A review of the literature, including published guidelines, and site visits to radiation oncology suites was undertaken to provide clinicians with background on indications, outcomes and practical considerations for selecting radiation therapy for the treatment of nonmelanoma skin cancers.
However, radiation is generally reserved as a primary therapy for patients who are not surgical candidates. In addition, one of the main considerations when evaluating radiation therapy against other possible treatment options is that it involves a protracted course of treatment, which typically includes 15 to 30 radiation sessions over several weeks.
"According to some reports, use of radiation therapy for skin cancer treatment has been decreasing, and younger physicians may be particularly unfamiliar with this option," says Aerlyn G. Dawn, M.D., M.B.A., resident, department of dermatology, University of Pennsylvania.
Information on radiation therapy for NMSC was derived from review of the National Comprehensive Cancer Network (NCCN) guidelines, published articles identified in a literature search, and first-hand site visits to radiation oncology suites.
According to the NCCN guidelines, radiation therapy is recommended for consideration as a primary treatment modality for basal cell and squamous cell carcinomas of the head and neck in patients over age 60 who are not surgical candidates, and as adjuvant therapy for high-risk tumors.
"Interestingly, the guidelines also stated that the role of radiation therapy for NMSC was the 'single largest source of disagreement among the NCCN panel of experts,' which may reflect the variation in treatment protocols and paucity of related evidence-based literature," Dr. Dawn tells Dermatology Times.
Collaborating physicians included Niraj H. Pahlajani, M.D., resident, department of radiation oncology, Fox Chase Cancer Center; Harry Quon, M.D., assistant professor of radiation oncology, and Christopher J. Miller, M.D., assistant professor of dermatology.
Electron beam radiation
Dr. Dawn says he was particularly surprised to find that electron beam radiation therapy has largely replaced low energy X-ray techniques as the primary mode of treatment at many academic centers.
"Even older dermatologists who are more likely to have some knowledge about radiation therapy would probably be surprised to learn that superficial and orthovoltage X-rays are no longer available at many tertiary care centers," Dr. Dawn says.
The NCCN guidelines also recommend margins for radiation therapy (5 mm to 10 mm for tumors less than 20 mm and 15 mm to 20 mm for larger lesions), although specific decisions about treatment fields also take into account tumor depth, certainty about tumor borders, and whether there is perineural invasion or lymph node involvement.
Radiation therapy sessions
Recommended fractionation schemes typically range from 15 to 30.
"The radiation therapy sessions are usually scheduled daily during the week, and so a typical regimen can take three to six weeks to complete.
"Dividing the total dose into more fractions is desirable to improve cosmesis, but if the daily visits are a hardship for the patient, consideration may be given to administering the total prescribed radiation dose in fewer fractions, although this increases the likelihood of adverse effects," Dr. Dawn says.
For small tumors (less than 2 cm) located on the eyelids, ears and nose, five-year local control rates of greater than 90 percent have been reported.
Local side effects are common as acute reactions to the treatment, and long-term, skin exposed to radiation therapy can become atrophied, scarred and show hyperpigmentation, hair loss and telangiectasias.
There is also a risk for non-healing ulcers to develop and, rarely, secondary skin cancers have appeared and necrosis of underlying bone has developed as very late-onset complications.
"Dermatologists are probably aware of or would expect these types of adverse events. However, what they may find surprising is that the cosmetic outcome is usually favorable after radiation treatment of tumors located at sites that would typically be considered to be very sensitive, such as the eyelids, lips and tip of the nose.
"In contrast, the trunk and extremities tend to do worse, as they are more prone to development of telangiectasias and pigmentary changes," Dr. Dawn says.
Disclosure: Dr. Dawn reports no relevant financial disclosures.