Transiliac undecalcified bone biopsy specimens were taken after tetracycline double labeling from 14 patients with radiologic evidence of osteosclerotic metastases from prostatic carcinoma. The histomorphometric analysis showed an increased trabecular bone volume in all patients, and in seven morphologic and dynamic evidence of osteomalacia (Group 1). The seven other patients demonstrated an extension of apposition surfaces without evidence of osteomalacia (Group 2). Group 1 was different from Group 2 in terms of a greater increase in serum alkaline phosphatase and a lower urinary calcium. In four Group 1 patients, a second bone sample taken after two to six months of treatment with vitamin D and calcium provided evidence of improving osteomalacia. The high incidence of osteomalacia in osteosclerotic metastases of prostatic origin appears to be the result of the increase in bone formation induced by prostatic cells, and the unability to satisfy the high calcium demand for new bone.

In order to quantify bone changes which occur in multiple myeloma, undecalcified transiliac bone biopsies from 118 myelomatous patients were analysed by histomorphometric methods. Osteoclastic resorption surfaces were increased compared with controls, and the number of osteoclasts/mm2 of bone section was significantly greater in the areas massively invaded by plasma cells than in less invaded areas. The osteoid surfaces were also increased and the percentage of trabeculae that exhibited tetracycline labelling was also greater, indicating increased formation surfaces. However, reduced thickness of the osteoid seams and a low calcification rate, measured after tetracycline double labelling, suggests a reduced activity for each osteoblast. The mean trabecular bone volume was not reduced as compared with controls, but the biopsies showed a heterogeneous distribution of osteolytic and osteosclerotic areas. In the invaded areas, no major histomorphometric difference was found between patients receiving chemotherapy and untreated patients, demonstrating that if usual chemotherapies reduce the tumour mass, they do not improve histological bone lesions in areas still invaded by plasma cells.

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