The Time of Day Cancer Patients Get Chemotherapy May Be Significant: Study

The battle against cancerous tumors may be more effective if waged at night, an Israeli medical study suggests.

Researchers at the Weizmann Institute of Science found that tumors grew more quickly at night in the mice they examined, offering the possibility that chemotherapy and other therapies may be more effective based on the time of day they are administered.

“It could mean that some treatments should be done during the night,” study co-author Yehoshua Enuka told the Media Line, an Israeli news service. “It could also lead to a better understanding of the exact biological and molecular mechanism that governs the process of tumor progression.”

Photo: Shutterstock/Brian A Jackson

The study was performed on laboratory mice, looking specifically at gastric tumors. Unlike humans, the mice were more active at night and slept during the day, when the tumors grew at a more rapid rate.

Don Katcoff of the Faculty of Life Sciences at Bar Ilan University told the Media Line, “They found that the tumors became smaller if chemotherapy was given to the mice during the daytime, which is equivalent to our night,” adding that the difference was “statistically significant.”

Researchers have previously examined the relationship between the time of day one sleeps and cancer growth. A 2005 study of mice showed that exposing mice with cancer to artificial light stimulated the growth of breast tumors by suppressing melatonin. Extended periods of nighttime darkness slowed the growth of the tumors, according to the study, offering a possible explanation as to why female night shift workers had a higher rate of breast cancer, the National Institutes of Health reported.

The new study found that treatment administered at night was more effective, because the steroid hormone glucocorticoid is low “during the resting phase of the day.”

“These findings support a circadian clock-based paradigm in cancer therapy,” asserted the study which was published in Nature Communications.

“If we know it progresses more at night, we know there are different biological mechanisms that are more prevalent during the night. The cortisol seems to block the biological processes that enhance the tumor,” said Enuka, the study co-author.