New advances in carbon ion therapy for challenging large tumours

A pioneering study has introduced a novel approach to enhance the treatment of large sacral chordomas using carbon ion therapy. The study focuses on optimizing dose-averaged linear energy transfer (LETd), a critical parameter in radiotherapy that directly influences treatment efficacy for challenging tumours. The findings, published in Medical Physics, could significantly impact clinical outcomes for patients with these aggressive and resistant cancers. 

Carbon ion therapy is a highly precise cancer treatment that exploits the unique physical and biological properties of carbon ions. While traditionally successful in treating smaller tumours, its efficacy diminishes with larger targets due to lower LETd distribution, reducing treatment potency. A recent study by MedAustron Ion Therapy Center and Karl Landsteiner University of Health Sciences (KL Krems) addressed this gap by leveraging advanced treatment planning system (TPS) functionalities.

Breakthrough findings

“Our research demonstrates that by optimizing LETd distributions, we can significantly enhance the biological effectiveness of carbon ion therapy in large tumours, such as sacral chordomas, without compromising safety or precision,” says Prof. Markus Stock, senior author of the study, head of the Division of Medical Physics with an emphasis on Particle Therapy at KL Krems and Head of Medical Physics at MedAustron.

In detail the study compared conventional and LETd-optimized treatment plans for large tumours exceeding 250 cm³. It revealed that LETd optimization achieved:

• Up to 34 % higher LETd in tumours: Increasing the concentration of high-energy ion interactions where they are most needed.
• Preservation of safety for surrounding tissues: Critical organs like the bowel, nerves, and spinal cord were spared effectively.
• Minimal impact on treatment time: Optimization added negligible delay to the planning and delivery process.

By employing cutting-edge LETd optimization techniques integrated into the RayStation TPS, an advanced TPS for radiation therapy, the team in collaboration with Prof. Piero Fossati (Director of the Carbon Ion Therapy Program at MedAustron and Prof. on Radiation Oncology at KL Krems) ensured robust dose coverage while tailoring high-LET zones to resistant tumour regions.

Implications for clinical practice

This advancement provides a potential lifeline for patients with large, previously difficult-to-treat tumours. “Large chordomas are often associated with inferior clinical outcomes due to their size and proximity to sensitive organs,” notes Dr. Mansure Schafasand, first author of the study and colleague of Prof. Stock. “Our optimized planning strategy is an important step towards improving survival rates and quality of life for these patients.”

This study underscores the importance of LETd as a predictive factor for treatment success. It also aligns with recent research in so-called “LET painting” strategies. Here LET levels are deliberately modulated within the tumour to target resistant tumour regions. The findings of the study by the team of researchers at KL Krems and MedAustron pave the way for broader applications in carbon ion therapy and may inspire further research into adaptive and personalized radiotherapy techniques. It also highlights the importance the KL Krems gives to relevant clinical research that contributes to patients’ quality of life.

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