Linear accelerators have dramatically improved radiotherapy, enabling to treat patients faster and more precisely with higher doses of radiation. The technology allows to perform more efficient treatments, that notably reduce severe toxicity in prostate cancer, a Spanish radiation oncologist showed at the Triangle meeting last January in Spain.
Radiotherapy imaging was implemented a few years ago with cone beam computed tomography (CBCT), to acquire images and adjust the machine before applying radiation to the patient. The technique helped, but it had limitations, according to Felipe Couñago, Clinical Director and National Research Leader at Genesiscare Spain, who presented his work to the audience gathered at the luxurious Melia Castilla Hotel in northern Madrid.
‘It didn’t have the resolution of a CT scan, and we couldn’t see what was happening during the session, but we were happy,’ he said. ‘Then a revolution came with MR linear accelerators.’
MR linear accelerators are magnetic resonance-guided machines that use different photon energies to treat patients with cancer. Radiation oncologists have used these machines for a few years now, to contour, plan and treat by seeing exactly the region being treated, Couñago explained.
‘You can see how the organs at risk move, and if the tumor moves out of the area you programmed, the machine stops automatically, so as not to create toxicity,’ he said. ‘This precision allows us to treat with high doses of radiation tumors that we couldn’t treat before, such as pancreatic cancer or an ultra-centered tumor in the lung, in just a few days.’
Couñago and his team have worked with the Viewray MRIdian® for the past six months in over 60 patients, and they are the first team to use the equipment in Spain. In prostate cancer, the researchers have found that the technique greatly improves patients’ quality of life.
‘We have a level of evidence 1, which is authorized in Phase III studies, that shows significant benefits,’ he said. ‘Rectal incontinence goes down from 10% to 0%, and urinary toxicity from 40% to 20%. It’s just another league.’
A dream come true
Another benefit with the equipment is that it requires the presence of a physician and a physicist on top of the two technicians. ‘It looks like an operating room. The team has to have a re-contouring of the patient according to the present anatomy, and replan and control the movement,’ he explained.
The machine enables to treat patients in fewer days than traditional equipment, with 30-minute sessions for prostate cancer and 45-minute sessions in pancreatic cancer. ‘It’s the ideal machine to treat prostate cancer in five days,’ he said.
Pancreatic cancer, liver metastases, kidney cancer, adrenal metastases, retroperitoneal lymph node metastases, and high risk lung cancer such as ultra central lung cancer, could be additional applications.
Every patient could benefit from the equipment, he believes. ‘As physicians, it creates a certain conflicts of interest when we see that a patient cannot be treated with this machine because of cost issues,’ he said. ‘It is our preferred machine for treating patients.’
Few centers in Spain can actually afford the equipment, which costs three to four times the price of a conventional machine. ‘That’s a big limitation, it’s not being covered by the insurers of the patients we treat. But it’s still the best for radiation oncology.’
The machine enables to perform treatments that otherwise cannot be done, he insisted. ‘It was the dream of any oncologist to be able to treat while we see.’
Future developments will focus on providing more efficiency, with more data on tumor control. ‘The future is to be less invasive and treat patients faster. Instead of five sessions, we will only need two, so that the patient can go home quickly. The future trend is to reduce discomfort the patient as little as possible, so that he can go on with his life,’ he concluded.
Felipe Couñago is a radiation oncologist and the Clinical Director and National Research Leader at Genesiscare Spain. He specializes in genitourinary tumors and lung cancer. He has published more than 110 scientific articles in indexed journals. Up until June 2023, he was the Coordinator of the Spanish Lung Cancer Group (GOECP) of the Spanish Society of Radiation Oncology (SEOR).
