The trillions of cells in the human body run to the rhythm of an ever-ticking clock. This internal timepiece is known as the circadian rhythm, where "circadian" stems from the Latin words "circa diem," meaning "around a day." In roughly 24-hour cycles, the functions of the body's tissues fluctuate, and throughout the day and night, these oscillations in activity affect everything from blood pressure levels and hormone production to immune cell activity and energy metabolism.
Evidence suggests that cancer also tunes its activity to the circadian rhythm and that our internal clock influences how the body breaks down and reacts to drugs. These observations raise an important question: Does it matter what time of day you get cancer treatment? For instance, is there an optimal time to get chemotherapy when the treatment would be the safest and most effective?
