1. Mohs micrographic surgery was associated with significantly higher survival rates for patients with T1/T2 Merkel cell carcinoma with pathologically confirmed negative lymph nodes compared to other surgical modalities (i.e., wide local excision and narrow-margin excision).
2. Mohs micrographic surgery may be a more effective treatment for primary Merkel cell carcinoma than conventional wide-local excision.
Evidence Rating Level: 2 (Good)
Study Rundown: Merkel cell carcinoma (MCC) is a rare type of skin cancer with high mortality rates. The National Comprehensive Cancer Network guidelines state that either Mohs micrographic surgery (MMS) or wide local excision (WLE) can be used without preference. Therefore, this retrospective cohort study investigates the association between surgical excision modality (MMS, WLE, and narrow-margin excision) and patient survival for localized T1/T2 MMC confirmed by pathology. Analyses were restricted to T1/T2 tumours as they are more likely to be improved through surgery compared to later stages. Results showed that MMS was associated with significantly higher survival rates. Limitations of this study include the inability to comment on locoregional recurrence or disease-specific survival, and analyses were not controlled for patient immunosuppression. Furthermore, fewer patients were in the MMS group than the WLE group. This study also investigated hospital-based treated MCCs and did not report on treatments carried out by community-based clinics.
In-Depth [retrospective cohort]: The National Cancer Database was used to identify patients with T1/T2 MCC diagnosed between January 1, 2004, and December 31, 2018. Exclusion criteria included clinically positive lymph node disease, missing clinical lymph node status data, clinically positive distant metastatic disease, and patients not treated with surgery for T1/T2 disease. This retrospective cohort study included 2,313 patients (mean [SD] age, 71 [10.6] years; 1340 [57.9%] male). MMS had the best-unadjusted survival, with mean (SE) survival rates of 87.4% (3.4%) at three years, 84.5% (3.9%) at five years, and 81.8% (4.6%) at ten years. This was compared to survival rates of WLE: 86.1% (0.9%) at three years, 76.9% (1.2%) at five years, and 60.9% (2.0%) at ten years. The survival rates were similar between WLE and narrow-margin excision (84.8% (1.4%) at three years, 78.3% (1.7%) at five years, and 60.8% (3.6%) at ten years). Furthermore, MMS was correlated to significantly improved survival when compared to WLE (hazard ratio, 0.59; 95% CI, 0.36-0.97; P = .04). Centres with a high volume of MMC cases significantly excised by MMS vs. WLE (odds ratio, 1.99; 95% CI, 1.63-2.44; P < .001). MMS was linked to improved survival for patients with T1/T2 MMC compared to other surgical modalities (WLE and narrow-margin excision).
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