AUSTIN, TEX. — The commonly accepted standard of using 5-mm margins for surgical excision of melanoma in situ may not be enough to clear the large majority of tumors, said Dr. Joy Kunishige.
Speaking at the annual meeting of the American College of Mohs Surgery, Dr. Kunishige, a dermatologist in private practice in Pittsburgh, said that since several studies have shown a 5-mm margin to be inadequate, she and her colleagues gathered the latest evidence on clearance rates to update previous National Institutes of Health guidelines, set in 1992 (NIH Consens. Statement 1992;10:1–26). The goal was to clear at least 97% of tumors.
They evaluated all primary melanoma in situ cases that were collected as part of a prospective database started in 1982 at the practice. The database included 1,072 patients with 1,120 primary tumors. Of the patients, 675 (63%) were male, mean age was 65 years, and mean follow-up was 4.7 years. A total of 593 (53%) of the lesions were on the face, 235 (21%) were on the extremities, and 201 (18%) were on the trunk, with the remainder in other locations.
All lesions were excised using the fresh tissue technique of Mohs, with frozen section examination of the margin.
Using 6-mm margins, 86% of the tumors were cleared. With a 9-mm margin, there was a 98% clearance rate; and with a 12-mm margin, a 99.4% clearance rate, said Dr. Kunishige.
The 9-mm margin was equally effective regardless of sex, location, or diameter of the lesion, she said. The overall 5-year survival was 93%; the 5-year melanoma in situ survival was 99.5%. Three patients died of melanoma in situ. Two died from a separate invasive melanoma, and 90 died of other causes, free of melanoma. The overall survival curve was what would have been expected for this age group, she said.
The overall recurrence rate in this evaluation was 0.3%. Three patients had a local recurrence, with reappearance of tumors at 9, 10, or 11 years.
Dr. Kunishige and her colleagues concluded that a 9-mm margin was superior to the 6-mm margin, with a P value of less than .0001.
She reported no disclosures.
A 5-mm margin may not be adequate for removing the majority of tumors. In this study, clearance was 98% with a 9-mm margin and 86% with a 6-mm margin. COURTESY JOY KUNISHIGE, M.D.