Factors associated with Mohs micrographic surgery in dermatofibrosarcoma protuberans of the head and neck: A cohort study

Dear Editor,

Dermatofibrosarcoma protruberans (DFSP) of the head and neck is a rare, locally infiltrative, low-grade sarcoma with the incidence in African-American patients being almost twice the rate among Caucasian patients. Prior studies have shown that tumours treated with Mohs micrographic surgery (MMS), when compared with other surgical modalities, have a significantly lower recurrence rate and better aesthetic outcomes in cosmetically sensitive areas, such as the head and neck.¹ However, given the high costs and prior authorization often associated with MMS, it remains unclear which patients are typically eligible to receive MMS for DFSP despite its suggested therapeutic success.

We aimed to study predictors of MMS to determine which factors led to this chosen treatment modality. We queried the National Cancer Database (NCDB) from 2004 to 2016 for all cases of DFSP lesions of the head and neck. The NCDB is the largest cancer database within the United States and gathers information from more than 1500 accredited cancer facilities in the United States and Puerto Rico, collecting roughly 70% of all cancer diagnoses in the United States annually.² We restricted our study to histologically confirmed cases of DFSP using ICD-O-3 histology codes. Only cases with lesions of the head and neck, including the lip, eyelid, external ear, scalp, neck and other unspecified parts of the face were included. After completion of the database review, univariable and multivariable analyses were performed using Microsoft Excel (Microsoft, Seattle, WA) and SAS Software (SAS Studio Release 3.8, Cary, North Carolina). Clinical and demographic characteristics were compared among patients receiving each type of surgery using t-tests, chi-squared and Fisher’s exact tests. Multivariable logistic regression was then performed to assess predictors of receipt of MMS based on analysed variables with less than 50% missing data.

A total of 778 patients underwent surgical procedures. Of the included patients, 434 (56.0%) of the patients were male and 344 (44.2%) of the patients were female. The average age of the included patients was 42.2 ± 15.7 years. Patients were divided into surgical treatment groups and 101 (12.9%) were treated with MMS, 371 (47.7%) with wide local excision (WLE) and 306 (39.3%) with other surgeries.

When comparing MMS independently to all other treatments [Table 1], the incidence of MMS in academic centres remained significantly greater than in community or integrated network programmes (p = 0.0049). Furthermore, for individuals with higher incomes (≥$63,000), there was a higher incidence of MMS (p = 0.0176, Table 1). On multivariable logistic regression analysis [Table 2] assessing predictors of MMS including all variables in Table 1, higher incomes independently predicted treatment with MMS compared to those with lower incomes (≤$38,000) when controlling for confounders (Odds ratio: 2.8, 95% confidence interval: 1.3, 6.1, p = 0.0047).

On chi-square analysis comparing Caucasians to all other racial groups (African-Americans and others), 86 of 603 (14.3%) Caucasians and 15 of 175 (8.6%) patients of other races received MMS (p = 0.0486).

Our analysis shows that MMS was performed more often at an academic centre. The treatment of cutaneous malignancies of the head and neck often requires multidisciplinary care, especially for rarer tumours like DFSP which is more feasible at academic centres due to an increased number of resources and expertise available. Furthermore, higher annual incomes were also independently predictive of MMS. This sheds light on healthcare disparities which occur with regard to accessing MMS. Surveys have shown that providers have asked for advanced deposits and given financial disclosures prior to MMS, possibly disadvantaging low-income patients. MMS has been perceived to be an expensive modality of treatment; however, previous studies have demonstrated its cost-effectiveness, especially when compared to other surgical procedures.¹ For example, in typical surgical excision, 32–39% of cases require a follow-up procedure following initial surgical resection to ensure clear margins.³ These follow-up surgeries also lead to a greater volume of tissue removed and significant cosmetic consequence.^1,4 In addition, our study showed a lower percentage of African-American patients with DFSP of the head and neck (8.7%) treated with MMS compared to Caucasian patients (14.3%), similar to previous studies showing greater MMS utilization in Caucasian patients as compared to non-Caucasian patients,¹ exacerbating higher incidence of DFSP and worse survival in African-American patients.⁵ To fully explore impact of racism on surgery received, future studies should be performed in single-ethnic nations. Limitations include the self-reported nature of NCDB and lack of specific information as to which centres MMS was available.

In summary, ensuring equitable access to MMS for treatment of DFSP is essential to disease outcome and patient quality of life. We underscore income status as a significant independent predictor of MMS receipt when controlling for insurance status, race, age, sex and other confounders.