Topical agents do not increase radiation dose during cancer radiotherapy

Topical skin treatments do not increase radiation dose to the skin during radiotherapy and, therefore, can be used by individuals with cancer prior to radiation treatments, according to study results.

The finding debunks a longstanding myth, according to Brian Baumann, MD, assistant professor of radiation oncology at Washington University School of Medicine in St. Louis and adjunct assistant professor at University of Pennsylvania’s Perelman School of Medicine, Ioannis Verginadis, PhD, research associate in the department of radiation oncology at Perelman School of Medicine, and colleagues.

Nearly two-thirds of patients with cancer undergo radiation, and up to 90% of them will experience radiation dermatitis.

These patients often use prescription or over-the-counter topical treatments for relief; however, patients traditionally have been told to avoid these agents due to concerns that they would increase the amount of radiation absorbed by the skin.

Baumann, Verginadis and colleagues conducted a three-part study to assess the effects of these topical agents during radiation.

In the first part, researchers surveyed clinicians and patients. Of the 105 clinicians who responded, 96 indicated they had been advising patients against using skin lotions or creams prior to radiation treatment. Of the 133 patients who responded, 111 said they had been told by their physicians or nurses to avoid using topical ointments before undergoing radiation.

In the second part of the study, researchers applied radiation to squares of paper bearing lotions of varying thicknesses and used optically stimulated luminescent dosimeters to measure absorbed surface radiation. Results showed increases in surface radiation absorption for extremely thick layers of creams but no increase for moderately thick applications, which most patients would apply.

For the third part of the study, researchers applied creams of varying thicknesses to the skin of mice before radiation. Again, researchers observed no additional radiation absorption caused by the topical creams.

HemOnc Today spoke with Verginadis about the study and the potential implications of the results.

Question: Can you provide some background on the long-held belief that patients should not use creams or lotions while receiving radiotherapy ?

Answer: The traditional thinking has been that applying topical agents just before radiotherapy would increase radiation dose to the skin and the risk for skin toxicity. Patients were instructed to avoid applying topical agents for at least a few hours before radiation treatments to avoid this risk. This recommendation became widespread by the 1950s, when lower-energy radiation beams — which tend to deposit more dose to the skin — were used. With modern, higher-energy, megavoltage radiation — which delivers less dose to the skin — the recommendation to avoid topical agents just prior to radiation may no longer be warranted.

Q: Can you summarize your findings?

A: We think the practice of doctors advising patients not to use topical creams prior to radiation is not based on scientific data. There was no increase in the surface dose in the presence or absence of skin creams, except in the case of very thickly applied creams, much thicker than patients applied in the clinic. The use of topical agents, even if applied just prior to radiotherapy, can now be liberalized, which may improve patient quality of life.

Q: Did the results surprise you?

A: Yes. Based on what we knew and thought, we believed when we studied the effects on a very thick layer of cream that there would be more of an increase in the surface dose than what we observed.

Q: Do you believe that physicians should start recommending that patients can apply these lotions and creams prior to undergoing radiation ?

A: The results do show that thin or moderately thick applications of topical cream, even if applied just prior to radiation, are safe and do not increase the skin dose. We think these results are practice-changing and should improve patient quality of life. – by Scott Buzby

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Original Date: Jan 3 2019

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