Skin cancer is the most frequently diagnosed cancer globally, resulting from the uncontrolled growth of abnormal cells in the outer layer of the skin. Treatment plans are highly individualized, often involving surgery as the primary approach for localized disease. Radiation therapy (RT) uses high-energy particles or waves to damage the DNA of cancer cells, preventing them from dividing and growing. This treatment is utilized for curative intent, preventing recurrence after surgery, or providing symptom relief. The decision to incorporate radiation depends on the cancer type, location, disease stage, and the patient’s overall health.
Radiation as Primary Treatment for Non-Melanoma Skin Cancer
Radiation therapy is frequently used as a definitive, stand-alone treatment for Basal Cell Carcinoma (BCC) and Squamous Cell Carcinoma (SCC), the two most common forms of skin cancer. This non-surgical option is preferred when surgery is impractical or carries a high risk of complications, such as for elderly patients or those with multiple comorbidities who are not suitable candidates for general anesthesia.
Radiation is also beneficial for lesions in anatomically sensitive locations, such as the eyelid, nose, ear, or lips, where surgical removal might cause significant disfigurement or loss of function. It can also treat very large tumors where surgical excision would require extensive reconstruction.
The goal is to deliver a precise dose of radiation directly to the tumor, destroying cancer cells while minimizing damage to surrounding healthy tissue. While surgery remains the standard for most early-stage non-melanoma skin cancers, radiation offers a comparable cure rate for appropriately selected superficial lesions.
The Role of Radiation in Treating Melanoma
Radiation therapy is rarely employed as the primary treatment for typical cutaneous melanoma because these cancer cells are often radioresistant. The primary curative approach remains surgical excision. Radiation’s role is largely adjunctive (used in addition to surgery) or palliative (focused on quality of life).
Adjuvant radiation is delivered after surgery to target microscopic cancer cells remaining in the area, reducing the risk of local recurrence. This is recommended for patients whose melanoma exhibits high-risk features, such as deep invasion, ulceration, or spread to the lymph nodes. Desmoplastic melanoma, which tends to recur locally and invade nerves, is commonly treated with adjuvant radiation following surgery.
For advanced or metastatic melanoma, radiation therapy is highly effective for palliation, relieving symptoms caused by the cancer’s spread. A short course of high-dose radiation can reduce pain from bone metastases or alleviate neurological symptoms caused by brain metastases. In these settings, treatment focuses on rapidly improving the patient’s comfort rather than achieving a cure.
Cancers Where Radiation is a Standard and Necessary Component
Certain types of skin cancer or advanced disease presentations require radiation therapy as a mandatory component of the overall treatment strategy. Merkel Cell Carcinoma (MCC), a rare but highly aggressive neuroendocrine skin cancer, is a prime example. MCC has a high propensity for both local recurrence and spreading to nearby lymph nodes and distant organs, even after the primary tumor is successfully removed by surgery.
For MCC, radiation is routinely administered to the primary tumor site and the draining lymph node basin, often following surgery, to eliminate residual microscopic disease. Studies have shown that patients treated with surgery followed by radiation have better local control rates than those treated with surgery alone. If the tumor is too large or the patient is medically unfit for an operation, radiation can be used as a definitive, stand-alone treatment for MCC.
Advanced non-melanoma skin cancers like SCC or BCC also require post-operative radiation when specific high-risk features are identified in the surgical specimen. One feature is perineural invasion, where cancer cells track along a nerve sheath, indicating a higher risk of recurrence. When cancer cells cannot be entirely removed because the tumor is invading deep structures or is unresectable, radiation is necessary to maximize disease eradication.
How Radiation Therapy is Delivered
Once the decision is made to use radiation, a precise planning process called simulation is undertaken to accurately map the treatment area and determine the optimal dose. The delivery method is chosen based on the tumor’s depth and location.
Superficial Radiation Therapy (SRT) uses low-energy X-rays that penetrate only a short distance, making it ideal for skin-surface tumors like early BCC and SCC while sparing deeper tissues. External Beam Radiation Therapy (EBRT) utilizes a linear accelerator to direct high-energy beams at the tumor from outside the body. EBRT is used for deeper or larger tumors, including advanced non-melanoma cancers and lymph node basins in MCC and melanoma.
Another technique, brachytherapy, involves placing a radioactive source directly on or within the tumor. This allows for a very high, localized dose while minimizing exposure to surrounding healthy tissue. The typical treatment schedule for curative intent involves daily sessions, usually five days a week, over several weeks. This fractionation approach allows healthy tissues to repair themselves between treatments while the cancer cells are destroyed.