10062 Background: The impact of treatment intensity on QoL of osteosarcoma patients is becoming increasingly important to assess. At present, no studies reflect QoL of osteosarcoma patients at diagnosis prior to surgery. EURAMOS-1 is an international randomized controlled trial to improve outcomes in osteosarcoma therapy. Concurrent with treatment, QoL is assessed as a secondary outcome measure across all participating countries through four oncology groups (COG, COSS, EOI, and SSG). Methods: For serial QoL assessment comparable QoL tools are used depending on group practice and patients' age. Questionnaires are the EORTC QLQ-C30 (self-rating) for all patients aged >=16y and the PedsQL or PEDQOL for patients aged <16y (self- and proxy). QoL is assessed 5 ±1 week after start of chemotherapy (T1), 10 weeks post surgery, 72 weeks and 142 weeks after diagnosis, respectively. T1 data was used to reflect QoL at diagnosis and analyzed in respect to age / gender and the instruments used. Results: As of October 20...