Herein, we briefly overview cancer chronotherapy and exercise medicine in oncology, highlight potential benefit of timed exercise in cancer treatment, and discuss research opportunities to assess these potentials benefits.