Biochemical assessment of bone disease in multiple myeloma.

In patients with multiple myeloma, with moderate and severe bone disease, the urinary hydroxyproline excretion was disproportionately elevated with respect to the activity of bone isoenzyme of alkaline phosphatase when compared with the relationship between the variables observed in 58 age- and sex-matched controls and in 50 healthy young subjects. A significant positive correlation was found between urinary hydroxyproline excretion and the clinical variables related to the extent of bone involvement in multiple myeloma (X-rays, patient's performance status, anaemia). In 9 out of 13 patients with moderate and severe bone disease the chemotherapy-induced remission was associated with a significant (p less than 0.05) rise in the activity of bone isoenzyme of alkaline phosphatase and decrease (p less than 0.005) in urinary hydroxyproline excretion. In successfully treated patients, the relationship between the biochemical variables indicated increased but proportionate extents of whole-body rates of bone formation and resorption. This was not the case in patients in whom no chemotherapy-induced remission was noted. The simultaneous evaluation of the activity of bone isoenzyme of serum alkaline phosphatase and urinary excretion of hydroxyproline improves the assessment of bone involvement in multiple myeloma and the efficacy of treatment.