Research on radiotherapy at different times of the day for inoperable cervical cancer

To investigate the radiation effects and acute damage in inoperable cervical cancer patients irradiated at different times as well as the underlying mechanisms.

67 patients were randomized to a morning group (MG, 9:00 - 11:00 AM) and an evening group (EG, 9:00 - 11:00 PM) and both received external beam radiotherapy (RT) (50 Gy in 25 fractions) at different times. Brachytherapy (36 - 42 Gy in 6 - 7 fractions) was also performed to enhance the radiation response twice every week in all patients at the same time. Clinical therapeutic effects and acute toxicities were evaluated after RT. Flow cytometry was analyzed before and after RT.

Patients' response to radiation was similar in the two groups. Incidences of overall and high-grade (III - IV) diarrhea in the MG vs. the EG were 75.0% vs. 57.6% and 12.5% vs. 6.1%, respectively. The incidence of severe hematological toxicity in the EG was significantly increased compared to the MG group. Cell apoptosis in the EG was significantly higher at 9:00 - 11:00 PM than that at 9:00 - 11:00 AM after RT. No significant differences were found in Gap Phase 0/Gap Phase 1 (G0/G1), Gap Phase 2/Metaphase Phase (G2/M), and Synthesis Phase (S) phase between different times and groups, nor were expressions of Per1, Per2, and Clock. But expressions of Per1, Per2, and Clock were significantly negative with G2/M phase and positively correlated with cell apoptosis.

RT at different time intervals results in similar efficacy. However, RT in the morning reduces severe hematological toxicity. Radiation responses may be associated with circadian genes by influence of cell cycles and apoptosis.
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