ORLANDO – Although Mohs surgery remains a mainstay of skin cancer treatment, some patients benefit from targeted brachytherapy of their basal or squamous cell carcinoma lesions, according to Dr. Michael E. Kasper.
Patients who are elderly, infirm, or on blood thinners are good candidates for noninvasive brachytherapy using high-dose, small surface applicators, Dr. Kasper said. This therapeutic strategy also works well for treating lesions in anatomic locations at risk for delayed surgical healing.
"We are treating various small lesions with these surface applicators," Dr. Kasper said. For example, superficial squamous cell carcinoma (SCC) lesions up to 2 cm can be targeted "where we feel comfortable about the visible margins," he said at the annual meeting of the Florida Society of Dermatology and Dermatologic Surgery.
"We also see patients who are tired of [invasive resection] or who are poor candidates for surgery, and that is really the bulk of our patients," Dr. Kasper said. He assured meeting attendees that his goal as a radiation oncologist is not to take skin cancer patients away from dermatologists. "We’re not interested in treating 40- or 50-year-olds and really competing," said Dr. Kasper of Lynn Cancer Institute at Boca Raton (Fla.) Regional Hospital. "We are interested in working with dermatologists and really helping you with those patients who might be neglected or who are at high risk of developing a serious recurrence."
Neglected patients may include nursing home residents who do not get medical attention for their skin cancer in its earlier stages, he said.
Available data point to good local control and cosmesis for a majority of patients, Dr. Kasper said. A typical patient might experience acute effects such as crusting and some mild erythema about 10 days to 2 weeks after brachytherapy of a well differentiated SCC lesion of the lower extremity. More brisk erythema also occurs in about 10%-15% of patients, Dr. Kasper said.
Late hypopigmentation also develops in about 10% of patients, he said. "We are also seeing a few telangiectasias, but it’s fairly mild."
Interpret postradiation therapy biopsies with caution, Dr. Kasper warned. Of the 240 patients treated to date at his institution over about 6.5 years, there were three documented recurrences, including a couple at 3 and 4 months. "While we are counting those as recurrences, they probably aren’t. That’s way too early to biopsy these lesions." Use discretion and ideally wait until you see clear progression prior to performing a postradiation biopsy, he said. "There certainly are false positives that occur due to delayed tumor regression. The cancer cells die when they reproduce and many of these are slow growing tumors. So we would not expect them to all be completely resolved at 3 or 4 months although clinically, on the surface, they can appear that way."
Historically brachytherapy was delivered as a low-dose treatment over a long period of time at many sessions. Low-dose brachytherapy is typically in the 0.4 to 2.0 Gy/hr range, medium dose is greater than 2 and up to 12 Gy/hr, and the high dose exceeds 12 Gy/hr.
Availability of high-dose rate brachytherapy was a "major breakthrough" because patients no longer had to lie in the hospital all weekend to receive treatment. "It was a bit controversial at first, but now there are really good data to show there are radiobiologic reasons why the high dose rate may actually be advantageous in killing cancer cells compared to this low trickle effect that we were using with low-dose regimens."
Dr. Kasper determined that up to 30 sessions of low-dose rate brachytherapy can be a real impediment to patient compliance and worked to design a safe and effective regimen delivered in fewer sessions. "We wanted to be at six treatments and worked backwards." Striking a balance between the dose-response rate and the potential late side effects was another consideration.
A meeting attendee asked about the relative cost of brachytherapy, compared with other treatment modalities. Brachytherapy is generally more expensive than Mohs surgery, Dr. Kasper replied. The avoidance of cancer recurrences will hopefully justify the higher initial costs, he said. He added that brachytherapy costs are coming down, more so in outpatient centers, compared with hospital settings.
Dr. Kasper said he receives consulting fees from Nucletron/Elekta.