Log (hazard ratio) values in overall survival model depicting the role of interaction between cytogenetic abnormalities and thalidomide. The presence of CA has a significant adverse effect on OS in control group (P < .001), whereas the adverse effect in the thalidomide group is not significant (P = .06). Thalidomide has no effect on OS in patients with no CA (P = .87) but has a significant beneficial effect on OS in patients with CA (P = .008).