SAN ANTONIO – Patients with thin melanomas and positive deep margins on initial biopsy had the same incidence of sentinel lymph node metastasis as those with thicker melanomas, according to the results of a retrospective analysis of 260 patients with melanoma.
At least one positive sentinel lymph node was detected in 6 of 73 patients (8%) with a melanoma Breslow thickness of less than 0.8 mm and positive deep margins vs. 17 of 187 patients (9%) with a melanoma Breslow thickness of 0.8-2.0 mm, regardless of margin status (P = .82).
Immunohistochemistry was the most common method of identifying positive sentinel nodes in both the thin and thick melanoma groups (5 cases vs. 10 cases, respectively), Dr. Victor Koshenkov said at a symposium sponsored by the Society of Surgical Oncology.
The decision to perform sentinel node biopsy is largely driven by tumor thickness. When the initial biopsy of a thin melanoma shows positive deep margins, many clinicians will treat these cases as potentially thicker melanomas and perform sentinel lymph node (SLN) biopsy. There are few data on the impact of positive deep margins on surgical decision making, prognosis, and outcome, even though positive deep margins are the most common cause of incompletely measured or indeterminate tumor thickness, said Dr. Koshenkov of the department of surgery at Atlantic Health Memorial Hospital in Morristown, N.J.
He presented data from a retrospective analysis of 260 adult patients who underwent wide excision plus SLN biopsy for cutaneous melanoma from January 2004 to May 2010.
Demographics were not statistically different between the two groups, except for tumor site and Clark’s level, he said. In 53% of patients in the thicker melanoma group, the extremities were the primary tumor site vs. 38% in the thin melanoma group (P = .042), while 40% had Clark’s level IV-V vs. 22% in the thin melanoma group (P less than .001).
Multivariate regression analysis revealed that only female gender (P = .046; odds ratio, 2.68) and Clark’s level IV-V (P = .024; OR, 3.54) were significantly associated with an increased risk of positive SLNs. Belonging to the thin melanoma group versus the thicker melanoma group was not significant (P = .66; OR, 1.29) Dr. Koshenkov said.
The presence of residual disease approached, but did not reach, statistical significance (P = .062; OR, 2.60). Residual disease was found in about 20% of both groups. Only 4 of the 73 patients (5.5%) with positive SLNs in the thin melanoma group required further reexcision with wide margins.
Only 1 of the 23 sentinel node–positive patients went on to have additional positive nodes on completion of lymph node dissection, he said.
"Patients with thin melanomas and positive deep margins on initial biopsy have an incidence of SLN metastasis statistically no different than patients with thicker melanomas," Dr. Koshenkov concluded. "Thus, we believe that thin melanomas with positive deep margins should be treated with wide excision and a sentinel lymph node biopsy. Of course, these findings should be tested and verified in larger, multi-institutional databases."
During a discussion of the study, the audience questioned the ability to make almost a practice-changing conclusion based on the small number of patients and the low incidence of positive SLNs in the thicker melanoma group. Dr. Koshenkov replied that the reason the rate of sentinel node positivity was lower than predicted in this group was that a larger proportion of patients had melanomas 0.8-1 mm in depth, rather than 1-2 mm in depth.
Another attendee remarked that before concluding that every patient with a positive deep margin on initial biopsy needs to undergo SLN biopsy, it is important to know how many patients with positive sentinel nodes had a positive deep margin as their only indication or whether factors such as mitotic rate or ulceration played a role. Dr. Koshenkov said mitotic rate was not analyzed because it was not regularly included in the pathology report at the time of the review, and that ulceration and Clark’s level IV were factored into the multivariate analysis.
The authors said they had no relevant financial disclosures.