Superficial Radiation Therapy (SRT) is a non-surgical treatment using low-energy X-rays, primarily for conditions affecting the skin’s surface. This specialized approach focuses therapeutic energy on the outermost layers of tissue. By precisely targeting surface abnormalities, SRT minimizes the impact on surrounding healthy tissues and underlying organs. Delivered in an outpatient setting, SRT is often an alternative to surgery for accessible skin lesions.
The Mechanism of Superficial Targeting
The fundamental difference between Superficial Radiation Therapy and conventional radiation lies in the energy level and depth of tissue penetration. SRT utilizes low-energy X-rays (50 to 150 kilovoltage peak), which are significantly weaker than megavoltage beams used for deep-seated tumors. This ensures the radiation dose is deposited almost entirely within the first few millimeters of the skin’s surface, typically limited to 2 to 7 millimeters.
The radiation works by introducing double-strand breaks into the DNA of targeted cells, especially rapidly dividing cancer cells. The energy falls off rapidly, effectively targeting abnormal cells in the epidermis and superficial dermis while sparing deeper structures like muscle, bone, and organs.
Advanced systems like Image-Guided SRT (IG-SRT) use high-resolution ultrasound to map the lesion’s precise depth and dimensions. This technique ensures the radiation dose is perfectly matched to the tumor volume, allowing for millimeter accuracy.
Conditions Effectively Treated
SRT is predominantly used to treat non-melanoma skin cancers, including Basal Cell Carcinoma (BCC) and Squamous Cell Carcinoma (SCC). Since these common cancers originate in the outer layers of the skin, they are ideal targets for SRT’s shallow penetration. For early-stage tumors, clinical results show high success rates, often exceeding 95%.
The non-surgical nature of SRT makes it suitable for lesions located in cosmetically sensitive areas, such as the face, nose, ears, and eyelids. It is often preferred for patients who are poor surgical candidates, such as those on blood thinners, or for those wishing to avoid an invasive procedure. SRT can also treat certain benign dermatological conditions, including preventing recurrent keloid scars after surgical removal.
What Happens During Treatment
Superficial Radiation Therapy is delivered through fractionation, involving multiple, small doses of radiation. Patients typically undergo short treatment sessions three to five times per week, spanning several weeks. The specific number of sessions depends on the size and type of the lesion.
During each session, the patient is positioned comfortably, and a specialized device delivers the low-energy X-rays directly to the treatment area. Protective shielding ensures only the targeted lesion receives the radiation dose. The treatment is painless, perhaps causing a slight warmth, and lasts only a few minutes. Since it is an outpatient procedure, there is no required downtime, allowing patients to resume normal daily activities immediately.
Recovery and Managing Skin Reactions
Following SRT treatments, the skin reacts to the cumulative radiation dose, but side effects are localized and temporary. Patients commonly experience reactions similar to a mild sunburn, including redness, dryness, and irritation, starting about ten days after the first session. Other reactions may include temporary hair loss or skin peeling within the treatment field.
Managing skin reactions involves supportive care. Patients should use gentle, non-irritating cleansers and apply moisturizers or prescribed creams to soothe dryness. Protecting the treated area from sun exposure is advised throughout the treatment course and afterward, using protective clothing and broad-spectrum sunscreen. These temporary side effects resolve within two to six weeks after the final session, often healing with minimal or no visible scarring.