Questions raised about outcomes with Mohs surgery for melanoma

Skin cancers

By Mardi Chapman

14 Apr 2021

Patients with T1a-T2a invasive melanoma treated with Mohs micrographic surgery (MMS) at academic and higher case volume facilities have better overall survival than patients treated at nonacademic and low-volume facilities.

A US study of over 4,000 patients treated at 462 centres reported 417 deaths during the ten-year study period.

Survival at academic centres was 95.3% at 3 years, 90.2% at 5 years, and 77.4% at 10 years compared to 95.0% at 3 years, 90.7% at 5 years, and 80.5% at 10 years after treatment at nonacademic centres

Using multivariate analysis, it found treatment at academic facilities versus nonacademic facilities was associated with a nearly 30% reduction in the hazard of death (hazard ratio [HR] 0.730; 95% CI, 0.596-0.895).

“Similarly, treatment at top decile-volume was associated with improved survival compared with low volume facilities (HR 0.795; 95% CI, 0.648-0.977).”

The study, published in JAMA Dermatology, said facility characteristics were significantly associated with long-term survival after Mohs for early-stage invasive melanoma.

“Although the absolute differences in survival between centres that we found for early-stage invasive melanoma are more modest than those found for more aggressive cancers, this magnitude of difference should be considered in the context of the higher incidence of early-stage melanoma as well as its favourable prognosis.”

They suggested academic facilities and high volume centres might be more likely to provide care consistent with clinical guidelines, involving multidisciplinary management, more extensive staging or different immunochemical stains.

“Although MMS is not yet included in national guidelines for invasive melanoma, it is possible that high-volume academic centres are more likely to follow the most current evidence and recommendations for the procedure in lieu of such guidelines,” they said.

They also noted the case volume-outcome relationship may be especially prominent in the case of Mohs for melanoma, where there is relatively less experience with the procedure than with standard surgical excision, as well as a lack of consensus on best practices.

“Further study of the underlying reasons for these differences in survival, as well as the development of consensus standards for the technique, may help to reduce such variations in patient outcomes across treatment centres,” they concluded.

An accompanying editorial in the journal said the results must be interpreted with some caution for a variety of reasons.

For example: “… it is challenging to demonstrate a true survival benefit based on retrospective data among a cohort of patients with established 5-year disease-specific survival rates exceeding 95%.”

The editorial also noted the hospital-based findings might not apply to “community private practice surgeons performing MMS with extensive experience…”.

Nevertheless the study raised important questions about standardised use of Mohs and minimum case-volume required for competency.

Australian perspective

Dr David Francis, an ACD accredited Mohs specialist, told the limbic that neither he or his colleagues at Brisbane’s Dermatology Specialist Centre use Mohs for melanoma despite being the only accredited training centre for Mohs in Queensland.

“There are certainly other people in Australia who are doing melanoma with Mohs surgery but I don’t … I’m a bit uncomfortable with it and would rather wait.”

“It isn’t that people shouldn’t be doing it, it’s just we’ve decided that we will wait and let the pathologist do the melanomas.”

He said the choice of immunochemical stains and frozen versus paraffin sections were part of the considerations in order to read melanoma more clearly.

ACD president Dr Francis said Mohs quality in Australia was maintained through College accredited training, an annual quality assurance program and minimum caseload.

“In our practice where there are 10 dermatologists, not all working full time, we have had weeks when we have had more than 20 Mohs in a week.

“And even on an average week it would be unusual for us not to have 5 and not uncommon for us to have five each.”

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