30 January 2023

Researchers have found that female cancer patients might derive greater benefit from receiving chemotherapy in the afternoon rather than the morning, though these results need to be verified in large scale clinical trials.

Professor Koh Youngil of Seoul National University Hospital, South Korea, and colleagues investigated the impact of timing on chemotherapy, as part of an approach called ‘chronochemotherapy’.

The idea is to deliver a drug at a timepoint during the day when the body is least vulnerable to harmful side-effects and cancer cells are at their most vulnerable.

The team retrospectively analysed the outcomes of 210 patients with diffuse large B-cell lymphoma (DLBCL), being treated with R-CHOP. Patients received their chemotherapy at either 8.30am or 2.30pm.

Analysis showed that female patients who were treated in the afternoon had 12.5-times reduced mortality rate – 2% versus 25% – compared with those treated in the morning. The afternoon group also showed a 2.8-times lower cancer recurrence rate at 60 months – 13% versus 37%. No similar effect was seen in male patients.

Females treated in the afternoon also experienced fewer side-effects including neutropenia. Findings were published in JCI Insight recently.

To understand what might be causing the effect, the researchers tested 14,000 blood samples from a large hospital. This showed that in females, white blood cell counts fall in the morning and increase in the afternoon. Because there is a 12-hour delay between bone marrow proliferation and blood cell production, this indicates that bone marrow proliferation rate is higher in the morning.

Hence, the researchers speculate that afternoon chemotherapy is preferable because the bone marrow is producing fewer blood cells. Male patients do not show as wide a variation throughout the day.

Professor Young-il said: “We plan to verify the conclusions of this study again with a large-scale follow-up study.”



Kim DW, Byun JM, Lee JO, Kim JK, Koh Y. (2023) “Chemotherapy delivery time affects treatment outcomes of female patients with diffuse large B-cell lymphoma.” JCI Insight, doi: 10.1172/jci.insight.164767

Link: https://insight.jci.org/articles/view/164767

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