BACKGROUND: A previous study has shown that pentoxifylline in combination with vitamin E can reverse radiation-induced fibrosis. The aim of the present study is to investigate if the same drugs could prevent radiation-induced side-effects in women with breast cancer. PATIENTS AND METHODS: A randomised, placebo-controlled, double-blind, parallel group trial was performed. Women with breast cancer were treated for 12 months with 400 mg pentoxifylline t.i.d. or placebo, in combination with 100 mg vitamin E t.i.d., starting 1-3 months after the completion of radiotherapy. The primary end-point was passive abduction of the shoulder, and the secondary end-point was difference in arm volumes. The trial is registered on the ISRCTN.org website, number ISRCTN39143623. RESULTS: 83 patients were included in the study; 42 in the pentoxifylline+vitamin E group and 41 in the placebo+vitamin E group. Both treatments were generally well tolerated. Seven patients were withdrawn from the treatment due to disease progression; four in the pentoxifylline group and three in the placebo group. At inclusion, patients had impaired passive abduction of the shoulder. During treatment, both the groups improved significantly. Median improvement from baseline was 3.7 degrees (p=0.0035) on pentoxifylline and was 9.4 degrees (p=0.0041) in the placebo group, but no difference between the groups was detected (p=0.20). Arm volumes increased over time in the placebo group (1.04%), but not on pentoxifylline (0.50%), and differed significantly between the groups (p=0.0172). CONCLUSIONS: The combination of pentoxifylline and vitamin E was safe and may be used for the prevention of some radiation-induced side-effects.