SP29 The Significance Of OOPS Lesions Professor Peter F.M. Choong MBBS MD FRACS FAOrthA University of Melbourne Department of Surgery, St. Vincent’s Hospital Department of Orthopaedis, St. Vincent’s Hospital Melbourne Bone and Soft Tissue Sarcoma Service Peter MacCallum Cancer Centre pchoong@unime.b.edu.au Unintended excision of soft tissue sarcomas (STSs) outside expert tumor centers is common. Often these require wide re-excision to achieve adequate oncologic margins. This is a retrospective review of 463 consecutive patients with soft tissue sarcoma who presented to our centre comparing unintended versus planned excision with the goal of assessing the factors that controlled local recurrence (LR) and metastasis rate (MR). Two hundered and ninety two patients had their first-time surgery at our institution, and 171 patients were referred after excision. Mean age of all patients was 55 years and male gender were more common (254 vs 209). Tumour size was smaller and location more superficial in those excised outside a tumour centre. Foot and groin lesions were more commonly excised outside a centre. Positive margins were more common in lesions excised outside a centre (102/171 vs 7/292). Despite smaller and more superficial tumours, complication of non-centre treatment was associated with similar amputation rates as centre treatment. More patients developed metastases (18/171 vs 16/292) and died of disease (53/171 vs 66/292) if treated outside a tumour centre. Quality of margins was associated with local recurrence. Quality of surgical margins was less when treated outside a tumour centre. The risk of death from disease was 3 times more common in patients treated outside a tumour centre. Unintended excision of STS has poorer outcome than planned excision. Therefore, patients with soft tissue masses should be managed by multidisciplinary team approach at specialized cancer centers.