Randomization was performed through the proc plan procedure of SAS, using the method of randomly permuted blocks of 4. Within each block, the number of patients allocated to each of the two treatments was equal. Subjects who are eligible for randomisation will be given a subject number in consecutive order within blocks, and the investigational products packed corresponding to this number. The subject will be allocated to one of the two treatment groups, i.e. Thalidomide and placebo, according to a computer generated list provided by Pharmaceutical Co., Ltd. of Chang Zhou, China. If a subject discontinues from the study, the subject number will not be reused, and the subject will not be allowed to re-enter the study.