(P 218) NEOADJUVANT CHEMOTHERPAY AND RADIATION DECREASES TUMOR SIZE, VIABILITY, AND RECURRENCE IN MULTIPLE LIPOSARCOMA SUBSETS

Objective: Soft tissue sarcomas are a diverse group of cancers derived from mesenchymal cells that comprise less than 1% of cancers. Liposarcomas (LPS) are one of the most common types of soft tissue sarcomas and arise from lipocytes of soft tissues with different subgroups: well-differentiated (WDLPS), dedifferentiated (DDLPS), myxoid/round cell (MRCLPS), and pleomorphic (pLPS). Surgical resection is the mainstay of treatment for LPS; however, the roles of neoadjuvant radiation (na-RT) and chemotherapy (na-CT) are less clearly defined, particularly in intermediate/high grade LPS. In this study, we sought to understand how neoadjuvant treatments (NAT) administered affected outcomes of patients with localized non-well-differentiated LPS.

Methods: Using Vanderbilt University Medical Center’s Research Derivative, we identified patients with non-WDLPS who underwent resection of their primary tumor and were considered for neoadjuvant therapy from 01/2010 to 05/2022. Tumor characteristics and patient outcomes including margin status (PM), local recurrence (LR), and distant recurrence (DR) were assessed.

Results: 79 evaluable patients with DDLPS (43), MRCLPS (25), and pLPS (11) who underwent resection were identified (Table 1). Mean age was 57 years, 92.4% were white, 60% were male. 49% of patients had extremity tumors, 48% were intrabdominal or intrapelvic (IA/IP), 2% were in the chest or abdominal wall (CW/AW), and 1% were in the head or neck (H/N). 40 (51%) patients did not receive neoadjuvant therapy (no NAT), 27 (34%) received na-RT, and 6 (7.5%) patients received na-CT, and 6 (7.5%) received both na-RT and na-CT. 34 (43%) of patients had PM, 34 (43%) had LR, and 29 (36%) had DR. 24 (63%) of IA/IP tumors, 9 (23%) of UE/LE tumors, and 1 (100%) of H/N tumors had PM at resection. 20 of 34 (59%) of patients with PM had LR and 16 (47%) had DR.

27 patients (13 DDLPS, 9 MRC, 5 pLPS) received na-RT alone. Median tumor size was 15.5 cm pre-NAT and 15.8 cm post-NAT. Median MRCLPS tumor size was 14.7 cm pre-NAT and 13 post-NAT. Median viable tumor was 100% pre-NAT and 45% post-NAT: DDLPS 90% and 70% viable pre- and post-RT; MRC 100% and 10%; pleomorphic 100% and 30%. 33.3% had PM, 37% had LR, and 40.7% had DR.

6 patients (2 DDLPS, 2 MRCLPS, 2 pLPS) received na-CT alone. Median tumor size was 6.6 cm pre-NAT and 8.5 cm post-NAT. Median viable tumor was 100% pre-NAT and 60% post-NAT. 6 patients (1 DDLPS, 5 MRCLPS) received na-CT and na-RT. Median tumor size was 9.3 cm pre-NAT and 3.0 cm post-NAT. Median viable tumor was 90% pre-NAT and 2.5% post-NAT: DDLPS was 100% and 90% viable pre- and post-NAT; MRC was 100% and 2.5% viable pre- and post-NAT. 3 patients with MRC who received na-CT and na-RT had pathologic complete response (pCR). 1 MRC patient had PM and LR. 1 DDLPS patient had DR.

Conclusion: NAT was given to a higher proportion of patients with MRCLPS or pLPS. IA/IP DDLPS and MRCLPS tumors had the highest proportion of PM. NAT reduced the number of patients with positive margins at resection across treatment modalities. In patients receiving na-RT alone, changes in tumor size did not reflect changes in tumor viability pre- and post-NAT. Patients who received both na-RT and na-CT had reductions in tumor size and viability. Na-RT alone or in combination with na-CT was associated with a decreased LR and DR while na-CT alone was associated with an increased LR and DR. MRCLPS patients treated with na-RT and na-CT had multiple pCRs and had fewer PM, LR, and DR compared with MRCLPS treated with either modality alone.