Has « complication-free » radiotherapy emerged?

by Marie-Catherine Vozenin,

Head of the CHUV Radiation Oncology Laboratory | Vaud University Hospital Center

Associate Professor at the Radio-Oncology Department,

Vaud University Hospital Center and University of Lausanne

President of ARSER Switzerland

Radiotherapy has been used for more than a century to treat cancer, alone or in combination with surgery or chemotherapy. With advances in technology, radiotherapy has evolved steadily to become one of the most successful and cost-effective tools in the fight against cancer today, with half of cancer patients treated at some point in treatment.

Over the past two decades, technological advances (more targeted, computer-guided treatment) have transformed radiotherapy into a precise and personalized treatment. Nevertheless, the treatment of more resistant tumours, which may require a higher dose of radiotherapy to obtain tumor control, remains limited by the risk of complications in healthy tissues due to the risk of sequelae in long-survivors of cancer and/or or by the progression of the cancer by development of a local recurrence or the occurrence of metastases.

Therefore, the pursuit of the improvement of radiotherapy by a selective radio-sensitization of the tumor remains the current challenge of the community of researchers and physicians in radiation oncology. The last decades have made progress thanks to the improvement of machines (going from Cobalt to the linear accelerator) or the use of radio-sensitizing chemotherapy such as cisplatin or immunotherapy.

In this context for fifteen years, my team has conceptualized and implemented a new approach in radiotherapy based on the use of ultra-high dose rate (UHDR) irradiation which makes it possible to deliver the irradiation dose in a fraction of a second, whereas standard radiotherapy requires several minutes. We have called this new method FLASH radiotherapy (FLASH-RT). In addition to being very fast, FLASH-RT has overturned our knowledge by allowing tumor cells to be killed without complication in healthy tissues.

To be able to offer this treatment in humans, technical challenges (to achieve high throughput) must still be met. For this we collaborate with the best of world physics: accelerator physicists from CERN in Europe, PSI in Switzerland and SLAC in the USA. We are progressing in parallel towards “clinical” trials by treating pets (cats and dogs) sick with cancer in collaboration with veterinarians. Today, many teams around the world have followed this new approach and our scientific community has been able to show the interest of FLASH-RT in several preclinical models (in fundamental research). Finally, we are working enthusiastically in my laboratory to understand the mechanisms (“how it works”) so that FLASH-RT can in the near future be offered to cancer patients under the best conditions of safety and effectiveness.