PURPOSE: Preoperative radiotherapy provides advantages in the management of retroperitoneal sarcoma (RPS). We describe our experience treating a cohort who underwent pre- and post-radiotherapy functional imaging with FDG-PET scan. METHODS AND MATERIALS: Consecutive patients presenting between January 1999 and December 2009 with a diagnosis of either primary or recurrent RPS were identified from the hospital patient record database using ICD codes, and cross-referenced with the completed radiotherapy course database. Those patients suitable for preoperative radiotherapy and surgery who underwent both pre- and post-radiotherapy FDG-PET were included. Exclusions included presence of metastatic disease, age under 18 years and/or paediatric histology, and treatment with palliative intent. RESULTS: Eleven patients were included, of whom six were male. Median age was 63 years (range, 38-78 years). The majority of patients had Stage T2b, high-grade disease. Ten patients were treated at initial presentation and one at first local recurrence. A malignant diagnosis was confirmed in all patients who underwent CT-guided core biopsy; a diagnosis of sarcoma was reached in 91%. Sensitivity of FDG-PET imaging was 100%. Metabolic partial or complete response did not correlate with change in tumour size, nor pathological response assessment. Pulmonary and hepatic metastatic disease was detected in one patient on post-treatment imaging. All patients in the cohort completed preoperative radiotherapy. There was no grade 3 or 4 toxicity. Sixty-four percent proceeded to radical resection. Complete macroscopic excision was achieved in all cases. There was no perioperative mortality. CONCLUSION: Combined therapy with preoperative radiotherapy and surgery has acceptable levels of toxicity. CT-guided core biopsy is an accurate means of confirming a diagnosis of RPS prior to definitive treatment. Utility of PET scan in the management of RPS is evolving and further investigation is warranted.