Abstract
Myxoid or Myxoid Round Cell liposarcoma (MLS) is a mesenchymal malignancy with adipocyte differentiation accounting for 15–20% of liposarcomas and 5% of all adult soft tissue sarcomas (STS). Like other STS, treatment of MLS is generally by wide surgical resection in conjunction with radiotherapy and this approach is associated with low rates of local recurrence [1]. However, most MLS are located between muscles so wide local excision(WLE) can be quite morbid with adverse functional results. MLS are known to be extremely sensitive to radiotherapy which has led to development of treatment protocols utilizing neoadjuvant radiation. Given the radiosensitivity of MLS, we hypothesize that resection with marginal margins (1mm) does not result in higher rates of local recurrence or disease-free survival if performed following pre-operative radiotherapy.
We identified all patients with localized MLS who underwent preoperative radiation and surgical resection between January 2000 and January 2018 from a prospectively collected sarcoma database. We calculated the ellipsoid tumour volume(ETV=h x w x d x ()) at diagnosis and after radiation, and documented the necrosis percentage of the tumour and margin status following resection based on histological analysis [2]. Marginal resection was identified by the operative report describing no or only very minimal resection of muscle surrounding the tumour, and a negative surgical margin 0.1cm/1mm as defined histologically. In comparison, WLE was defined if the operative note described an attempt to remove the tumour with a cuff of surrounding muscle, and the final histology reported a negative margin 0.1cm/1mm which included skeletal muscle. The third group for analysis included patients with positive resection margins.
There were 91 patients with MLS of mean age 48 years (range 18–88) with 69% male and 31% female. The mean pre-radiotherapy ETV was 507cm3(16.1cm3 to 6961cm3) and decreased to 361cm3(8.7cm3 to 5695cm3) following radiation, with an average percentage reduction in ETV of −45%(+129%to-99%). Mean patient follow-up was 7.3 years (0.2–18) with no differences between margin groups(p=0.284). Only 10(11%) patients had positive margins, of which 43(47%) underwent marginal resection and 38(42%) WLE. Overall the mean necrosis as measured histologically following preoperative radiation was 69% (range 0–100%) with no differences between the 3 resection groups(p-0.151). Similarly, there was no significant difference in reduction in mean ETV between the three resection groups(p=0.311), there was no significant difference between the three treatment groups in 5-year LR-free survival (p=0.469), metastasis-free survival (p=0.841) or overall survival (p=0.873).
Most patients with MLS experienced significant reduction in tumour size and necrosis following preoperative radiation. We found no differences in the risk of local recurrence or survival based on the type of surgical approach for patients with MLS. Based on these results, we conclude that MLS can be safely removed by marginal resection following preoperative radiotherapy with high rates of local tumour control. Even following a positive margin resection, local recurrence remains uncommon after preoperative radiation. A marginal surgical approach for patients with MLS reduces the need for major muscle resection and is associated with improved functional outcomes with less complications.
