Prognostic factors for skeletal relapse in breast cancer

Bone metastases and the strong interaction between osseous and metastatic cell populations require interdisciplinary thought and actions. If it were possible to interrupt the malignant dialogue between tumour and bone at an early stage, this might not only reduce the amount of bone destruction, but could also reduce the incidence of osseous metastases and remove the source of secondary metastases to other organs. Studies into the preventive effects of bisphosphonates are currently running or are planned. Most of these studies are in breast cancer patients with involvement of the axillary lymph nodes. The prognostic factors of lymph node status, tumour size and grading are better than none, but do not select patients at a high risk of skeletal metastasis. This would be much better done by using immunohistochemical methods to investigate the primary tumour for bone sialoprotein and parathyroid hormone-related protein (PTHrP). However, these methods are complicated, have not been validated in large numbers of patients and are not standardized. Serum tests for bone sialoprotein, PTHrP and collagen fragments are currently still under development and cannot be recommended generally. The clinical importance of tumour cells in the bone marrow has been demonstrated but is still only used at a few centres.