Glucocorticoids are the mainstay of treatment of idiopathic retroperitoneal fibrosis, but they often have substantial toxic effects. Several reports have suggested tamoxifen as an alternative to glucocorticoids. We compared the efficacy of prednisone with that of tamoxifen in maintainance of remission in patients with idiopathic retroperitoneal fibrosis. In this open-label, randomised controlled trial, we enrolled patients aged 18-85 years with newly diagnosed idiopathic retroperitoneal fibrosis at the Parma Hospital, Parma, Italy, between Oct 1, 2000, and June 30, 2006. After induction therapy with 1 mg/kg daily of prednisone for 1 month, the patients who achieved remission were randomly assigned to receive tapering prednisone (initial dose 0·5 mg/kg daily) for 8 months or tamoxifen (fixed dose 0·5 mg/kg daily) for 8 months. The sequence of randomisation (1:1), blocked in groups of two and four (with block size randomly selected), was generated by the trial statistician with a computer programme. After the end of treatment, the patients were followed up for an additional 18 months. Neither patients nor those giving interventions or analysing the data were masked to group assignment. The two radiologists who assessed CT and MRI scans were masked. The primary endpoint was the relapse rate by the end of treatment (month 8), which was analysed by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00440349. After induction therapy, 36 of the 40 enrolled patients achieved remission and were randomly assigned to treatment (18 per group). One patient (6) in the prednisone group and seven patients (39) in the tamoxifen group relapsed by the end of treatment (difference -33 [95 CI -58 to -8, p=0·0408]. The difference in relapse rate between the groups was sustained after the additional 18-month follow-up: the 26-month estimated cumulative relapse probability was 17 with prednisone and 50 with tamoxifen (difference -33 [-62 to -3, p=0·0372]). Cushingoid changes and grade 2 hypercholesterolaemia were more common in the prednisone group than in the tamoxifen group (p=0·0116 and p=0·0408, respectively). Prednisone is more effective in prevention of relapses than is tamoxifen in patients with idiopathic retroperitoneal fibrosis. Therefore, prednisone should be considered as first-line treatment for patients with newly diagnosed idiopathic retroperitoneal fibrosis. Parma University Hospital.
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