After a screening, which consists of pathology confirmation, physical examination, magnetic resonance imaging (MRI), body computed tomography (CT) scan, blood tests, and case analysis on Multidisciplinary Team (MDT) meeting, patient will be irradiated 5x5 Gy and after radiotherapy and then referred for surgery 6-8 weeks after the radiotherapy completion.

Myxoid liposarcoma has been reported to be more radiosensitive compared with other soft tissue sarcomas (STS). Response to preoperative treatment involves in decrease in tumor size, a large percentage in tumor necrosis (which according to some reports has a beneficial effect on the reduction of local recurrence rates) and also among other in a change in vasculature of the tissue.

Hypofractionation represents a variation of radiotherapy fractionation in which the total dose is divided into fewer fractions with an increased fraction dose. Such treatment may lead to additional biological effects when compared to conventionally fractionated radiotherapy (eg. vascular damage, increased immunogenicity, and antigenicity). The main advantages of hypofractionation are those related to the decreased overall treatment time what is more convenient for both patients and physicians, increased compliance and makes the treatment more cost-effective. Intriguing, such an approach may provide an additional benefit when treating non-radiosensitive tumors with a low alpha/beta ratio (eg. sarcomas).

The use of preoperative hypofractionated radiotherapy 5x5 Gy for five consecutive days, and then immediate surgery in patients with locally advanced soft tissue sarcomas showed in a published study a good local control rate, with a favorable amount of late toxicities. In this patient population, there were 22 patients with primary myxoid liposarcoma and the local control rate in this group was 86%.

In the proposed study we plan to increase the gap between the end of radiotherapy and surgery to commonly applied five weeks to better assess the changes occurring in the tumor after treatment and to evaluate the impact of longer treatment interval on reducing the proportion of early complications of treatment.

Inclusion Criteria:

• ≥ 18 years old;
• Eastern Cooperative Oncology Group (ECOG) performance status 0 - 2;
• pathologically confirmed diagnosis of localized, potentially resectable myxoid liposarcoma;
• primary tumor without previous treatment;
• extremity or trunk wall localization of the tumor;
• eligibility for limb-sparing surgery;
• >= 5cm in the longest diameter at imaging staging (MRI);
• adequate hematologic, liver, and renal function;
• women of childbearing potential must have a negative pregnancy test on the day of registration for study;
• female subjects who are breastfeeding should discontinue nursing prior to the first day of study treatment and during the whole radiotherapy treatment;
• no co-existing malignancy within the last 2 years except for adequately treated basal cell carcinoma of the skin or carcinoma in situ of the cervix;
• the absence of any psychological, familial, sociological or geographical condition potentially hampering compliance with the study protocol and follow-up schedule; those conditions should be discussed with the patient before randomization in the trial;
• before patient randomization, written informed consent must be given according to ICH/GCP.

Exclusion Criteria:

• history of radiation to the affected volume;
• previous or planned neoadjuvant chemotherapy;
• contraindications to radiotherapy, or surgery;
• metastatic disease.