The stopping rules were determined following the method of Thall, Simon and Estey (JCO 1996) (20). The investigators assume that the apriori distribution for the toxicity rate can be described by Betal (1.3, 20) ie: mean toxicity rate = 0.05, 95% probability interval for toxicity rate is between 0.00 an d0.10. The trial would be stopped if the posterior distribution was such that :