Natural history of cancer of the breast. Probability of developing bone metastases

The incidence of bone metastases in 448 patients with breast cancer was evaluated. 374 out of 448 cases showed negative bone scan at initial clinical staging and were followed up during a period of at least 5 years with serial bone scans. The results of bone scans were compared on the basis of clinical stage (according to the International UICC classification), of lymph node involvement (groups N0, N + ) and of complementary therapy after surgery (radiotherapy v/s hormone-chemotherapy). Cumulative probability of bone metastases in breast cancer showed a linear trend with annual mean rate of 5% (1st yr 2%; 2nd yr 8%; 3rd yr 15%; 4th yr 22%; 5th yr 29%; 10th yr 59%). Statistical analysis in different clinical stages showed mild difference not statistically significant, neither in lymph node involvement (NO v/s N + ) nor in complementary therapy (radiotherapy v/s hormone-chemotherapy).