Enabling gantry-less radiotherapy through upright patient positioning: Current consensus and future direction.

PURPOSE: Gantry-less radiotherapy with a fixed treatment beam, in which an upright patient is slowly rotated, promises reductions in treatment room costs and could offer anatomical / comfort benefits for certain patients. Several radiotherapy centres worldwide have now designed or acquired upright patient immobilization systems; however, many aspects of the upright treatment workflow are yet to be fully addressed. MATERIALS & METHODS: During the 2024 ESTRO physics workshop on "Gantry-less Radiotherapy: Challenges and Opportunities", 22 participants, including medical physicists, a radiation oncologist, academics and representatives from industry, discussed in-depth the open questions and existing solutions for clinical implementation. Clinical aspects, technical and implementation challenges, opportunities and a "wish-list for vendors" were addressed. RESULTS: Imaging and immobilisation present crucial challenges, but ongoing research projects and industrial development are progressing in both areas. However, the lack of upright patient data, data sharing issues, and the limitations associated with data generation have been recognized as significant obstacles to achieving clinically meaningful evaluations. A priority-ranked wish-list for vendors, covering immediate clinical needs and future opportunities is presented as one result of the experts' discussion. CONCLUSION: Gantry-less radiotherapy with upright patient positioning holds significant promise for simplifying treatment delivery, improving accessibility, reducing costs and providing a streamlined platform for innovative new technologies. However, many challenges remain. The most critical part is clinical and technical evidence. Realizing the potential of gantry-less treatments will require continued collaborative efforts from academia, hospitals, and industry, ideally supported by national and international societies.