The general A+B designs with dose de-escalation. There are A patients at dose level i.
(1) If less than C/A patients have dose limiting toxicity (DLTs), then the dose is escalated to the next dose level i+1.
(2)If more than D/A (D \(\ge\) C) patients have DLTs, then it will come back to dose i-1.If more than A patients have already been treated at dose level i-1, it will stop here and dose i-1 is the MTD. If there are only A patients treated at dose i-1, then Bmore patients are treated at this dose level i-1. This is dose de-escalation. The de-escalation may continue to the next dose level i-2 and so on if necessary.
(3)If no less than C/A but no more than D/A patients have DLTs, B more patients are treated at this dose level i.
(4)If no more than E (where E \(\ge\) D) of the total A+B patients have DLT, then the dose is escalated.
(5)If more than E of the total of A+B patients have DLT, and the similar procedure in (2) will be applied.