(P 152) EVALUATING DIAGNOSTIC APPROACHES TO DERMATOFIBROSARCOMA PROTUBERANS: AN OPPORTUNITY TO REDUCE THE NUMBER OF INTERVENTIONS

Objective: Dermatofibrosarcoma protuberans (DFSP) is a rare soft tissue sarcoma that is difficult to diagnose due to its occult clinical presentation. The National Comprehensive Cancer Network Clinical Practice Guidelines recommend incisional, punch, or core needle biopsy, but there are limited data regarding the optimal diagnostic approach. The objectives of this study were to characterize current practices of DFSP diagnosis and to compare clinical outcomes based on chosen biopsy technique.

Methods: Data were retrospectively collected for adult patients who underwent surgical resection for the initial presentation of a DFSP lesion between 2003 and 2021 at 11 institutions in eight countries. Patients were grouped according to biopsy type: excisional biopsy versus preoperative biopsy, which included incisional, punch, and core needle biopsies. Demographics, tumor characteristics, treatment strategies, and outcomes were explored with descriptive statistics and univariable analyses.

Results: The whole cohort included 366 patients, 86.5% (N=315) of whom were treated at academic centers. The median age was 42 (IQR 31-54) years, and 53.6% (N=195) were male. A DFSP diagnosis was made in 91.6% (N=318) of patients based on biopsy procedure. Among these, 50.4% (N=172) were excisional, 25.5% (N=87) were incisional, 16.1% (N=55) were punch, and 7.0% (N=24) were core needle biopsies. Notably, DFSP was an incidental pathologic finding in 21.7% of all cases (N=78), and preoperative imaging was used to characterize tumors 56.1% of the time.

Patients were then compared according to biopsy type (excisional biopsy, N=172; preoperative biopsy, N=166). The proportion who underwent excisional biopsy was relatively stable during the study period according to a time-trend analysis (p=0.057). There were no differences between groups in terms of patient sex, disease presentation, or disease location. Excisional biopsy was most frequently performed by general surgeons (49.1%), as compared with dermatologists (21.0%), surgical oncologists (4.8%), or primary care physicians (1.2%). Compared with excisional biopsy patients, patients who underwent preoperative biopsies were likely to be younger (median 43 (IQR 36-55) vs 39.5 (IQR 29-53) years, p=0.031) and treated at academic institutions (80.1% vs 91.1%, p=0.009) with their biopsies performed by dermatologists (21.0% vs 44.0%, p< 0.001). Regardless of biopsy type, groups were similar as far as planned circumferential margins at first resection, final pathology, and specimen size. Although excisional biopsy patients required a greater median number of excisions to clear disease (2 vs 1) and were less likely to achieve R0 margin status after the index resection (59.2% vs 77.2%, p< 0.001), final R0 rates were comparable in both groups (93% excisional biopsy versus 87.5% preoperative biopsy, p=0.10). Recurrence was altogether rare but was more frequently observed after excisional biopsy than preoperative biopsy (8.1% vs 4.1%, p>0.05).

Conclusion: In this international, multicenter collaborative, diagnostic approaches to DFSP were quite varied. Excisional biopsy appears to be a reliable diagnostic tool, however, its association with positive surgical margins and multiple excisions may limit its benefit and introduce potential morbidity. Efforts should be made to unify diagnostic approaches to mitigate extraneous procedures and improve outcomes.