Duration of bisphosphonate treatment: results of a non-randomised study in patients previously treated with local irradiation for bone metastases from breast cancer.

PURPOSE: To assess whether disodium pamidronate (DP) once started should be given life-long in women with lytic bone metastases. PATIENTS AND METHODS: One hundred and three women with breast cancer who had at least one osteolytic lesion received 180 mg of DP as a 2-h intravenous infusion given every 4 weeks for a life-time, following local radiotherapy. After six cycles, 26 out of 103 patients (25%) refused to continue their bisphosphonate-treatment. Thus two groups were constituted: non-stop (group A) and premature discontinued (group B). The new skeletal complication free survival (NSCFS) was the primary endpoint verified during extramural review. Performance status, pain-score and biochemical markers were secondary endpoints.
RESULTS: Generally DP was well tolerated. At 36 months, the proportion of patients having had any skeletal complication was 54.5 and 84.6% in group A and B, respectively. The median time of NSCFS was apparently longer for group A. In group A, the pain score and the ECOG status were significantly lower, while the overall survival appeared to be longer. Multivariate analysis revealed age, nodal status and interruption of treatment as prognostic factors to NSCFS, with relative risk 1.05, 2.3 and 1.5 respectively.
CONCLUSION: Data concerning the suspension of new skeletal complications, as well as the apparent improvement of overall survival, pain score and ECOG status, suggest that the pamidronate-treatment should not be stopped once started. These results should be confirmed in a randomised trial.