(P 307) IS RADIOTHERAPY NECESSARY FOR MANAGEMENT OF LOW GRADE MYXOID LIPOSARCOMA? A SYSTEMATIC REVIEW

Objective: Myxoid liposarcomas (MLS) are well understood to be radiosensitive soft tissue sarcoma variants. However, there is some institutional variability regarding whether low grade MLS is treated with perioperative radiotherapy. Although there has been increasing interest in neoadjuvant and adjuvant radiation for MLS treatment, the current National Comprehensive Cancer Network (NCCN) Clinical Practice Guidelines (CPG) do not support its use to treat low grade MLS. As such, a comprehensive and up-to-date evaluation of the existing evidence is essential to guide clinicians in making well-informed treatment decisions for low grade MLS. This systematic review aims to critically appraise the available literature on the efficacy of radiotherapy in the management of MLS. Furthermore, we will examine how grade and size impact outcomes among MLS patients treated with perioperative radiotherapy.

Methods: The PubMed, EBSCO Host, Cochrane Library, MEDLINE, and Google Scholar online databases were queried to identify studies published between January 1st, 1995 and March 1st, 2023 that evaluated radiotherapy among patients with MLS. After applying our predetermined inclusion and exclusion criteria, a final total of 18 articles were included for our systematic review. The Methodological Index for Non-Randomized Studies (MINORS) tool was used to assess the quality of included articles. Our analysis included a total of 18 studies reporting on 426 patients (Table 1). The mean (+/- standard deviation (SD)) MINORs score was 11.71 +/- 1.33 for non-comparative studies and 19.25 +/- 2.06 for comparative studies.

Results: Among included studies, there was agreement that pre-operative radiotherapy improved outcomes among patients with MLS (Table 2). Conversely, there was mixed evidence among cohorts receiving isolated post-operative radiotherapy or receiving both pre- and post-operative radiotherapy. A majority of included studies evaluating how tumor size impacted outcomes found that it did not have any effect on local recurrence, disease specific survival, or distance metastasis rates. A large majority of articles commenting on tumor grade indicated that a higher grade on French Federation of Cancer Centers (FNCLCC) grading system and a round cell component >5% were associated with a higher risk of local recurrence and metastases and a lower rate of overall and disease specific survival.

Conclusion: Our systematic review aims to help guide providers regarding the efficacy of pre-operative radiotherapy prior to surgical resection of MLS. Similarly, our analysis found that higher tumor grade was associated with worse outcomes while size did not appear to have an effect. It is important to note that there were limited numbers of high-quality studies in our review. Similarly, although included low grade MLS patients were treated with radiotherapy, there is a paucity of information regarding how radiotherapy impacts outcomes in isolated low-grade MLS cohorts. Given the trend in treating MLS, including low grade MLS, with radiotherapy, we have highlighted a gap in the existing evidence to determine the necessity of radiotherapy in low grade MLS patients. Future studies should evaluate the utility of radiotherapy in this cohort as well as in patients with low grade MLS less than ten centimeters.