Long‐term follow‐up of a prospective, double‐blind, placebo‐controlled randomized trial of clodronate in multiple myeloma

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Abstract
Oral clodronate (1600 mg/d) has been shown to significantly reduce the incidence of skeletal complications in multiple myeloma. Preliminary analysis of a double‐blind placebo‐controlled trial of this treatment indicated that clodronate might prolong survival in patients without vertebral fractures at presentation. This issue was re‐examined after further follow‐up of the patients recruited into the Medical Research Council (MRC) VIth Myeloma Study. The trial examined the effects of clodronate on the natural history of skeletal disease in multiple myeloma; 619 patients were randomized between June 1986 and May 1992 commencing 15 d after the start of ABCM [adriamycin, BCNU (carmustine), cyclophosphamide, melphalan] chemotherapy or 43 d after ABCMP (ABCM + prenisolone); 535 patients who received clodronate or placebo were included in the analysis. The presence or absence of spinal fractures was assessed centrally from spinal X‐rays; long‐bone fractures were assessed locally. With a median follow‐up of 8·6 years, there was no overall significant difference in survival between the two treatment groups (O/E, χ2 = 0·78,P = 0·38). Among the subgroup of 153 patients with no skeletal fractures at presentation there was a significant survival advantage (O/E, χ2 = 7·52,P = 0·006) in favour of the 73 patients receiving clodronate, with median survivals being, respectively, 59 months (95% CI 43–71 months) and 37 months (95% CI 31–52 months), and 5‐year survivals being 46% and 35%. The original analysis of this study shows that there is a benefit in taking 1600 mg clodronate daily for patients with myelomatosis to prevent the development of new skeletal disease. Bearing in mind the limitations of subgroup analysis, the present study indicates that treatment may prolong survival in patients without overt skeletal disease at diagnosis. These observations, however, require confirmation in prospective clinical trials.