Outcomes of Patients Undergoing Sentinel Lymph Node Biopsy for Merkel Cell Carcinoma

Merkelcell.org Summary

Merkel cell carcinoma (MCC) is a rare but aggressive skin cancer that often spreads to nearby lymph nodes. A sentinel lymph node biopsy (SLNB) is a standard test that checks the first lymph nodes that cancer cells are most likely to spread to. This helps doctors see if the MCC has started to spread and figure out what stage the MCC is. This study looked at whether having a positive versus negative SLNB changed a patient’s risk of MCC returning.
The researchers looked at 342 MCC patients in the United States between 1996-2022 who were treated with surgery and SLNB. Overall, 41% of patients had cancer cells in their lymph nodes (a positive SLNB), showing a common pattern of MCC spread. They further found that patients with larger tumors (bigger than 2 cm) and weaker immune systems (immunosuppressed) were more likely to have a positive SLNB. However, more than 1 in 10 patients with small tumors who were at lower risk of the MCC spreading, still had a positive SLNB. The risk of MCC returning within 5 years after diagnosis was higher for patients with a positive SLNB (40%) than those with a negative SLNB (12%). 86% of patients who had a positive SLNB received more treatment to that area, most often radiation therapy.
These results indicate that SLNB is a powerful tool to understand a patient’s risk of MCC returning, which helps guide decisions about treatment, such as who should receive radiation therapy to their lymph nodes.

Abstract

Background

Merkel cell carcinoma (MCC) is a rare, cutaneous malignancy with a propensity for nodal metastasis, for which prognostic factors remain poorly characterized.

Patients and Methods

All patients treated from April 1996 through December 2022 by wide excision and sentinel lymph node (SLN) biopsy for clinically localized MCC at a single institution were included. Logistic regression was used to evaluate factors associated with a positive SLN, recurrence, and disease-specific death (DSD). Cumulative incidence functions estimated recurrence and DSD with death from other causes as a competing risk.

Results

Of 342 patients with MCC, 140 (41%) had a positive SLN. In multivariable analysis, tumor size > 2 cm, lymphovascular invasion (LVI), and more recent diagnosis were significantly associated with a positive SLN. Among the lowest-risk patients (≤ 1 cm tumors and without LVI), 17% had a positive SLN. Most patients (86%) with a positive SLN received further nodal treatment. At 3 years, only 3% of these patients experienced a recurrence within the same nodal basin. A positive SLN was the only factor independently associated with recurrence (39% vs. 12% at 5 years, p < 0.001). The 5-year incidence of DSD was 3.5%, 10%, and 15% (p = 0.002) for patients with stage I, II, and IIIA disease, respectively.

Conclusions

SLN biopsy for patients with MCC is frequently positive, which is associated with increased risk of recurrence and DSD. Even in the absence of identifiable risk factors for SLN metastasis, the SLN positivity rate is > 10%. SLNB appears to inform prognosis in MCC and guides exceptional regional control.