Radiation therapy for cancer is becoming increasingly complex, sophisticated and personalized. Behind the scenes for most patients hides an invisible team of medical physicists, radiation therapists, imaging technologists, radiation protection professionals and nurses.
It is a little understood backstage world.
Radiation therapy has been around for decades. Canada played a key role in the development of Cobalt 60 treatment in 1950s and ’60s, under the leadership of Sylvia Fedoruk. These treatment units were nicknamed the Cobalt bomb. Such early treatments crudely irradiated tumors and everything around them with wide beams and high doses. Ever since, radiation therapy advances have focused on reducing normal-tissue damage while still attacking the tumor.
Therapy devices are the key tool, most commonly linear accelerators or LINACs. They look like a CT machine but have treatment heads that move around the patient instead of the “doughnut” CT mechanism.
For patients, the first point of contact are the radiation oncologists, who weigh the risks and benefits of radiation therapy and develop treatment protocols: total radiation dose, number of sessions, fractions into which overall doses should be divided. Not least, they assess the risk to normal tissues in the therapy and consider this in the treatment protocol.
Approximately 70 per cent of cases are reviewed in dedicated quality assurance multidisciplinary rounds prior to treatment, says Rashmi Koul, Medical Director of the Radiation Oncology Program at Cancer Care Manitoba. Radiation oncology is specialized work, and there are only 584 currently credentialed physicians, according to the Canadian Association of Radiation Oncology.
The next step in most cancer journeys continues with a radiation therapist.
They do the heavy lifting in treatment, which starts with CT images and trial runs with patients to establish body positioning and, given the need for complete stillness as radiation pours in, the immobilization options.
Tools for precision placement include: permanent positioning skin markers, tattoos and rice-sized metal beads inserted under the skin. Most cases require custom plastic molds or form fitting pillows or mattresses that lock the patient in position on the treatment bed.
The future of external beam radiotherapy is about customizing therapy for each patient according to the type, size and location of the cancer.
In addition, modern LINAC machines can take CT-like images (kV cone beam CT) to ensure that the patient’s anatomy and tumor still match up to the original CT scan.
Radiation therapists are part of a broader set of technology professionals under the umbrella of the Canadian Association of Medical Radiation Technologists (CAMRT), which also includes CT, nuclear medicine and MRI imaging technologists. In 2021, about one quarter of Canada’s 11,000 registered technologists were radiation therapists.
Patients are commonly treated daily, and generally not on weekends, for one to eight weeks. Each treatment takes about 30 minutes. Patients get a new cone-beam CT scan before each treatment to ensure they are still properly positioned, and to ensure they have not lost enough weight to require a recast of the immobilization mold.
Further in the background and almost never seen by patients is a network of 460 radiation oncology medical physicists, most with their PhDs, who ensure radiation therapy machines are working properly.
Other team members include: radiation safety professionals who ensure that workers and the public are protected from radiation exposure; general imaging technologists and nurses who start IVs and help manage radiation-related side effects and allergic reactions to injections of imaging contrast dyes.
Looking forward, the future of external beam radiotherapy is all about customizing therapy for each patient according to the type, size and location of the cancer. The trend is to give fewer higher dose fractions to the tumor. This hypofractionation requires very precise control of the radiation beam, to the millimetre, says Boyd McCurdy, Head of Medical Physics, Cancer Care MB.
Some forms of hypofractionated therapy are so precise that they are thought of as a “radiation scalpel” and a few treatments can kill the cancer with a very high radiation dose. TomoTherapy, Edge and CyberKnife technologies provide such precise treatments called stereotactic body radiation therapy (SBRT) and most major centres offer some form of SBRT. Gamma Knife is a specialized form of precision therapy for head and neck tumors and is available in Edmonton, Winnipeg, Toronto and Sherbrooke.
As radiation therapy becomes increasingly sophisticated and personalized, the “behind the scenes” professionals need to be recognized as playing essential roles in caring for cancer patients undergoing radiation therapy.