7.P.66 SOLITARY SKELETAL RELAPSE IN OSTEOSARCOMA: FINDINGS IN 38 PATIENTS FROM THE COOPERATIVE OSTEOSARCOMA STUDY GROUP (COSS)

Only few patients with osteosarcoma relapse with solitary skeletal lesions as only sign of recurrence. We used the COSS database to learn more about these rare occurrences. This report covers all patients with high-grade osteosarcoma of the limbs or axial skeleton registered into the COSS database between 1980 and 2003 who developed 1st recurrences as solitary osseous lesions distant from the primary tumour before 01/2005. Patient-, tumour-, and treatment-related variables and outcomes were evaluated. 38 patients (27 male, 11 female) developed solitary osseous recurrences a median of 2.1 years (range:.5 – 14.3) from primary diagnosis. Primary sites had been limbs in 36 and axial in 2, relapses involved axial sites (24), limbs (10), or craniofacial bones (4). Treatment for osseous recurrence included surgery in 28 patients, radiotherapy in 10, and chemotherapy in 27. After a median follow-up of 1.9 years (range:.1–21.2) from 1st recurrence for all 38 patients and 5.5 years (.3–21.2) for 16 survivors (10 of these in continuous 2nd surgical remission), 2- & 5-year overall and event-free survival probabilities were 55% & 34% and 34% & 27%, respectively. A long interval to recurrence (> 1.5 years) predicted for better outcomes (p 1st solitary skeletal recurrences of osteosarcoma seem to have a favourable outcome provided treatment includes complete surgery as part of multimodal therapy. Some presumed bone metastases may rather represent second primary osteosarcomas. The COSS studies that form the basis of this report were supported by Deutsche Krebshilfe.