Up to 90% of patients undergoing radiation therapy for cancer experience radiation dermatitis. While the symptoms are mild or moderate for many patients, some experience severe dermatitis that can cause not only substantial discomfort but also infection. Treatment involves topical ointments, but patients are often advised to avoid these ointments for several hours before daily radiotherapy because of concern that they might increase the radiation dose to the skin. In a recent study, researchers at the Perelman School of Medicine at the University of Pennsylvania found that this precaution is unnecessary: moderate amounts of topical creams do not affect the radiation skin dose.
In their study, published in JAMA Oncology, the researchers note that the recommendation against topical agents became widespread during the days of orthovoltage radiation, which ended in the early 1950s. "This recommendation is a holdover from the early days of radiation therapy, but with the use of modern radiation treatments that can reduce dose to the skin, we hypothesized that it may no longer be relevant," commented the study's lead author, Brian C. Baumann, MD, Adjunct Assistant Professor of Radiation Oncology at the Perelman School of Medicine and Assistant Professor of Radiation Oncology at Washington University in St. Louis.
The researchers found that in a survey of 133 patients who had received radiotherapy and 105 clinicians involved in managing patient skin care during radiotherapy, 83.4% of patients had been advised to avoid applying topical ointments prior to radiotherapy, and 91.4% of clinicians reported giving this advice. "These results suggest the recommendation is still widespread among patients undergoing radiation therapy," stated Dr. Baumann.
To investigate whether avoiding skin ointments prior to radiotherapy was necessary, the researchers measured radiation dosage to the skin using optically stimulated luminescent dosimeters (OSLDs). They found that a topical ointment application of 1- to 2-mm thickness prior to radiotherapy produced no difference in the dose of radiation delivered using en face 6- or 15-megavoltage (MV) photons either at the surface or 2 cm below the skin. The same amount of topical ointment had no effect at any beam incident angle from 15° to 60°, with the exception of a 6% increase at 60° when silver sulfadiazine cream—which contains heavy metals—had been applied.
With a topical ointment application of 3 mm or more in thickness, however, surface doses increased significantly. For the 6-MV beam, surface dosage was 1.05 Gy—grays, a unit of ionizing radiation dose—for petroleum-based ointment and 1.02 Gy for silver sulfadiazine cream, compared to 0.88 Gy without topical ointment. For the 15-MV beam, surface doses were also increased with thick topical application, with 0.70 Gy for petroleum-based ointment and 0.60 Gy for silver sulfadiazine cream, compared to 0.52 Gy without ointment. There were no dosage differences at a depth of 2 cm.
According to Dr. Baumann, the results indicate that "the use of topical agents just before radiation therapy can be safely liberalized, which may improve quality of life for patients undergoing radiation therapy, but very thick applications of topical agents just before radiation therapy should still be avoided."
For More Information
Baumann BC, Verginadis II, Zeng C, et al (2018). Assessing the validity of clinician advice that patients avoid use of topical agents before daily radiotherapy treatments. JAMA Oncol. [Epub ahead of print] DOI:10.1001/jamaoncol.2018.4292