This is a multicenter, randomized, open label phase lll trial to assess whether preoperative chemotherapy, as an adjunct to curative-intent surgery, improves the prognosis of high risk DDLPS (dedifferentiated Liposarcoma) and LMS (Leiomyosarcoma) patients as measured by disease free survival.

After confirmation of eligibility criteria, patients will be randomized to either the standard arm or experimental arm.

The primary objective of this phase III study is to evaluate whether the combination of lurbinectedin plus doxorubicin given as first line treatment for metastatic leiomyosarcoma (LMS) prolongs the progression-free survival (PFS) by Independent Review Committee (IRC) when compared to doxorubicin administered as a single agent.

The purpose of this study is to evaluate the investigational oral drug AMXT 1501 in combination with oral eflornithine (DFMO). An investigational drug is one that has not been approved by the U.S. Food \& Drug Administration (FDA), or any other regulatory authorities around the world for use alone or in combination with any drug, for the condition or illness it is being used to treat.

The goals of this part of the study are:

* Establish a recommended dose of AMXT 1501 in combination with DFMO
* Test the safety and tolerability of AMXT 1501 in combination with DFMO
* To determine the activity of study treatments chosen based on:
* How each subject responds to the study treatment
* How long a subject lives without their disease returning/progressing

The trial will use neoadjuvant hypofractionated radiotherapy followed by surgical resection in the treatment for soft tissue sarcoma. It will allow patients to be treated over a shorter course (5 or 15 days of radiation) compared to the traditional 5 week regimen. It is proposed that this will be possible without increasing the risk of wound complication or local recurrence compared with a traditional 5 week course of pre-operative radiation.