Individualized neo adjuvant external beam radiotherapy for rectal cancer: From concept to clinical implementation The ART to adapt

The standard of care for intermediate and locally advanced rectal cancer is a multimodality treatment of chemotherapy, surgery and radiotherapy. Radiotherapy improves local control and/or improves chances of a complete resection but comes at the cost of increased toxicity.
This thesis starts with defining appropriate population based planning target volume (PTV) margins for a single fixed treatment plan for rectal cancer. It subsequently explores more flexible concepts than a single fixed treatment plan in the form of multiple a-priori designed treatment plans to reduce the PTV margins and it describes the translation of this concept into clinical practice. This thesis concludes with the design and clinical implementation of online adaptive radiotherapy, a technique to adapt the treatment plan to the daily anatomy. In short, this thesis describes the road from 3D conformal radiotherapy to online adaptive radiotherapy for the treatment of rectal cancer.