Liz Kenny of the Royal Brisbane and Women’s Hospital (Brisbane, Australia) gave her radiation oncologist’s take on the “120-odd-year” history of radiation therapy, how to plan it, and its delivery at the 2023 European Conference on Interventional Oncology (ECIO; 16–19 April, Stockholm, Sweden). “We—and you—stand on the shoulders of giants,” was one of her key take-home messages for delegates, specifying that these giants span many scientific disciplines and nations and have enabled the development of radiation oncology into the area of medicine it is today.
“Every single advancement in radiation therapy has been made hand-in-hand with physicists, industry, physicians, and radiation therapists across nations,” Kenny began. “The aim has always been to work out how we can maximally treat cancer tissue, while maximally protecting normal tissue.” In order to advance this area of clinical practice, Kenny elaborated on the “unwavering commitment to quality assurance” has also been necessary, alongside “our understanding of cancer biology and radiobiology” and “minimising short-and long-term complications, while knowing what they are”.
Kenny paid homage to Rod Withers (University of California, Los Angeles, USA), who she described as “a father of radiobiology who led us to understanding the relationship between the overall treatment time, total dose and the number of treatments. Lester Peters (University of Queensland Medical School, Queensland, Australia) was next in Kenny’s roll call of significant contributors to radiation oncology, as someone who spearheaded the need to embed quality assurance, in both trials and daily clinical practice, demonstrating the increased cure that this brings. Vincent Gregoire (Léon Béard Cancer Center, Lyon, France) was then attributed with the sage advice that intensity-modulated radiotherapy needs daily image guidance.
Computed tomography (CT) scanning was one of the advancements that Kenny credited with “revolutionising everything” in the field of cancer care. “The basic design of linear acceleration cannot really change,” she pointed out, “but how we manage it, how we rotate the treatment beams around patients, shaping the beams and modifying the dose coming through are all factors that can be altered as we treat. And, of course, computers, they have changed the world,” Kenny emphasised, before highlighting that planning systems, likewise, “have evolved apace” with “our ability to manage motion and reproducibility”. Machine learning also featured on Kenny’s list, which she explained “allows us to be 85% ready before we even start”. Then addressing the audience, she opined that “that has direct applicability in the [interventional radiology] world.
“We started off with chinagraphs, drawing on orthogonal films, and with two-dimensional planning, so we had a massive risk of geographic miss,” Kenny recalled. She commented that, even with the evolution to 3D planning, collateral damage was by no means a thing of the past. “So, with medical physicists we waged the war on normal tissue damage.” She charted the move from static to rotational beams, to changing the dose delivered in those beams, and changing the shape. “That is what allows me to treat someone’s very complex nasopharynx cancer, or ablate a patient’s lung cancer,” Kenny celebrated, all the while knowing “what outcome and side effects I expect, and what the cure rate has the potential to be”.
“Once we have made a decision to treat, the first step is planning, and planning is designating the right dose to the right place and determining what dose we will allow normal tissue to receive,” Kenny proceeded, referring to the capabilities nowadays for calculating the dose to different parts of the surrounding tissue ahead of delivery. However, she conceded that there may well still be plenty of scope for evolving diagnostic and functional imaging further.
Kenny called planning a “multistep process that involves a cast of thousands” to enable quality assurance at every step, from simulation, image fusion, to mapping out dose on every CT scan slice, to peer review, final acceptance of the treatment plan and then testing on a phantom “which is not so easy for [interventional radiologists]”. Planning and delivery can also be tailored according to whether the patient will be free breathing or assuming a deep breath hold or tracking the tumour during the delivery of treatment. Kenny supplemented, going on to detail that for stereotactic brain treatment, the immobilisation system with thermoplastic shells is “very exacting”.
Concluding, Kenny walked the audience through her radiation oncologist’s approach to delivering dose to patients, using image guidance: “There is no consolation for missing the target volume, no matter how sophisticated the technique of planning and delivery”. This, she summed up, by saying that “you have to be in the right place”. This is all the more critical when performing stereotactic ablative treatment in the brain, where there is a “0.02 to 0.05mm” tolerance.
“We have evolved in the last 40 or 50 years from 2D planning and treatment to 3D conformal planning to Intensity Modulated Radiation Therapy, all image driven. We can now sculpt and manipulate dose,” were among Kenny’s closing remarks. “It has been a wonderful journey, with our equipment following suit all the way through to helical devices and protons, with treatment rooms now looking like something out of Star Trek”. Kenny believes that machine learning through cloud-based sharing will enable continuous improvement in the field of planning and delivery of radiation therapies. “As imaging advances, we will become more accurate again and even now we are starting to be able to adapt during treatment.”
Liz Kenny is a professor at the University of Queensland and senior radiation oncologist at the Royal Brisbane and Women’s Hospital (Queensland, Australia).