The diagnostic and prognostic value of serum bone Gla protein (osteocalcin) in patients with recurrent breast cancer.

Serum bone Gla protein (S-BGP), a marker of bone metabolism, was measured in 60 patients included in a staging programme for recurrent breast cancer. Other diagnostic procedures comprised S-alkaline phosphatase (S-AP), bone scan (B-scan), bilateral iliac crest bone marrow biopsies, and radiological bone survey. The sites of recurrence were bone (61%), bone marrow (46%), soft tissue (52%), lung (13%), pleura (11%), liver (4%), and brain (2%). Radiology and bone biopsy served as key diagnoses as to the presence or absence of bone metastases. The diagnostic efficiency of B-scan and S-AP was greater than that of S-BGP, and the result of BGP measurement was associated with neither extent nor number of bone metastases. However, the BGP values were significantly lower in patients who had visceral metastases, and the median duration of survival after recurrence was 13 months for patients with low S-BGP levels (= < 2.0 nmol l-1), compared to 18 months for patients with medium S-BGP values (2.0-2.9 nmol l-1), and 25 months for patients with high values (> 3.0 nmol l-1) (p = 0.19). Analyses of the simultaneous effect of univariate prognostic factors were performed using the Cox proportional hazards model. S-alkaline phosphatase (S-AP) and S-BGP were the only significant, independent prognostic factors.