Good question.
You will notice that more than 50% of the time, these breakouts never pullback. Breakouts without a pullback are very powerful and usually generate the biggest gains in percentage terms.
Unfortunately, it is simply too risky to chase them, at least for me. As a rule of thumb, if I see no pullback after a maximum of 10 to 15 bars (after the breakout), I simply look for another trading opportunity, for the simple reason that real, meaningful breakouts rarely spend that much time to return to the breakout line before resuming their initial move.