Defining the chemotherapy (CT) response in well-differentiated (WD) and dedifferentiated (DD) liposarcomas (LPS) of the retroperitoneum (RP): A tertiary referral cancer center experience.

10583 Background: WD/ DD LPS is the most common LPS subtype, predominantly arising in the RP. Surgery is the primary treatment, but recurrences are frequent. CT is usually reserved for unresectable cases and the reported RECIST response rate (RR) is 12% (Italiano et al. 2012). However, in our experience, RECIST does not capture morphological changes consistent with response on imaging. Our objective was to review RR to CT and describe radiologic patterns of response. Methods: Search of the tumor registry for patients (pts) with RP WD/DD LPS who received CT at MD Anderson Cancer Center from 2003-2013 yielded 48 pts. The pathology database registered 316 new pts with RP WD/DD LPS in the same time frame. Data was collected from the electronic charts and the Social Security Death Index. Here we report the results for the first 48 pts; updated analysis with RECIST and imaging characteristics by an independent radiologist will be presented at the meeting. Results: Of 48 pts, 40 had WD/DD confirmed on pathology ...