Treatment strategies and outcomes of primary Myxofibrosarcomas in a large patients cohort.

Background: this study analysed primary myxofibrosarcoma (MFS) to investigate patient outcomes focusing on histopathologic margins and perioperative treatments.

Patients And Methods: data from consecutive patients affected by primary and localized MFS of the extremities or trunk wall who underwent surgery (2002-2017) were analysed. Local recurrence (LR), amputation rate, incidence of distant metastasis (DM), and overall survival (OS) were studied.

Results: Of 293 included patients, 52 (17%) patients received perioperative treatments and 54 (18%) had positive microscopic histopathologic margins (R1). Median follow-up was 80 months (IQR, 49-109). 5-yr CCI of LR was 0.12 (SE: 0.02). Status of histopathologic margins (P < 0.001), tumour malignancy grade (P = 0.018) and size (P = 0023) were independent prognostic factor for LR. Nine amputations (amputation rate: 3%) were performed (N = 1 for primary tumour; N = 8 for LR). Larger tumour size (P = 0.015) and higher grade (P = 0.025) were independent prognostic factor for DM. 5-year OS was 0.84 (95%CI 0.79-0.88). Patient age (P = 0.008), tumour size (P = 0.013) and malignancy grade (P = 0.018) were independently associated to OS. In the subgroup of patients who had a re-excision for a primary MFS (N = 116, 40%), the presence of residual disease was not associated with LR, DM, or OS.

Conclusion: in this study 5-year LR, DM and OS were 12%, 17%, and 84%, respectively. One in six patients had a positive surgical margin, which was a prognostic factor for LR, while DM and OS were predicted by tumour grade and size. Findings from this large patient cohort may set benchmarks for investigating new treatment options for MFS.