Afternoon/Evening Radiation Boosts Cancer Treatment Efficacy

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A new study has found that the human body's internal circadian clock influences the effectiveness of radiation therapy for cancer treatment. Researchers discovered that DNA repair mechanisms peak in the early morning and decline throughout the day, reaching their lowest point in the evening. This fluctuation is governed by a protein called CRY1, a core component of the circadian clock. When CRY1 levels are low, typically in the afternoon or evening, DNA repair slows down, making cancer cells more vulnerable to radiation. This has led to the concept of 'chronoradiotherapy' - tailoring radiation treatment schedules to coincide with periods of reduced DNA repair, which could significantly enhance the effectiveness of radiation therapy.

Why it matters

This discovery opens the door to a more personalized approach to cancer treatment, where radiation schedules are optimized based on an individual's biological clock and the specific characteristics of their tumor. This could potentially lead to higher cure rates, reduced side effects, and improved quality of life for cancer patients. The research also highlights the importance of understanding the complex interplay between our internal biological rhythms and disease progression.

The details

Researchers at the Andalusian Centre for Molecular Biology and Regenerative Medicine (CABIMER) and the University of Seville found that DNA repair activity peaks in the early morning and gradually declines throughout the day, reaching its lowest point in the evening. This fluctuation is governed by the protein CRY1, a core component of the circadian clock. When CRY1 levels are low, typically in the afternoon or evening, DNA repair slows down, making cancer cells more vulnerable to radiation. Retrospective analysis of patient data supports this theory, with patients with breast cancer and prostate cancer exhibiting increased sensitivity to radiation therapy when treated during the afternoon or evening.

• The study was published in Nature Communications in 2026.
• Researchers analyzed patient data to observe the effects of timing radiation therapy.

What’s next

Further research is needed to understand why some cancers are more susceptible to chronoradiotherapy than others. Identifying biomarkers – like CRY1 levels – that predict a patient's response to time-based radiation scheduling could personalize treatment plans and improve outcomes.