Abstract
Statement of purpose
We review the current state of development of proton therapy and the implications for beam therapy in the management of primary bone tumours
Introduction
The principle of radiotherapy is to deliver a high dose, accurately, to the tumour. Conventional photon and proton therapy irradiates adjacent tissue significantly. This is reduced with intensity modulated proton therapy (IMPT). This has been demonstrably effective in treating tumours refractory to chemotherapy and conventional radiotherapy such as chrondrosarcomas and chordomas
Case Report
We present a patient with an isolated chondrosarcoma involving the anterior and posterior element of the L3 vertebral body with a significant soft tissue component displacing the IVC. The patient underwent a 2 stage en-bloc excision of the tumour: Stabilization was achieved by posterior L2-4 instrumented fusion with PEEK rods, an anterior PEEK cage and bone graft. Post-operatively the patient underwent 12 weeks of bed rest followed by rehabilitation. Due to pedicle involvement (giving a high risk of contamination) and the narrow clear margin found on histology the patient has been accepted for post-operative IMPT.
Discussion
The high risk of contamination and the narrow margins presented an ideal case for post-operative IMPT. However, conventionally the stabilization would have been metallic, distorting the treatment mapping and the delivery of the IMPT, reducing any possible benefit. Thus, we used PEEK as it is proven to maintain its properties when subjected to a wide range of conditions while also being tolerant of, and not interfering with, most forms of radiation including proton therapy, maximising the chance of a positive outcome. One concern is that PEEK is less biomechanically stable then metal, hence the prolonged period of bed rest.
Conclusion
This report discusses the current evidence for proton therapy while describing a successful technique for stabilization to facilitate delivery of proton treatment post-operatively.
