(P 472) ICONIC (IMPROVING OUTCOMES THROUGH COLLABORATION IN OSTEOSARCOMA). AN EARLY LOOK AT SURGICAL DATA

Objective: Osteosarcoma (OS) is a rare cancer with heterogeneity in presentation, treatment and outcomes. Surgery is essential for cure. Understanding variations and outcomes of surgery is essential to improving outcomes.

Methods: ICONIC (NCT04132895) is an observational prospective cohort study recruiting all UK patients with a new OS diagnosis with matched clinical, biological and PROM outcomes. This was a review of the available surgical data for patients recruited to February 2023.

Results: 219 patients have been recruited from 24 UK sites, median age 19 (range 3-83), 57% male. Femur (50%, 108/215), tibia/fibula (24%, 51/215) and humerus (9% 19/215) are the most common anatomical sites, though less usual sites are also represented (craniofacial (7%, 14/215), pelvis/sacrum (5% 10/215) and rib/chest wall (3%, 6/215)). Tumours in the pelvis, ribs and maxilla/mandible were associated with older age (Table 1).

Of 178 patients with surgical data available, 169 (95%) patients underwent surgery. Tumours in the pelvis/sacrum had the largest median diameter (129.5mm, compared to 120mm (0-900) overall), the lowest rate of resection (3/10 (30%) not resected) and the highest rate of amputation (3/7, 42%, compared to 36/178 (21%) overall). Amputation was performed in 1/13 (8%) humeral, 17/88 (19%) femoral and 14/45 (31%) of below knee tumours. The closest soft tissue margins were seen in the forearm and pelvis ( < 1mm margin in 2/4 (50%) and 3/6 (50%) respectively vs 23% overall). Overall 37/96 patients had a >=2mm margin and 37/96 had a good response to chemotherapy (>=90% necrosis) (Table 1).

Conclusion: Preliminary analysis demonstrates the acquisition of a rich surgical dataset. Results are broadly in keeping with other osteosarcoma studies but raise early questions about amputation rate and treatment variation across sites. Tumours in the pelvis and sacrum remain challenging. Biological, treatment and patient outcome data will further enhance this valuable resource.