Arc Therapy Beats Tricky Cancer While Sparing Nearby Tissue
Context
A medical team at Corewell Health William Beaumont University Hospital, U.S., has successfully conducted the first-ever clinical use of Step-and-Shoot Spot-Scanning Proton Arc Therapy (SPArc) to treat adenoid cystic carcinoma in a patient.
The technique promises high precision in tumour targeting while sparing surrounding healthy tissues, particularly beneficial in complex regions like the skull base and for large tumours.
This comes at a time when conventional radiation therapy often results in severe side effects such as fatigue, nausea, and swallowing difficulties, significantly affecting patients’ quality of life.
Key Highlights of the Study
About SPArc Therapy
- Technique: Uses proton beams to deliver radiation with high precision.
- Step-and-Shoot Mode: Gantry moves in a 180º arc, stopping every 20º to deliver targeted doses.
- Dynamic SPArc: More advanced, adjusts energy and beam delivery in real-time. (Still under development)
Clinical Case
- Patient: 46-year-old woman with parotid-gland cancer that had spread to the skull base.
- Treatment: 33 sessions over three months.
- Outcome: Minor skin irritation, continued normal daily activities (eating, working).
- Monitoring: Cone-beam CT used to adjust doses in response to patient’s weight loss during therapy.
Advantages
- Radiation Exposure Reduction:
- Brainstem: ↓ 10%
- Optical Chiasm: ↓ 56%
- Oral Cavity: ↓ 72%
- Spinal Canal: ↓ 90%
- Tissue-Sparing Precision: Particularly useful for head, neck, and skull base cancers.
- Proton ‘Painting’: Proton beams delivered in energy layers to precisely target tumour volume.
Challenges
- Cost: Proton arc therapy is highly expensive, making it accessible to a limited patient base.
- Technological Barriers: Fully dynamic SPArc still awaits regulatory approval.
- Clinical Risk: Possibility of “geographical miss” due to tumour movement (e.g. breathing) or tumour shrinkage during treatment.
Conclusion
The first clinical application of step-and-shoot SPArc therapy represents a groundbreaking development in precision oncology. It has the potential to improve outcomes in complex and hard-to-reach cancers while drastically reducing harmful side effects compared to conventional radiation therapy.
However, high costs, limited accessibility, and technological refinement challenges remain significant hurdles before SPArc can become a widely adopted treatment option. Continued innovation, regulatory clearance, and cost reduction will be essential to integrate this life-saving technology into broader cancer care strategies globally.
