Image-Guided Superficial Radiation Therapy (IG-SRT) is an advanced, non-surgical approach designed for non-melanoma skin cancers, primarily basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). Unlike invasive surgical methods, IG-SRT uses low-energy X-rays to destroy cancer cells without the need for cutting, stitches, or anesthesia. The treatment combines traditional radiation therapy with real-time imaging. This method offers a comparable cure rate to surgery for early-stage non-melanoma skin cancers while prioritizing cosmetic results.
The Fundamentals of Image Guided SRT
Image-Guided Superficial Radiation Therapy is built upon the established principles of Superficial Radiation Therapy (SRT), which uses low-energy X-rays to treat cancer. These X-rays are carefully calibrated to penetrate only the top layers of the skin, typically just a few millimeters, where basal and squamous cell carcinomas are located. This shallow penetration ensures that the radiation dose is concentrated on the tumor, sparing underlying healthy tissue, muscle, and bone. The radiation works by damaging the DNA of the cancer cells, which prevents them from multiplying.
The “Image-Guided” component represents a significant technological advancement over older SRT methods. This guidance involves the use of high-resolution dermal ultrasound (HRDUS) imaging immediately before and often during each treatment session. The ultrasound allows the practitioner to visualize the tumor’s exact width, depth, and margins in real-time beneath the skin’s surface. This precise visualization ensures the radiation beam is perfectly aligned with the cancerous tissue, allowing for adaptive dosing and accurate tracking of tumor shrinkage. This capability minimizes the risk of missing cancerous tissue while ensuring the surrounding healthy skin receives the lowest radiation dose possible.
What Happens During an IG-SRT Session
The process of receiving IG-SRT begins with a consultation and a detailed simulation or planning phase. During this initial visit, the physician uses the high-resolution ultrasound to confirm the exact boundaries and depth of the cancerous lesion. Custom shielding, often made of lead, is created to protect the healthy tissue from the low-energy X-rays. This planning session establishes the precise treatment parameters for the entire course of therapy.
The daily treatment routine typically involves multiple short sessions, often scheduled three to five times per week, over a period of four to seven weeks. Each individual session is brief, usually lasting around 10 to 15 minutes. The patient is positioned comfortably, and the custom shield is placed over the treatment site, exposing only the area to be treated.
Immediately before the radiation is administered, the image guidance device, usually the ultrasound probe, is applied to the area. This step verifies the target’s position and allows the radiation therapist to confirm that the cancer’s depth and size align with the treatment plan. Once the alignment is confirmed, the radiation machine delivers the low-energy X-rays to the targeted area. Patients usually feel no pain, and some may only experience a slight sensation of warmth during the treatment delivery.
When IG-SRT is Recommended Over Surgery
The decision to recommend IG-SRT often comes down to balancing the patient’s individual health profile and the specific characteristics of the skin cancer. IG-SRT becomes a preferred option for patients who may be poor surgical candidates due to existing health conditions. This includes individuals on blood thinners, those with pacemakers, or older patients with significant comorbidities where the risks associated with surgery and anesthesia are elevated.
The location of the tumor is another primary factor that favors the non-surgical approach of IG-SRT. Lesions on cosmetically or functionally sensitive areas, such as the nose, eyelids, ears, lips, or scalp, are often better managed with radiation to preserve tissue and appearance. Since IG-SRT does not require cutting or stitches, it avoids the risk of scarring, disfigurement, or the need for complex reconstructive surgery.
This treatment is also suitable for large or ill-defined tumors where surgical excision might require the removal of a substantial amount of healthy tissue. Patients who have an aversion to surgery or wish to avoid the wound care and recovery time associated with surgical procedures may opt for IG-SRT. While Mohs surgery remains the standard for complex or aggressive skin cancers, IG-SRT offers a highly effective alternative for early-stage basal and squamous cell carcinomas.
Anticipating Recovery and Side Effects
Recovery from IG-SRT involves minimal downtime, and patients are generally able to continue their normal daily activities immediately after each session. Side effects are typically mild and localized to the treatment site, often beginning later in the treatment course and resolving within a few weeks of completion. The most common short-term effects include skin irritation, redness that resembles a sunburn, and temporary dryness or peeling.
Longer-term cosmetic outcomes are generally excellent, as the treatment avoids the visible scarring that can result from surgical removal. However, permanent changes within the treated field can include loss of hair and potential alterations in skin pigmentation, which may appear as lighter or darker patches. Patients must commit to long-term follow-up care to monitor the treated area and watch for any signs of recurrence, though the cure rates for IG-SRT are reported to be over 99% for non-melanoma skin cancers.