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This new data indicates that this not widely-practiced surgery for MCC, while effective, may first require initial implementation at higher-volume, regional centers for MCC due to existing infrastructure.
In cases of initial Merkel cell carcinoma (MCC) where regional lymph node disease is pathologically determined to be negative, new findings suggest Mohs micrographic surgery instead of wide local excision could lead to greater rates of patient survival.1
The study which led to these findings assessed the link between a surgical approach with overall rates of survival following the excision of localized T1/T2 MCC, given the apparent need for more accurate research on the impacts of different surgical options on patient outcomes.2
Given that compared with other types of cutaneous cancers such as malignant melanoma, the highest rates of associated mortality are seen with MCC, this research was seen as invaluable. It was authored by John A. Carucci, MD, PhD, from The Ronald O. Perelman Department of Dermatology at New York University’s Grossman School of Medicine.3
“In the current analysis, we aim to evaluate the association of the surgical excision modality and patient survival for pathologically confirmed localized T1/T2 MCC,” Carucci and colleagues wrote. “We limited our analysis to T1/T2 tumors because they were determined to be more likely amenable to any surgical approach.”
The investigators conducted a retrospective cohort study in which they utilized the National Cancer Database (NCDB) to assess adults who have been diagnosed with T1/T2 MCC in the time between January of 2004 and December of 2018. The study participants showed confirmed negative regional lymph nodes and were consequently treated through surgery.
The NCDB database, known to be a wide-ranging clinical surveillance dataset which covers over 70% of malignant neoplasms that are newly-diagnosed in the US, was used as the investigators’ primary source. Prior cutaneous oncologic studies which have been conducted have also used NCDB data.
The study population was made up of adults who had MCC, and they were identified via the International Classification of Diseases for Oncology, 3rd Edition histology code 8247 and the primary site codes C44.0 - C44.9 in the time between January of 2004 and December of 2018.
The study’s cohort was further refined by the team excluding those with missing clinical lymph node status, clinically positive lymph node disease, clinically-negative distant metastatic disease,non-T1/T2 disease, no surgical excision, missing radiotherapy data, and pathologically negative lymph node(s) which were unconfirmed. Potential study participants which had other active malignant neoplasms, as well as those diagnosed in the year 2019, were also excluded from the research.
The investigators used a statistical analysis which involved staging, evaluations of pathologic lymph nodes, surgical approaches, stratification of facility volume, primary site definitions, radiotherapy receipt, and baseline risk factors among those in the high-risk group.
The research team’s main focus was on overall survival, and several different analyses such as Kaplan-Meier and multivariable regression, were done by the team to examine the factors linked to surgical approach as well as treatment outcomes.
The investigators ended up assessing the data of 2313 individuals, all of whom had an average age of 71 years and 57.9% of which were male. The study outcomes of varying treatment approaches were assessed by the team.
The research team reported that Mohs micrographic surgery for excision ended up having the most favorable rates of survival, without adjusting for other factors. They added that over 3, 5, and 10 years, it was shown that the unadjusted survival rates for Mohs micrographic surgery were found to be 87.4%, 84.5%, and 81.8%, respectively.
In contrast, those individuals given wide local excision showed rates of survival of 86.1% at 3 years, 76.9% at 5, and 60.9% at 10. The investigators also noted that narrow-margin excision showed similar survival outcomes to wide local excision.
They found that survival rates for narrow-margin excision were shown to be 84.8%, 78.3%, and 60.8%, respectively. After conducting their multivariable survival analysis, the research team found that Mohs micrographic surgery was associated with much better rates of survival versus wide local excision.
The investigators added that the hazard ratio for Mohs compared to wide local excision was shown to be 0.59 (with a 95% confidence interval of 0.36 - 0.97, and a P-value of 0.04), demonstrating higher survival with Mohs.
Additionally, the team found that high-volume centers which specialized in treating Merkel cell carcinoma were shown to be more likely to use Mohs over wide local excision when compared to other types of centers.
“These data suggest that MMS may provide a survival benefit in the treatment of localized MCC, although further prospective work studying this issue is required,” they wrote. “Future directions may also focus on elucidating the benefit of adjuvant radiotherapy in localized cases treated with MMS.”