Reimagining Radiotherapy: Can Upright Positioning Improve Carbon Ion Treatments?

Radiotherapy is constantly evolving, driven by the dual goals of improving treatment precision and expanding patient access to advanced technologies.

Upright patient positioning has seen a resurgence in recent years, which challenges the long-standing convention of treating patients in either a supine or prone position. With growing data indicating that it may offer opportunities for greater precision, increased accessibility and the potential for a better patient and clinician experience.

The renewed interest in upright patient positioning is particularly relevant for carbon ion radiotherapy (CIRT). CIRT offers clear dosimetric and biological advantages for selected tumors, with its heavy mass and ability to deposit high energy right at the tumor and not the surrounding tissue. Carbon ions have shown to be the most effective at treating hypoxic radioresistant tumors, however its widespread adoption is limited by the complexity and cost of treatment delivery systems.

Globally, most facilities currently use a fixed carbon ion beam, with treatments typically delivered while the patient lies down, limiting treatment angles and patient positioning. Rotating carbon ion gantries can weigh in excess of 600 tonnes, requiring substantial space and financial investment, for this reason there are limited numbers in use globally.

Upright positioning, combined with patient rotation, presents an intriguing alternative that utilizes smaller fixed beam treatment delivery systems but offers 360 degrees of beam angle along with reduced infrastructure complexity and lower costs.

A recent study carried out at Gunma University Heavy Ion Medical Center led by Varnava et al (2025), investigated whether upright patient positioning could be applied in CIRT for abdominal and head and neck treatments by evaluating interfractional and intrafractional motion.

This study included 10 healthy volunteers positioned using a demo upright positioning system provided by Leo Cancer Care, along with an optical guidance and tracking system. Three different setups were evaluated for two different anatomical sites; abdomen and head and neck. The three setups included: No immobilization devices (“none”), vacuum bags only (“vacuum”), and vacuum bags with thermoplastic shell (“shell”).

Each setup was repeated five times to assess reproducibility, with a focus on interfractional and intrafractional motion.  

Results showed significant differences in interfractional motion between the three different immobilization configurations in both anatomical regions. The abdominal area showed that increased immobilization, including a vacuum bag and thermoplastic shell, both moulded to the individual volunteer, led to consistently improved positional reproducibility.  

For the head and neck region, there was a significant reduction in lateral motion between the “none” and “vacuum” setups, and a significant reduction in superior–inferior motion between the “vacuum” and “shell” setups. 

The “shell” setup showed the lowest intrafractional motion for both anatomical sites. The absolute differences between setups were in the order of a few millimeters, but such magnitudes remain clinically relevant considering the steep dose gradients and high positional accuracy requirements associated with CIRT.  

This study demonstrates that upright patient positioning in carbon ion radiotherapy is both feasible and promising, provided that appropriate immobilization and image guidance strategies are used.  

The findings underline the critical role of immobilization design in upright radiotherapy. In anatomical regions such as the abdomen, which are more sensitive to gravitational and postural effects, more comprehensive immobilization was associated with greater reductions in motion. For head and neck treatments, simpler immobilization provides some reduction in motion. The authors of this research suggested that suboptimal construction and fixation of the head and neck vacuum bags and thermoplastic shells might have affected the results seen.  

Further optimization of immobilization techniques is necessary to fully realize the clinical potential of upright positioning in CIRT. 

From a clinical perspective, upright positioning could enable greater beam angle flexibility in fixed-beam CIRT facilities, potentially reducing reliance on large and costly rotating gantries, taking this treatment to more people that need it in the future.   

Further research will focus on refining upright immobilization techniques, integrating these workflows into clinical image guidance systems, and validating the approach in patient cohorts. With continued technical development and clinical evaluation, upright carbon ion radiotherapy has the potential to evolve from a feasibility concept into a practical and clinically viable treatment option in the future. 

Reference

Varnava, M., et al. Assessment of upright immboilization methods for abdominal and head-and-neck cancer treatments in a carbon ion radiotherapy setting. Technical Innovations and Patients Support in Radiation Oncology. 2025. 36. https://doi.org/10.1016/j.tipsro.2025.100356.