(P 128) DYNAMIC HETEROGENEITY AMONGST LIPOSARCOMAS

Objective: This study aims to provide a comprehensive analysis of dedifferentiated liposarcoma cases discussed at our Sarcoma Multidisciplinary Team (MDT) meetings over a seven-month period. By examining the clinical characteristics, treatment modalities, and outcomes of these patients, we seek to enhance our understanding of the tumors behaviour and contribute to improved management strategies for this patient population.

Methods: We performed a retrospective study of all patients with dedifferentiated liposarcoma (histologically confirmed at our institution) discussed at our Sarcoma multidisciplinary team meeting in the last 7 months, between the 14th December 2023 and 13th June 2024. Statistical analysis was performed using SPSS. Categorical variables are presented as frequencies and percentages, and continuous variables as medians and interquartile ranges, or means and standard deviations for normal distribution variables. Normal distribution was verified using Shapiro-Wilk test.

Results: From the total number of 20 patients in this cohort, there was an even distribution among sexes. The mean age at diagnosis was 62-years-old (±14.7).
From the 20 patients diagnosed with dedifferentied liposarcomas, 15 (75%) patients’ initial biopsies were already dedifferentiated liposarcomas; while 4 (20%) were well differentiated and 1 (5%) had foci of dedifferentiation, all of these five dedifferentiated along the follow-up. Out of the total liposarcomas, 11 (55%) had no specific pattern, 3 (15%) were described as adopocytic and sclerosing, 2 (10%) as myogenic, 1 (5%) as myxofibrosarcoma, 1 (5%) as fusocelular and 1 (5%) as osteosarcoma.
Surgery was chosen as first line therapy (n =19; 95%) in all patients, except for one individual (5%) without performance status to tolerate a surgical intervention, to whom radiotherapy was offered. Subsequent treatments were required in half of the patients (n = 10; 50%), since the disease recurred frequently even after R0 surgery. Other treatment options chosen at latter stages were radiotherapy (n = 5; 25%), chemotherapy with doxorrubicine-ifosfamide (n = 4; 20%), doxorrubicin monotherapy (n = 1; 5%), gemcitabine-docetaxel (n = 1; 5%), gemcitabine monotherapy (n = 1; 5%), and brigimadlin (n = 1; 5%).
With a median follow-up of was 25.15 months (0.74-220.34), overall survival median was not reached. Disease free survival after first line surgery was 22.52 months (6.73-38.31). Ab initio dedifferentiated liposarcomas had shorter median disease free survival (16.1months) vs the one with foci of dedifferentiation (25.71 months) vs well differentiated (43.65months). Also, interestingly those without a specific pattern had better mean disease free survival (60.1months) than those described as adipocytic and sclerosing (26.6months), as fusocelular (26.2months), as myxofibrosarcoma (25.7 months), or as myogenic variants (14.2 months) and as osteosarcoma (3.9months).

Conclusion: Liposarcomas are dynamic tumors that transform throughout the course of the disease. Dedifferentiation and specific patterns of dedifferentiation including myogenic and osteosarcoma confer a bad prognosis, worse response to therapeutics and shorter disease free survivals.