Radiation Oncology in 21st century – Changing the paradigms

The developments in the field of Radiation Oncology are revolving around understanding of tumor biology, radiation effects, technology for visualization of tumor, and delivery of radiation in a planned manner. In past few decades there has been tremendous development in the field of imaging with addition of magnetic resonance and metabolic imaging. Treatment planning systems are made robust to make the complex planning fast and accurate. Use of multileaf collimators (MLCs) for alteration in beam pathways in three-dimensional conformal radiation therapy (3D-CRT) has become the minimum standard in radiation therapy. Inverse planning with allocating dose constraints to organs at risk (OAR) producing intensity-modulated radiation therapy (IMRT) has shown its benefits in numerous dosimetry and clinical studies. These developments in imaging and computer technology have also been utilized during execution of treatment. Daily variations in patient positioning, organ motion inside body, along with respiratory movements are now managed with the help of image-guided radiation therapy (IGRT). All these developments in the field of Radiation Oncology are aimed at reducing margins around tumor, delivering optimum radiation dose to tumor allowing minimum dose to the organs in close vicinity. Benefits of these developments are proven beyond doubt in some situations like head and neck cancers, prostate cancer, early stage non-small cell lung cancers and many others. Volumetric modulated arc therapy (VMAT) has potential to highly conformal radiation within few minutes. These technologies and their impact on present day practice of Radiation Oncology are discussed.