Optimising Clinical Outcomes Following R1 Resection in Soft Tissue Sarcoma: An Evidence-Based Approach.

opinion statementMicroscopically positive surgical margins (R1) complicate 15-30% of soft tissue sarcoma (STS) resections and independently worsen local recurrence and overall survival, yet no randomised trial has targeted the R1 population; we recommend risk-adapted management directed by a multidisciplinary team at a specialist sarcoma centre. Decision-making should integrate histological subtype, tumour grade, anatomical site, margin context, and individualised prognostic risk estimated by validated nomograms such as Sarculator and PERSARC. Planned positive margins on critical anatomical structures, most often encountered in retroperitoneal sarcoma, do not mandate re-excision, as local recurrence rates approximate those of R0 resection, and management should proceed directly to histotype-tailored adjuvant radiotherapy where indicated. Inadvertent positive margins after unplanned or non-specialist excision carry a substantially higher local recurrence risk and warrant re-excision whenever secondary R0 is achievable without prohibitive morbidity, followed by adjuvant radiotherapy in high-grade or deep tumours. When further surgery is not feasible, adjuvant radiotherapy alone remains the standard adjunct and substantially reduces local recurrence in extremity STS. Adjuvant anthracycline-ifosfamide chemotherapy should be considered in patients identified as high-risk by validated nomograms, in whom R1 status is the strongest predictor of survival benefit. Active surveillance with structured imaging follow-up is a reasonable option for small, low-grade R1 tumours at sites of prohibitive re-excision morbidity. Referral to a specialist sarcoma centre before any initial intervention remains the single most impactful measure to reduce R1 incidence and optimise oncological outcomes and should be regarded as the overarching standard of care.