Neoadjuvant radiation in primary extremity liposarcoma: correlation of MRI features with histopathology.

ABSTRACT

OBJECTIVE: To evaluate MRI features of response of primary extremity liposarcoma (LPS) to neoadjuvant radiation therapy (RT) with histopathologic correlation. METHODS: In this IRB-approved study including 125 patients with extremity LPS treated with neoadjuvant RT from 2000 to 2013, MRI of the primary tumour in 18 patients (5 pleomorphic LPS, 13 myxoid LPS) before and after RT were reviewed by two radiologists by consensus. Histopathology of the surgical specimens was reviewed by a pathologist with expertise in sarcomas. RESULTS: In the pleomorphic LPS cohort, 3/5 tumours increased in size; 3/5 decreased in enhancing component; and 3/5 increased in peritumoral oedema, intratumoral haemorrhage, and necrosis. In the myxoid LPS cohort, 12/13 tumours decreased in size, 8/13 decreased in enhancing component, and 5/13 increased in internal fat following RT. Histopathology showed ≥50% residual tumour in 1/5 pleomorphic LPS and 2/13 myxoid LPS. Hyalinization/necrosis of ≥75% was noted in 4/5 pleomorphic LPS and 11/13 myxoid LPS. Cytodifferentiation was noted in 1/5 pleomorphic and 9/13 myxoid LPS. CONCLUSION: While pleomorphic LPS showed an increase in size, peritumoral oedema, intratumoral haemorrhage, and necrosis on MRI following neoadjuvant RT, myxoid LPS showed a decrease in size and enhancement with an increase in internal fat. KEY POINTS • Pleomorphic LPS commonly increase in size and necrosis on MRI following RT. • Myxoid LPS commonly decrease in size and enhancement on MRI following RT. • Myxoid LPS often increase in fatty component on MRI following RT.