SAN DIEGO – Aggressive skin cancers can recur, spread, and kill – and these lesions deserve special consideration after even an apparently successful Mohs procedure.
"Mohs is especially well suited to identify the rare patient who has a high-risk profile for local recurrence or metastasis," Dr. David Hodgens said at a meeting sponsored by the American Society for Mohs Surgery. "We can work together to develop radiotherapy techniques that treat both the primary site and the nodal basins to minimize toxicity and give the patient a better chance of a cure."
The Mohs surgeon is unlikely to see many patients who will need postoperative radiotherapy, said Dr. Hodgens, director of radiation oncology at Scripps Memorial Hospital, La Jolla, Calif. "Keep in mind the vast majority of patients will not need this – but be on the lookout for those who might."
Any skin cancer – squamous or basal cell carcinoma, Merkel cell tumor, melanoma or angiosarcoma – can be increasingly dangerous if certain risk factors are present, Dr. Hodgens said. Risk factors for local recurrence or metastatic spread include a lesion size greater than 2 cm; depth greater then 4 mm or a Clark level IV-V; location on the ear or lip, or within a scar; or perineural or periosteal invasion. Immunosuppressed patients are at particularly high risk, as are those with an already recurrent lesion. "A lesion that has recurred after prior treatment is one of the greatest risks of further recurrence or metastatic spread," he stressed.
Electron beam radiation is the best treatment for high-risk skin cancers. "Electrons are essential in treating the postoperative Mohs patient. If your radiation oncologist is not using electrons, find one who is," he said.
High-energy x-rays are also used, but mostly to cover a nodal basin where spread is suspected. But electrons have a unique property that allows a narrow beam to deliver 90% of its energy to a prespecified depth and then very rapidly decrease that energy as the beam goes deeper into the tissue. "Electrons provide penetration to a desired depth without the through transmission of x-rays," Dr. Hodgens said.
Post-Mohs radiation calls for a large treatment field that encompasses the entire surgical field and generous margins. "We try to get at least 2 cm around the surgical bed," he said. Patients typically receive daily treatments for 5-7 weeks, with 1.8-2 Gy/day to the primary site. The total radiation dose is usually around 50-60 Gy.
"We treat them as seriously as we do any of our patients with breast, lung, or brain tumors," Dr. Hodgens said. "They have the potential to die of their skin cancer. This is a long aggressive course of treatment designed to give the best chance of cure."
X-rays can be added to treat the associated nodal basin, if nodal spread is a concern. "The toxicity of adding nodal radiation is minimal," Dr. Hodgens said. "It’s very well tolerated, with mostly just mild erythema. It’s really an easy thing to do and very worthwhile."
There are few studies published on postoperative radiation for strict indications after well-performed Mohs surgery. Most recently, a Greek study of 315 patients found that post-Mohs radiation was associated with a 92% reduced risk of recurrence (Eur. J. Cancer 2010;46:1563-72).
Last year, an Australian study of 118 patients with cutaneous head or neck cancers found that surgery plus radiotherapy improved survival rates, even among those with perineural involvement – a very poor prognostic factor. The 5-year local control rates were 90% for those with histologically proven perineural involvement and 57% for those with symptoms of perineural involvement (Head Neck 2009;31:604-10)
Dr. Hodgens had no financial disclosures.