Treating patients with multiple SCCs requires clearing dermal disease first, then addressing field in situ disease topically; physicians are frequently required to make judgment calls, an expert says.
New York - In the absence of large-scale comparative studies clearly favoring one approach over another, treating multiple squamous cell carcinomas (SCCs) or high-risk single SCCs often requires dermatologists to make clinical judgments, an expert says.
"When a patient walks into the office and their skin is covered with the spectrum of actinic keratosis (AK), SCCIS and invasive SCC, it's a bit difficult to know where to begin. That was certainly true for me when I first started to see these patients," says Chrysalyne D. Schmults, M.D., director of the Mohs Micrographic Surgery Center, Dana Farber/Brigham & Women's Cancer Center, Boston.
However, she says, "The key is to focus first on lesions which you believe have a dermal component. These invasive SCCs must be surgically removed."
"One should obtain histologic confirmation that the margin is clear when dealing with invasive SCC," she says.
Some dermatologists perform desiccation and curettage (D&C) on invasive SCCs, because it's faster than surgery, Dr. Schmults says.
"But the problem with D&C is that there's no assurance that you've really gotten out all of that dermal disease. And these patients with multiple lesions are prone to recurrences, often with aggressive, high-risk cancers," Dr. Schmults tells Dermatology Times.
For SCC on the head, Dr. Schmults prefers Mohs surgery, due to its accuracy and tissue sparing.
After clearing invasive disease, for patients who have large areas of AK/SCCIS, she says, "I try not to biopsy lesions that look like they're just in situ. I will first try to treat such lesions with a topical preparation, preferably 5 fluorouracil (5FU)."
Dr. Schmults says she prefers this agent to imiquimod for treating large surface areas, because the latter isn't designed for large areas, and patients frequently experience significant side effects due to systemic absorption when it's used on large surface areas.
Rather than tackling each epidermal lesion individually, she says, "Field disease needs a field treatment. Liquid nitrogen is not effective for people who have this kind of field cancerization, where large surfaces on their skin have SCC in situ or actinic keratoses."
Once a patient has completed 5FU therapy, Dr. Schmults says, "The patient needs to be watched closely. Any lesion that didn't respond to the 5FU needs to be biopsied. Failure of topical therapy indicates that there may be a dermal component, or for whatever reason, this is a more aggressive lesion that's not going to respond to topical therapy."
Patients with multiple SCCs are more likely to form individual high-risk tumors that pose a risk of metastasis, and even death.
Traditional definitions of high-risk SCC tumors depend on the tumor's diameter, depth, recurrence, perineural spread, location (lip, anogenital, ear) and histology, as well as whether the patient is immunocompromised, Dr. Schmults says.
However, she says that SCC prognostic data are scarce, lagging far behind the modeling that's available in melanoma.
Accordingly, she says, "There's a lot of controversy about how to treat high-risk SCCs."
Nevertheless, Dr. Schmults says, "I get CT scans on patients with tumors 2 cm or larger in diameter (1.5 cm on the lip), that penetrate beyond subcutaneous fat, that have significant perineural invasion, or are multiplying or rapidly recurrent to rule out subclinical lymph node disease. There's little downside to doing it in these high-risk cases, other than the cost."
Regarding adjuvant RT, Dr. Schmults says, "Our review shows that there haven't been adequate studies to compare adjuvant RT versus surgery alone. In fact, only one small, nonrandomized study has compared outcomes of the two treatments," she says.
Accordingly, Dr. Schmults says, "I reserve adjuvant RT for cases of perineural invasion of nerves 0.1 mm in diameter or larger, or nerves large enough to have a name."
She also uses adjuvant RT in cases where she's uncertain about surgical margins, perhaps because the tumor was highly infiltrative or there was significant tumor involvement close to the deep margin, she says.
"Although we have no studies to show an advantage in cutaneous SCC, benefit has been shown in head and neck mucosal SCC," she says.
Additionally, Dr. Schmults says that if she's treating a tumor she believes is very high-risk - such as those with a diameter of 3 cm or more, involvement of structures below the fat, or infiltrative histology making margins more uncertain - she frequently takes an extra Mohs layer after achieving a clear surgical margin to ensure that she gets an adequate deep margin.
"What one really must worry about with these kinds of aggressive tumors is not so much recurrence in the dermis, which will be visible relatively quickly, but deep recurrence‚ in the periosteum or bone, for example."
Disclosure: Dr. Schmults reports no relevant financial interests.
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