SUPERFICIAL RADIATION THERAPY
Superficial radiation therapy (SRT) relies on low-energy photon radiation.
SRT is a viable nonsurgical option for the treatment of select nonaggressive primary BCCs and SCCs in patients where surgical intervention is refused or inadvisable.
An understanding of basic radiobiology is a prerequisite for utilizing any form of radiation therapy.
The time–dose–fractionation (TDF) table provides a choice of protocols for a course of SRT based on the total dose of radiation, number of fractions, and duration of treatment.
Hyperfractionated dosing regimens may yield an improved outcome.
Ideally, radiation treatment for keloids should be administered within 2 days of surgical excision.
Various fractionation protocols may be used to accommodate the needs of each patient based on the size and location of the tumor, vascularity of the tissue, and the sensitivity of the tumor to radiation.
Protocol modifications may include reducing the fraction size, increasing the number of fractions and total radiation dose, and changing the overall duration of treatment from the first fraction to the last.
Modifying the size and number of the fractions and the total dose of administered radiation can prevent or minimize the occurrence of acute and latent radiation reactions while still optimizing the cure rate.
While there is no immediate scarring from SRT, significant long-term scarring is possible, especially over time.
Importantly, none of the recent SRT studies had a mean duration of follow-up greater than 5 years; therefore, long-term results should be viewed with caution.
Pitfalls and Cautions
Acute reactions are defined as adverse events occurring within 90 days of administration of the first dose fraction.
Latent reactions are defined as reactions occurring more than 90 days following the administration of the first fraction.
Dyspigmentation and telangiectasias are seen frequently, and unlike surgical scars, which tend to improve over time, long-term sequelae of SRT tend to worsen over years and decades.
Patient Education Points
While there is no surgical scar after SRT, it is not a scar-free procedure, and dyspigmentation, textural changes, and telangiectasias tend to increase over time.
Therefore, this approach should be used with extreme caution in younger patients.
Superficial radiation therapy (SRT) uses low-energy photon radiation that minimizes penetration beyond the thickness of the skin.1 Half of the energy is absorbed within the superficial layers of skin. On the electromagnetic spectrum, SRT waves are just above Grenz rays, low-energy or “ultrasoft” x-rays produced by 10 to 30 kV x-ray machines. Grenz rays have a half-value depth of 0.5 mm and are absorbed within the first 2 mm of skin tissue. ...