Study: MMS may be most effective tx for rare aggressive malignancies

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Danville, Pa. - The benefits of Mohs micrographic surgery (MMS) in preserving tissue and improving cure rates of common cutaneous malignancies are well-established, and new research concludes that the procedure is also the most effective therapy for rare aggressive cutaneous malignancies.

Such malignancies make up only a small percentage of overall cutaneous malignancies, and because of their infrequent presentation, the effectiveness of MMS on the tumors is poorly defined, according to researchers with the Geisinger Medical Center here.

The few reports that have examined MMS for such tumors focused either on a single type of malignancy or were conducted at multiple clinic sites, the researchers say.

"Nevertheless, our hypothesis was that Mohs would be more effective than traditional therapies," he adds.

Retrospective review

To get a more comprehensive view of MMS value and efficacy in the rare malignancies, researchers conducted a retrospective chart review of 26,000 cases treated with MMS at the Geisinger Medical Center's department of dermatology over the course of a 16-year period (Dermatol Surg. 2007 Mar;33(3):333-339).

The types of diagnoses considered in the review included poorly differentiated squamous cell carcinoma (PDSCC); dermatofibrosarcoma protuberans (DFSP); microcystic adnexal carcinoma (MAC); extramammary Paget's disease (EMPD); Merkel cell carcinoma; and sebaceous carcinoma. For the latter two, the cases were too few to offer a meaningful analysis of recurrence rates.

In all other cases for which follow-up rates were available, the findings showed recurrence rates with Mohs that were dramatically lower than could have been expected with standard surgeries.

For poorly differentiated squamous cell carcinoma, 85 cases were available for follow-up, with a local recurrence rate of 6 percent at a mean follow-up time of 45 months. While there are few comparative studies in the literature, a previous review of PDSCC treated with MMS had a relatively low cure rate of only 67.4 percent; however, that was compared with an even lower cure rate of only 46.4 percent for tumors treated with non-Mohs modalities (J Am Acad Dermatol. 1992;26:976-990).

For dermatofibrosarcoma protuberans, which most commonly affects patients between the ages of 40 and 50, among the 35 cases there were no local recurrences after MMS at a mean follow-up of 39 months, whereas marginal recurrence rates reported with traditional surgery have been as high as 20 percent to 50 percent.

For microcystic adnexal carcinoma, a slowly growing, locally aggressive tumor originating in the eccrine gland, there were 25 cases with a local recurrence rate of 12 percent at a mean follow-up of 39 months. This represented the highest recurrence rate of tumors reviewed. Still, recurrence rates remained favorable when compared with other surgical modalities, which have been reported to be up to 60 percent.

For extramammary Paget's disease, there were 10 cases with no local recurrences at a mean follow-up of 34 months. Recurrence rates experienced by Mohs patients with this type of carcinoma in the literature were higher, ranging from 8 percent to 27 percent, but they still compare favorably with the non-MMS approach of wide local excision with conventional surgery, which has a reported marginal recurrence of 30 percent to 60 percent, the researchers report.

Mohs most effective

"Collectively, our data on PDSCC, DFSP, MAC and EMPD, combined with other studies in the literature, show that MMS is the most effective therapy for these rare, aggressive cutaneous malignancies," the researchers write.

Despite the findings, Mohs surgery may often not be the first choice of treatment for all aggressive melanomas, Dr. Thomas tells Dermatology Times.

"For one thing, Mohs is dependent upon a certain subset of tumor type that is contiguous and doesn't have a high risk of metastasizing prior to the surgery, so some types of aggressive tumors are, in fact, probably not best treated with Mohs," he says.

"But I also suspect that aggressive tumors in general are still being treated the majority of the time with traditional surgical techniques because of a lack of awareness that Mohs is a good option for these types of cancers."