(P 523) IN-BETWEEN SARCOMA: A CATEGORY OF HIGH RISK OF RECURRENCE AND POOR OUTCOME

Objective: Tumor depth as a prognostic variable (at either side of the fascia) has been withdrawn from the recent 8th. AJCC classification for soft-tissue sarcoma (STS). However, there are indications that infiltration of the fascia may confer a poor outcome to STS patients.

Methods: We identified limb and trunk wall STS involving the fascia either from inside out (of deep origin) or from outside in (from superficial origin), named In-Between Sarcoma (IBS). We compared retrospectively outcome of IBS patients to those with superficial (sSTS) and deep sarcoma (dSTS).

Results: Of 728 patients, 146 (20%) had IBS, 156 (21%) sSTS and 426 (59%) dSTS. IBS patients presented unfavourable characteristics with larger size (150 mm vs. 40 and 100 mm), more undifferentiated STS (42% vs 26% and 24%), more Grade 3 tumors (59% vs. 29% and 42%), respectively. Postoperative complications were 11.6% vs 3.9% and 8.2% (p = 0.04) and functional impairment 15.7% vs. 4.5% and 15.1% (p = 0.002), respectively.

Conclusion: Overall and metastases-free survival of IBS patients neared survivals of dSTS. Local recurrence-free survival of IBS vs. sSTS and dSTS were 81.1% vs 91.7 and 90.1% (p = 0.01).