Larger Surgical Margins Tied To Better Outcomes In Merkel Cell Carcinoma

In patients with localized Merkel cell carcinoma, larger local excision (LE) margins are associated with longer overall survival, as is the use of radiotherapy, according to a large new study.

"The study demonstrates the importance of achieving greater than 1 cm surgical margins and the importance of post-operative radiation therapy for patients with stage I-II Merkel cell carcinoma," Dr. Brian C. Baumann of Washington University School of Medicine in St. Louis, Missouri, told Reuters Health by email.

Patients with Merkel cell carcinoma have a high risk of locoregional recurrence and metastatic disease, with an estimated five-year disease-specific mortality between 15% and 33%, Dr. Baumann and colleagues note in JAMA Dermatology. But data on optimal margin size and use of adjuvant radiotherapy are sparse.

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Using records from the National Cancer Database, the researchers identified more than 6,000 patients with stage I-II Merkel cell carcinoma who underwent local excision between 2004 and 2015.

With a median follow-up of 35 months, the team found that regardless of tumor subsite, patients who had had surgery with local excision margins larger than 1 cm had significant greater overall survival than those with smaller excision margins (hazard ratio, 0.88; P<0.001).

Five years after surgery, margins of 1.0 cm or less were associated with a net survival of 76.7%, significantly less than the 89.8% survival seen in those with larger margins.

The advantage of larger margins also extended to patients with less aggressive disease, including factors such as being immunocompetent and having no lymphovascular invasion (HR, 0.87).

On multivariable analysis, adjuvant radiotherapy was associated with significant improvements in overall survival in all LE-margin subgroups, with hazard ratios ranging from 0.66 to 0.77.

Dr. Christopher K. Bichakjian, professor and chair of the department of dermatology at the University of Michigan, in Ann Arbor, told Reuters Health that the study "is an important contribution to the ongoing discussion about the surgical margins for local excision of Merkel cell carcinoma."

"While the retrospective nature and absence of important treatment-specific and outcome variables in National Cancer Database datasets limits interpretation, the findings support the general concept that wider treatment margins, whether with surgery or adjuvant radiation therapy, are associated with more favorable outcomes in Merkel cell carcinoma," said Dr. Bichakjian, who was not involved in the research. "Equally important is the finding that excessively wide margins, greater than 2 cm, did not provide additional benefit."

—David Douglas

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