Treatment of dermatofibrosarcoma protuberans with Mohs micrographic surgery is associated with lower odds of postoperative radiotherapy compared to wide local excision

To the Editor: Dermatofibrosarcoma protuberans (DFSP) is a locally aggressive cutaneous sarcoma that is principally treated with Mohs micrographic surgery (MMS) or wide local excision (WLE). For recurrent or persistent disease that becomes unresectable, radiotherapy (RT) or chemotherapy is recommended.1NCCN clinical practice guidelines in oncology. Dermatofibrosarcoma protuberans version 1.2022. National Comprehensive Cancer Network (NCCN Guidelines).https://www.nccn.org/professionals/physician_gls/pdf/dfsp.pdfDate accessed: December 29, 2021Google Scholar However, there is significant morbidity, including pain, fibrosis, lymphedema, and secondary malignancies, associated with RT.2Ashack K.A. Kuritza V. Visconti M.J. Ashack L. Dermatologic sequelae associated with radiation therapy.Am J Clin Dermatol. 2020; 21: 541-555https://doi.org/10.1007/s40257-020-00519-xCrossref PubMed Scopus (8) Google Scholar This study sought to investigate the likelihood of receiving RT after the treatment of DFSP with MMS versus that of receiving RT after treatment with WLE. We identified DFSP cases using the International Classification of Diseases for Oncology, Third Edition (ICD-O-3) 0-3 codes 8832 and 8833 in the National Cancer Database, the largest oncology database worldwide, which comprises >70% of all reported cancer diagnoses in the United States.3Bilimoria K.Y. Stewart A.K. Winchester D.P. Ko C.Y. The National Cancer Data Base: a powerful initiative to improve cancer care in the United States.Ann Surg Oncol. 2008; 15: 683-690https://doi.org/10.1245/s10434-007-9747-3Crossref PubMed Scopus (1441) Google Scholar Patients with prior or multiple cancer diagnoses were excluded. Clinicodemographic information was extracted for primary cases diagnosed between 2004 and 2017 that received treatment at the reporting facility, were diagnosed after the facility’s reference date, and reported at a follow-up time of >0 months. Missing data were imputed using multiple imputation by chained equations with 30 imputations. In each imputed dataset, MMS and WLE cases were matched using 1:1 nearest neighbor propensity score matching to account for baseline covariate differences, with propensity scores estimating the probability of treatment with MMS. The odds ratio (OR) of RT comparing MMS and WLE was calculated using logistic regression in each imputed dataset, and the estimates were combined using Rubin rules. Seven hundred sixteen DFSP cases were treated with MMS, and 3242 cases were treated with WLE (Supplementary Table I, available via Mendeley at https://data.mendeley.com/datasets/6jwcsr2s2j/2). The MMS and WLE cohorts received postoperative RT in 2.9% and 7.3% of the cases, respectively (unadjusted OR, 0.39; 95% CI, 0.24-0.62; P < .001). Among cases with negative margins, 1.8% (11/600) received RT after MMS compared with 5.8% (163/2806) after WLE (OR, 0.30; 95% CI, 0.16-0.56; P < .001). For cases involving the head and neck, RT was used in 8.3% (9/108) of MMS-treated patients and 17.2% (60/349) of WLE-treated patients (OR, 0.44; 95% CI, 0.21-0.91; P = .02). The median time to RT in the MMS cohort was 64.5 (interquartile range, 42.5-87.5) days compared with 57.5 (interquartile range, 41.0-89.5) days in the WLE cohort. An average of 692.3 MMS and WLE cases were matched across 30 imputed datasets, with absolute mean differences of <0.1 across baseline covariates in all imputations (Fig 1). After propensity score matching, the OR for RT after MMS compared with that after WLE was 0.51 (95% CI, 0.28-0.94; P = .03). The treatment of DFSP with MMS compared with that with WLE was associated with nearly half the likelihood of RT. Additionally, fewer patients received RT after negative margins with MMS versus with WLE. This finding may have been due to a variety of reasons, including surgeon or patient preference, practice patterns, concerning fibrosarcomatous degeneration on histology, concern regarding incomplete margin evaluation, or local recurrence. Other reports have described superior local control of DFSP after MMS versus after WLE.4Lowe G.C. Onajin O. Baum C.L. et al.A comparison of Mohs micrographic surgery and wide local excision for treatment of dermatofibrosarcoma protuberans with long-term follow-up: the Mayo Clinic experience.Dermatol Surg. 2017; 43: 98-106https://doi.org/10.1097/DSS.0000000000000910Crossref PubMed Scopus (75) Google Scholar,5Paradisi A. Abeni D. Rusciani A. et al.Dermatofibrosarcoma protuberans: wide local excision vs. Mohs micrographic surgery.Cancer Treat Rev. 2008; 34: 728-736https://doi.org/10.1016/j.ctrv.2008.06.002Abstract Full Text Full Text PDF PubMed Scopus (158) Google Scholar Because our analysis comprised matched MMS and WLE cases, our results suggest that treatment modality—rather than factors inherent to patient selection, such as tumor size, location, or insurance—was associated with different rates of RT utilization. The limitations include lack of database information on local recurrence, DFSP histologic variants (eg, fibrosacromatous, myxoid, and sclerosing), and surgical treatment rationale of the cases. First-line surgical treatment with MMS may reduce the need for RT and its associated morbidity. Dr Garg is an advisor for AbbVie, Aclaris Therapeutics, Anaptys Bio, Aristea Therapeutics, Boehringer Ingelheim, Bristol Myers Squibb, Incyte, InflaRx, Insmed, Janssen, Novartis, Pfizer, UCB, and Viela Biosciences; receives honoraria; and receives research grants from AbbVie, UCB, and National Psoriasis Foundation. Drs Yan, Elias, and Sharon and Authors Duvvuri and Strunk have no conflicts of interest to declare.