Adding mitotic rate increases positive sentinel node detection

December 1, 2017

Abstract

Introduction

Prior to 2009, thin melanomas (< 1.01 mm) were sub-divided into T1a or T1b based on presence/absence of ulceration.  The 2009 American Joint Committee on Cancer (AJCC) 7th staging guidelines expanded the T1b staging for melanoma to include patients with mitotic rates with mitotic rates £1, whether or not ulceration was present. The National Comprehensive Cancer Network (NCCN) guidelines recommend consideration of sentinel lymph node biopsy (SLNB) in patients with T1b melanomas.  We sought to determine how the addition of mitotic rate affected the detection of positive nodes.

Methods

The National Cancer Database was retrospectively queried for patients with thin melanoma (Breslow depth < 1.01 mm) from 2004 to 2013. Demographics, clinical characteristics, surgical treatment, and final pathologic stage were evaluated.

Results

For analysis, 149,273 patients were included. Thirty-five percent of all patients underwent an SLNB and 9.8% were positive.  After 2010, there were 20,145 patients who had either ulceration and/or mitotic rate £1.  Of these, 61.1% underwent SLNB and 12.3% of these were positive. Of patients who underwent SLNB had a mitotic rate  £1, 3.7% had ulceration and 11.0% of their nodes were positive.  A total of 80.6% of patients undergoing SLNB had a mitotic rate £1, and 8.8% of these nodes were positive. Patients with both ulceration and a mitotic rate £1 comprised 15.7% of patients undergoing SLNB, and 30.8% of these nodes were positive.

Conclusions

The addition of mitotic rate to T1b staging for melanoma found an additional 868 positive sentinel lymph nodes in patients who would have not been recommended for SLNB under the AJCC 6th edition.

Source:

Isom, C, et al.  Addition of Mitotic Rate to the 7th Edition American Joint Committee on Cancer Melanoma Staging Increases the Detection of Positive Sentinel Nodes: A National Cancer Database Study.  Journal of the American College of Surgeons 2017;225(4), Supplement 1:Page S198
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