Serum level of the extracellular domain of HER-2 (ECD/HER2) has been suggested to be a tumor marker in breast cancer. The aim of this study was to assess the prognostic value of baseline level of ECD/HER2 and changes in levels over time in children and adults with osteosarcoma during chemotherapy.

Materials and methods: We analysed 33 newly-diagnosed osteosarcoma patients treated at the Department of Paediatric Oncological Surgery of the Institute of Mother and Child, Warsaw, Poland between 2005–2008. Patients characteristics: age 8–18 years (median 15); staging at diagnosis: disease localised (18) and dissemination (15); disease progression (13); deaths (6). Follow-up: 8–37 months (median 19). ECD/HER2 was measured in 118 serum samples using a validated ELISA kit: at the time of diagnosis (1), after preoperative chemotherapy (2), 2 weeks after surgery (3) and 3–6 moths after surgery (4).

Results: The baseline level of ECD/HER-2 in serum ranged 3.8–34.4 ng/mL (median 5). The elevated baseline ECD/HER2 was associated with decreased progression free survival (ECD/HER2 ng/mL> 5 vs ECD/HER2 ng/mL≤5: 44% vs 77%; p=0.039) and decreased overall survival (ECD/HER2 ng/mL> 5 vs ECD/HER2 ng/mL≤5: 69% vs 94%, p=0.115). The concentration of ECD/HER2> 6 ng/ml during treatment (specially postoperative chemotherapy) was associated with early disease progression (p=0.095).

Conclusions: The high level of ECD/HER2 at the time of diagnosis may be a marker of poor prognosis in osteosarcoma. Additionally, we suggest that changes of this marker concentration over time could be helpful for treatment monitoring.