Question

Please explain the rationale behind circadian timing of chemotherapy for cancer treatment

Answer 1

Periodic processes are responsible to regulate biochemical and physiological behaviors. Many important biological chemical signals can be released as pulses where the signal duration is brief compared to the elicited behavior. In cancer, circadian processes are responsible to influence the molecular and cellular mechanisms regulating mitosis and programmed cell death. Cells do not enter or exit the various cell cycle phases randomly throughout the day, but rather they can do in a highly organized fashion at the distinct circadian phases. Rhythmic coordination of tissue function can explain the circadian variation in sensitivity of rapidly proliferating tissues to the cytotoxic effects of chemotherapy. A relationship between the circadian drug timing and anticancer efficacy has been established. The cytotoxic drug toxicity can be diminished and both dose intensity and objective tumor response frequency can be increased and cancer patient survival improved by optimal circadian drug timing. In addition, cytotoxic drugs kill cells more or less effectively that depending upon the cell cycle phase. For that reason, circadian timing of chemotherapy for cancer treatment is very crucial.