Dermatofibrosarcoma protuberans (DFSP) is a locally aggressive intermediate malignancy.

The purpose of this retrospective analysis is to determine the efficacy of radiation therapy (RT) in local control of DFSP.

The recurrence-free survival (RFS) for 45 patients treated for DFSP at our institution was estimated and compared between surgery alone and postoperative RT groups.

Age range of the patients were in the third and fourth decades; males:females=2:1; most common site: anterior abdominal wall; tumours >5 cm in size in 75%; low grade in 77·8%; margins positive in 31·8% and <5 mm margins in 45·5%. Two-thirds of patients had at least one recurrence before presentation to our institution. RT dose was >50 Gy in 88% of patients. The patients treated with postoperative RT had poorer prognostic factors compared with surgery alone: they were males (17 versus 13 patients), and presented with high-grade tumours (5 versus 1 patients), multiple recurrences prior to presentation (25 versus 20 patients) and positive or <5 mm margins (22 versus 12 patients). Median follow-up for surgery alone group was 17 (1–152) months and for postoperative RT group, this was 54 (5–121) months. RFS at 5 years was 77·1% for surgery alone and 87·9% for postoperative RT group but was not statistically significant. The median time to recurrence was 4 years.

RT delays the time to recurrence in DFSP. RT improves the outcome of DFSP for recurrent tumours and with positive margins.