Radiotherapy: Ongoing Development of a Cutting Edge Technique

The effectiveness of radiotherapy can undoubtedly be improved even further.

Aside from combining radiotherapy with another treatment (heat, chemotherapy/hormone therapy, precision medicine etc.), various potential new treatments are currently being studied. One of these is “FLASH” radiotherapy, which has an ultra-high dose rate. This technique was developed at Institut Curie by radiobiologist and researcher Vincent Favaudon and involves delivering a dose of radiation in a very short period of time. The usual dose is delivered into the tumor in less than 200 milliseconds, compared to several minutes with standard radiotherapy. Favaudon explains: “In our tumor models, a dose of 15 Gy administered conventionally to treat a lung tumor causes pulmonary fibrosis to appear, without fail, between eight weeks and six months after the irradiation, whereas with FLASH, no fibrosis appears below 20 Gy.” In other words, healthy tissue seems to better withstand this new method of irradiation, while the tumor has the same level of sensitivity to FLASH irradiation as to conventional treatment.

Radiotherapy : Fast, Powerful Treatment

This kind of performance requires extremely powerful devices capable of producing a radiation flow rate that is 1000 to 10,000 times more intense than that of conventional radiotherapy! Institut Curie’s Orsay site boasts a particle accelerator capable of just this, giving our researchers the opportunity to try out a range of different ideas: “We are interested in how FLASH radiotherapy might be used to treat certain brain cancers in children. It could be used to reduce side effects in patients with standard risk levels, enable us to increase the dose in patients with the most aggressive tumors, and—perhaps—treat the very youngest patients for whom the risk of side effects is currently too great,” explains Celio Pouponnot, a researcher at Institut Curie. The aim is also to carry out basic research to gain a clearer understanding of why healthy tissue has a higher tolerance level with this technique.

A Different Way of Targeting

Another approach, spatial this time, involves splitting the radiation into multiple tiny individual beams: this is known as “mini-beam” technology. Yolanda Prezado, who heads up the CNRS “New Approaches to Radiotherapy” team, has studied the value of this approach, in collaboration with Institut Curie: “Applied to proton therapy, this beam-splitting technique helps healthy tissue better withstand the treatment, while retaining comparable efficacy against the tumor. We have demonstrated this in preclinical models and now hope to carry out trials in humans.”

Improving Radiotherapy Through Medical Imaging

“To be able to be even more precise both spatially and in terms of the potential variation in target volumes, we need to get the best possible view of the tumor when the radiation is actually delivered,” explains Prof. Poortmans. One recent innovation in this field is MR-Linac, which couples highly precise magnetic resonance imaging with radiotherapy. “This could prove very useful for adapting the treatment in real time and in 3- or even 4-dimensions, particularly for tumors such as pancreatic cancer, which are very difficult to visualize precisely using other medical imaging techniques. Now that devices capable of doing this exist, we need to assess their actual clinical value,” he concludes.

copyright: Christophe Hargoues / Institut Curie