SPP1 and childhood malignant neoplasm: Osteopontin levels have been shown to correlate with direct O2 measurements, predicting disease progression and response to treatment in some adult cancers.29,30 The potential use of osteopontin as a biomarker has been demonstrated in childhood cancers, such as acute lymphoblastic leukaemia (ALL), malignant gliomas31 and osteosarcoma,32 although further investigation is required for clinical use.