The concept of adaptive radiotherapy (ART) was proposed 20 years ago, and since then a variety of meth-odologies and techniques have been developed to accommodate different clinical requirements, including both online and of-fline plan adaptations. Compared with pre-treatment planning, plan adaptation involves more computational tasks and con-sequently has increased complexity and computational burden. While ART can benefit many cancer patients, challenges still exist in development and implementation of high-quality ART programs. In this short review, we will focus on the de-velopment of offline ART for lung cancer. We will also discuss the advantages and disadvantages of different clinical imple-mentations of ART.