To assess the relapse-free survival (RFS) and the factors influencing local recurrence in patients with desmoid fibromatosis (DF) treated at our centre and to determine the role of post-operative radiotherapy (RT) in improving local control.

A retrospective analysis of 51 patients treated for DF from January 2004 to December 2013 was undertaken. The RFS was calculated using the Kaplan–Meier curve. Univariate analysis was done to assess correlation with tumour size, site, the extent of surgery, margin status and adjuvant RT with RFS.

The median age was 28 years with a male:female ratio of 1:3. The most common location of the tumour was anterior abdominal wall (47%). The median tumour size was 10 cm. Wide local excision was done in most patients. Complete resection with negative margin was achieved in eight patients. Post-operative RT was indicated for 43 patients of whom 19 received RT. At a median follow-up of 37 months, RFS in the complete resection with margin negative group was 100%. RFS for the patients with positive or close margins who received RT was 79% and for those who did not receive RT, it was 87%.

Complete excision with negative margins gives the best local control in DF. The benefit of post-operative RT could not be ascertained.

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.