Pattern of local recurrence after conservative surgery and radiotherapy for soft tissue sarcoma

Over the past three decades our centre has adopted a policy of conservative surgery followed by adjuvant radicaldose radiotherapy for medium-and high-grade soft tissue sarcomas. For all cases of local recurrence following this treatment we aimed to define the spatial relationship between sites of recurrence and the positions of the phase 1 and 2 radiotherapy volumes.

We identified 25 cases of local recurrence recorded on our soft tissue sarcoma database between 1986 and 1999 inclusive. We excluded patients with macroscopic residual disease following surgery. Most patients were treated with a phase I volume corresponding to the entire muscle compartment (50 Gy in 25 fractions over 5 weeks) and a phase II volume corresponding to the tumour bed (10 Gy in five fractions). Six of the patients were treated according to a hyperfractionated regimen.

For each case we reviewed the diagnostic imaging, planning radiographs and prescription sheets. We audited whether treatment had been given according to protocol and defined whether recurrence had arisen in the phase 1 volume, phase 2 volume or 'out of field'.

Four (16%) patients recurred within the phase I volume, 17 (68%) recurred within the phase II volume and four (16%) outside the irradiated volume including one marginal recurrence. In six patients there had been deviation from our radiotherapy protocol (usually unavoidable) including all three true out of field recurrences.

The majority of recurrences occur in the phase 2 volume. Prospective multi-centre data collection and, ideally, a prospective randomised trial are required to formulate an improved treatment policy with respect to radiotherapy margins and dose.