Am I going to lose my hair? That’s a question many cancer patients ask when they find out that they need radiation. I know that it would certainly be on my mind if I were in that situation.

Such treatment can save lives, but the hair loss that often accompanies it can be quite upsetting. True, compared with battling the cancer itself, losing hair is a relatively minor issue—but it’s one more source of distress at a time that’s already overwhelmingly stressful. So wouldn’t it be nice if that side effect could be avoided?

Maybe it can, an encouraging new study shows, simply by altering one minor aspect of treatment—the time of day when radiation is given. Here’s why…

SPLITTING HAIRS

Radiation kills cancer cells, but it also damages nearby healthy tissue, including hair follicles. When radiation is delivered to the head or neck area—to treat cancer of the brain, mouth, throat, thyroid, etc.—partial hair loss or total baldness can result. (With radiation, hair loss occurs only at the part of the body that is being treated. Chemotherapy, which wasn’t included in this study, can lead to hair loss all over the body.) Sometimes the hair eventually grows back…sometimes it doesn’t.

Researchers wondered whether the time of day at which radiation was given would affect the subsequent amount of hair loss. Why did they think there might be a connection? Because hair is constantly undergoing a complex cycle of growth and restoration that relies on circadian rhythm. (You probably think of circadian rhythm in terms of the 24-hour “master clock” in the brain that governs sleep and certain other biological functions. However, scientists now know that various tissues, including hair follicles, have their own “local” circadian clocks that orchestrate rhythms for their particular functions. The local clock for hair also operates on a 24-hour cycle.)

First, the researchers confirmed that there were many more mitotic cells (cells in the process of dividing and proliferating) within hair follicles in the morning…and that the mitotic cells decrease by 50% to 70% in the evening. As a consequence, hair grows faster in the morning…whereas in the evening, follicles are busy repairing whatever DNA damage was done during the growing time. Just think of a man’s beard—shaving in the morning leads to a 5:00 (pm) shadow in the early evening…but shaving in the evening does not lead to a 5:00 (am) shadow in the early morning.

During the mitotic phase of the cells’ cycle, hair is particularly vulnerable to damage from any sort of stress—and radiation is especially harmful because the extreme levels of energy damage the cells’ DNA (which is why it works on killing cancer cells). So researchers designed an experiment using mice to measure the effects of scheduling radiation at different times of day.

Fascinating findings: Radiation delivered at 9 am resulted in nearly bald mice, with 85% of their hair lost…but when the same amount of the same type of radiation was delivered at 5 pm, the mice kept most of their hair, with only 17% being lost! This same connection between radiation timing and the amount of hair lost was seen at all levels of radiation except for the very highest dose tested, where hair loss was extensive no matter what time of day it was given. (With human patients, radiation doses do vary depending on the type and severity of the cancer—but the doses used in this animal study corresponded to the dosage range used in humans.)

To confirm the connection, the researchers also did the experiment on mice that were circadian deficient (missing the master clock that sets the circadian rhythm). In those mice, hair loss was the same regardless of the time of day when radiation was given.

DOES IT WORK IN HUMANS?

The researchers theorize that, in the evening, when hair follicles are in the restoration part of the cycle, they are already primed to repair damage from normal sources and can more easily handle the additional stress from the radiation. Think of it this way: Adding one more wrinkled shirt to the pile isn’t a big deal when you’re already ironing the weekly laundry…but having to deal with a wrinkled shirt the next day, after the ironing board is put away, is a bigger hassle.

Cancer cells, which are constantly dividing, do not have circadian clocks. This means that altering the time of day at which radiation treatment is given would not make the therapy any less effective at combating the cancer.

We don’t yet know for sure whether scheduling radiation therapy for a certain time of day would reduce hair loss in humans—studies on people rather than animals are needed to explore that—but the researchers think that it’s likely. In fact, they suspect that other tissues with similar circadian cycles, such as bone marrow and the gastrointestinal tract lining, also might be spared from collateral damage if radiation therapy is timed appropriately.

The researchers stopped short of suggesting that cancer patients schedule their radiation appointments for late in the afternoon rather than first thing in the morning, citing the need for additional research. But in the meantime, I think that if I ever need radiation, I’ll aim for those afternoon sessions…and hope that the strategy would help me keep my hair during the battle against cancer.