Future directions in 3-d treatment planning and delivery: a physicist’s perspective

Abstract

I have been asked to describe the future advances that we are likely to see in radiation oncology treatment planning and delivery. I have chosen to look not too far ahead, but rather over the time period associated with the next generation of radiation oncology physicians and scientists, say by the year 2035. In my opinion, significant advances will be made by this new generation; however, they will be more evolutionary in nature, and not revolutionary. When I look back on my own career, I do recall some of my teachers and mentors questioning why I would want to pursue a career in medical physics applied to radiation oncology, thinking that physics contributions over the next 25 to 35 years would be minimal and that the next significant advancement would be made by biologists. In fact, some thought cancer was likely to be conquered within my (the next) generation. Similar predictions are now being made by some of my colleagues. I hope they are right; unfortunately, I do not think they are. There are still significant technological gains to be made by radiation oncology. In fact, radiation oncology is just now moving into a new and exciting era (which I will refer to as the three-dimensional radiation therapy [3DRT] era) as a result of the many technological advances made by this past generation. Modern medical imaging provides a fully 3-D volume representation of the cancer patient’s anatomy that allows the radiation oncologist to more accurately identify the tumor volume and its relationship with other normal tissues. The power of computers continues to increase rapidly (roughly doubling in speed every 18 months) while costs continue to decrease. These advances have spurred the development of computed tomography simulation (CT simulation) and 3-D radiation therapy treatment planning (3DRTP) systems that are likely to replace the conventional simulator and two-dimensional (2-D) dose planning systems as the standard of practice for radiation oncology within the first decade of the 21st century (1). Advanced computercontrolled treatment delivery systems that provide beam intensity modulated radiation therapy (IMRT) techniques for precise shaping of dose distribution are now in their first-generation developmental stage (2, 3). Improved IMRT systems will likely become the standard of practice during the second decade of this century. However, as these technological advances are occurring in radiation oncology, medicine overall is also entering a new socioeconomic era (which I will call the managed care era), in which lowering cost is a major driving force. Some will argue that the 3DRT era and the managed care era conflict and are not compatible. This is probably true today since 3DRT still needs a considerable amount of research and developmental (RD however,