Carbon ion radiotherapy found effective in controlling growth of spinal sarcomas

Bruce G. Haffty, MD, FASTRO

The paper by Matsumoto and colleagues provides an interesting report of patients with unresectable spinal sarcomas treated with carbon ion radiation therapy. The report combines patients treated in a previously reported phase 1 dose escalation trial and subsequent phase 2 trial. The dose-distribution advantages of carbon ions — as with protons and other novel radiation therapy approaches — allows for higher doses to be delivered to the tumor, while minimizing the dose to the adjacent spinal cord. These data demonstrate promising long-term local control rates with acceptable toxicity. It is difficult, however, given the limitations of patient selection and other factors, to fairly compare the results with historical controls. Although the data appear promising and may be favorable, longer follow-up and further data are required to compare long-term outcomes and toxicities with other approaches. Ideally, randomized trials would be required to establish a high level of evidence that this approach is superior to other strategies, such as proton beam or intensity-modulated radiation therapy. Although randomized trials in this particular setting of a relatively rare disease are not likely in the near future, longer follow-up of patients in phase 2 trials such as this — using alternative approaches such as carbon ion, proton beam or other modalities evaluating dose escalation of radiation therapy — is needed. The current paper adds to the limited body of literature in this relatively rare disease.

Herrick J. Siegel, MD

Bone and soft tissue sarcomas involving the spine are often challenging to resect while achieving an acceptable margin and preserving the patient’s quality of life. New radiation treatment modalities that precisely target the tumor and minimize normal tissue injury include intensity-modulated radiation therapy (IMRT) and particle therapy (proton or carbon beams). Carbon ion radiotherapy (CIRT) has fewer negative effects on normal tissue while delivering a higher dose to a focal target than traditional external beam and IMRT.

The Working Group of Bone and Joint Sarcomas from Japan looked at the oncologic outcome and incidence of complications associated with the treatment of unresectable sarcomas involving either the cervical, thoracic or lumbar spine in 48 patients treated in a 15-year period. The majority (42 of 48) of the patients had osteosarcoma, chondrosarcoma, chordoma or malignant fibrous histiocytoma, most of which were located within 5 mm of the spinal cord. Researchers found that none of the 15 patients with tumors <100 cm³ developed a local recurrence and significantly fewer recurrences occurred in patients receiving >64 GyE . The 3- and 5- year local control rates were identical at 79% and 22 of 28 patients who were alive at the last follow up were ambulating without supportive devices

This study demonstrates that CIRT appears to be both effective and safe in this patient population, particularly in those patients with a tumor <100 cm³ and separated from the spinal cord by >5 mm. The use of this modality makes a significant contribution to our armamentarium in the treatment of spinal sarcomas.