(P 214) SIGNIFICANT TREATMENT RESPONSE IN PATIENTS WITH PRIMARY RESECTABLE EXTREMITY MYXOID LIPOSARCOMA RECEIVING NEOADJUVANT TRABECTEDIN AND RADIATION

Objective: Improved understanding of histology-specific sarcoma behavior and treatment has lead to improved disease-specific treatment. Historically all patients with extremity sarcoma received histology-agnostic neoadjuvant radiation or cytotoxic chemotherapy. More recently, Sanfilippo et al demonstrated that patients with myxoid liposarcoma who received neoadjuvant trabectedin combined with neoadjuvant radiation experienced significant rates of pathologic complete response at surgical resection. We now treat patient with extremity myxoid liposarcoma who are eligible for limb salvage with a similar protocol of neoadjuvant trabectedin combined with neoadjuant radiation. To date two patients have undergone this treatment regimen, clinical and pathological characteristics with short-term follow up of these patients are summarized.

Methods: Two patients with a primary resectable extremity myxoid liposarcoma received neoadjuvant trabectedin (initially: 1.5mg/m2 for six cycles) combined with neoadjuvant radiation (50 cGy in 25 fractions) during cycles five and six. Following recovery from neoadjuvant therapy patients were taken for surgical resection. Pathologic response and tumor cellularity of the initial biopsy specimen and of the resected specimen were defined by board certified sarcoma pathologists. Treatment and operative characteristics were recorded.

Results: The use of neoadjuvant trabectedin in two patients with primary resectable extremity myxoid liposarcoma is associated with significant treatment response ( < 5% and < 1% viable tumor) and substantial decrease in tumor size from preoperative imaging to final surgical specimen (10.5cm to 7.2cm and 9.7cm to 4.2cm). One patient required trabectedin dose reduction to 1.2mg/m2 for cycles 4-6 due to elevated liver enzymes. Neither patient has experienced short term local or distant recurrence. Both patients were able to work while receiving neoadjuvant therapy.

Conclusion: The use of neoadjuvant trabectedin and neoadjuvant radiation in patients with primary resectable extremity myxoid liposarcoma is associated with significant treatment effect with no impact on operative outcomes and no recurrence during short-term follow up. Longer follow up with more patients and comparison to historical control patients receiving neoadjuvant radiation alone is needed to understand the impact on long term recurrence and survival, but given the established association between pathologic complete response and overall survival this regimen is our current standard for patients who present with resectable myxoid liposarcomas with round cell features.