Radiobiology at PTCOG64: Highlights & Horizons

Dear PTCOG community,

Attending PTCOG64 was, for me, a great reminder of why this meeting is so unique. While the scientific standards were remarkable, as always, its true value is the environment it creates for building meaningful relationships and initiating cross-border research initiatives.

What is clear to me, and I think to all of us, is that radiobiology is playing an increasingly central role in the field, underscoring the growing need for biologists, especially those skilled in new molecular biology technologies, omics and bioinformatics. And let’s not forget, radiobiology is not just essential, it is a winner, literally! Dr. Angelica Facoetti, radiobiologist from CNAO, Italy, took home the victory in the Balloon Debate!

The interplay between particle therapy and immunotherapy was one of the highlights. Protons and carbon ions showed a clear edge over photons when it comes to reprogramming the tumor microenvironment and boosting anti-PD-1 efficacy. Carbon ions looked particularly impressive in radioresistant models and in driving immunogenic cell death, while protons demonstrated encouraging systemic immune and normal tissue benefits, with molecular markers like telomere maintenance emerging as potential guides for patient selection down the line. Furthermore, the mechanistic insights into how particle therapy limits radiation-induced immunosuppression were especially relevant for clinicians, adding an important translational dimension to radiobiology. It is becoming indeed increasingly clear, that particle therapy protects the immune system through refined dose distribution, by preserving lymphocyte diversity, and sparing critical lymphoid structures.

It was also great to see new data on high-LET carbon-ion UHDR, with more labs independently showing that high-LET radiation can also induce a FLASH effect. This opens up an exciting prospect: eradicating even radioresistant tumors while still effectively sparing healthy tissue. The final biological outcome is shaped by a complex interplay of LET, tissue type, tumor subtype, the immune microenvironment, and beam structure. This clearly shows that while high-LET UHDR looks promising, its actual benefits, and mechanisms, need absolutely to be further clarified. Optimizing high-LET UHDR will require medical physicists, radiobiologists, and clinicians working much more closely together around different endpoints, which is exactly what PTCOG does by bringing together experts from all these different fields.

But the PTCOG64 was also the stage for an initiative that could reshape how radiobiologists and particle therapy centers work together going forward. Building on efforts already underway at the European Particle Therapy Network (EPTN), a proposal was put forward, during the radiobiology subcommittee, to create an interactive global map of radiobiology infrastructures across the PTCOG network. For this reason, we’re inviting international facilities to join in, to make resource-sharing and translational collaboration easier and help biologists quickly find the right facility for specific experiments. This will be added to the PTCOG website in the coming months, and we’ll share more details as they come. If you’d like to be part of this, feel free to reach out to me directly by email.

In conclusion, I would like to stress that for all of us biologists, regardless of our specific field, PTCOG remains an essential bridge between different disciplines, turning lab discoveries into real benefits for patients.

Looking forward to seeing you all at PTCOG65 in Bangkok!

Yours sincerely,

Walter Tinganelli

Co-Chairman of Scientific Program Subcommittee, Biology