Since therapy consequences could be as dangerous as the disease itself, our major goal and hope is to minimize the risk of a second cancer by following international protocols and keep updating the results. We hope this book has provided good information about etiology, proportion and mechanism of leukemia following previous cancer therapy, including which drugs and treatment methods are causing it the most, and also the techniques for early detection and the best and safest ways for treatment including a new future promising drugs.The aim if this book is to show the importance of following the latest therapy philosophies and approaches - as we will see, we could avoid the consequences from just modifying the regimen and to put many cases in comparison as a first step to conduct studies at this topic in our country.