PracticeUpdate Dermatology May 2019

EDITOR’S PICKS 12

Early Melanoma Nodal Positivity and Biopsy Rates Before and After Implementation of AJCC 7 JAMA Dermatology Take-home message • This cross-sectional study included 86,846 patients diagnosed with T1 melanoma prior to the AJCC 7th edition (AJCC 7) and 54,434 patients diagnosed after AJCC 7 implementation. Results demonstrated that, after the addition of elevated mitotic rate to the AJCC 7 criteria, 3.8% fewer nodal evaluations overall were performed for T1 melanomas (P < .001), although a significantly higher proportion of patients with T1b tumors underwent nodal evaluation (48.8% vs 62.2%; P < .001), and a clinically significant change in nodal positivity rates was not observed. Most of the nodal evaluations were indicated because of a mitotic rate of 1 or more, which appeared to be associated with lymph node involvement in this study (OR, 1.93; P < .001). • Although mitotic rate was eliminated from the AJCC 8 as a differentiator between T1a and T1b melanomas, these data support continued attention to mitotic rate in patients with thin melanomas when deciding whether a sentinel lymph node biopsy should be performed.

Abstract IMPORTANCE There has been a continued increase in the incidence of newly diagnosed melanomas, most of which are T1 melanomas. The associations between changes in tumor staging, implemented with the 7th edition of the AJCC Cancer Staging Manual (AJCC 7), and sentinel lymph node biopsy rates and nodal pos- itivity rates remain to be seen. OBJECTIVE To evaluate the change that the imple- mentation of the AJCC 7 had on staging criteria

COMMENT By David G. Brodland MD T his article reviews two old AJCC melanoma staging systems, AJCC6 and AJCC7, to compare them and ostensibly sug- gest that mitosis was useful as a staging criterion. However, since January 2018, the staging system in use has been AJCC8, which notoriously dropped mitosis as a staging criterion. The defi- nitions in AJCC8 of T1a and T1b have been revised so that T1a melanomas include those <0.8 mmwithout ulceration, whereas T1b melanomas include those 0.8–1.0 mm with or without ulceration and those <0.8 mm with ulceration. The importance of assignment to T1b is that these patients, according to the NCCN guidelines, should “discuss and consider” SLNB. AJCC6, 7, and 8 all use ulceration as a criterion for T1b classifi- cation. The AJCC6 used Clark’s level IV and V as an upstaging criterion for thin melanomas (<1 mm). Clark’s level criterion was replaced by mitosis in AJCC7. In essence, the presence of a single mitosis in a “hot spot” identified on pathologic examination could qualify a person with thin melanoma for SLNB who, in absence of that single cell, would not have qualified. The obvious criticism of this systemwas that the identification of that single cell was subject to how intensely and compulsively it was searched. It is evident that significant mitotic activity is associated with more aggressive melanomas. However, the AJCC elected to drop it as a criterion, which in my opinion was a good thing. To summarize this paper, the National Cancer Data Base, which is based on hospital registries, was used comparing AJCC6 with AJCC7 patients’ rate of nodal evaluation and of nodal positiv- ity. They report a 3.8% decrease in nodal evaluation rates and a decrease in node positivity per surgery of 1%, which although, statistically significant, the authors state was clinically insignifi- cant. They conclude that continued attention to mitotic rates is warranted when deciding on the use of SLNB for thin melanoma.

In comparing Clark’s level alone, ulceration alone, and both crite- ria together for AJCC6 versus mitotic rate alone, ulceration alone, and both criteria for AJCC7 as a positively predictive criterion for nodal involvement, AJCC7 was less effective at identifying patients who would have a positive lymph node compared with AJCC6 in each comparison. Based on that, and with the understanding that increased Clark’s levels were previously deemed insufficient as a criterion for upstaging melanoma, my take-home message was that mitosis, as an upstaging criterion, was not that good and that its elimination from AJCC8 is understandable. What I did learn is that ulceration in combination with either Clark’s level IV or V or significant mitotic activity was effective at positively identifying individuals at risk for lymph node metastasis (28.3–32.8%). Perhaps one could interpret that to mean that the presence of either mitoses or greater Clark’s level verifies that the ulceration is “real” and not an incidental ulcer- ation due to abrasion, excoriation, or other nonbiological cause. What this paper doesn’t touch on is the very basic question of what SNLB is useful for. A recent paper has called into question its value in prognostication. 1 Since SLNB has been made an inte- gral part of staging, this essential but very key question is rarely discussed and the literature focuses instead on criteria to qual- ify for SLNB, overlooking whether it truly serves the purpose we hope it does. Dr. Zitelli addresses this subject below. Reference 1. Stiegel E, Xiong D, Ya J, et al. Prognostic value of sentinel lymph node biopsy according to Breslow thickness for cutaneous melanoma. J Am Acad Dermatol 2018;78(5):942-948.

Dr. Brodland is a Dermatologic Surgeon at Zitelli & Brodland PC, Skin Cancer Center in Pittsburgh, Pennsylvania.

PRACTICEUPDATE DERMATOLOGY