Carbon Ion Radiotherapy Works for Spinal Sarcoma

Carbon ion radiotherapy is a safe and effective method for treating unresectable spinal sarcomas, according to a retrospective analysis from one center in Japan.

Spinal sarcomas account for no more than 13% of all orthopedic tumors, and the standard treatment has been en bloc resection. These are challenging procedures, however, and piecemeal resection can lead to a high rate of local recurrence. Radiotherapy of various types has also been considered for those patients, but doses are usually kept low, again limiting the amount of local control that is possible. Carbon ions, however, are heavier than protons and carry a greater probability of tumor control.

“Although most sarcomas are considered radioresistant and difficult to control with conventional radiotherapy, these advantageous treatment profiles with carbon ion beams contribute toward achieving a lower irradiated dose to the spinal cord and an improved local control rate for spinal sarcomas,” wrote authors led by Keiji Matsumoto, MD, of the National Institute of Radiological Sciences in Chiba, Japan. An analysis of 47 patients who underwent carbon ion radiotherapy (CIRT) between 1996 and 2011 was published online ahead of print on August 12 in Cancer.

All patients were enrolled in phase I/II and phase II clinical trials of CIRT. The median dose received was 64 Gy equivalents, given in 16 fixed fractions over 4 weeks. Most of the patients (35) had not had any prior treatment, while the remaining 12 had a previous resection followed by a local recurrence. Patients were followed for a median of 25 months.

The median survival was 44 months, ranging from 5.2 months to 148 months. The 3-year and 5-year local control rates were both 79%; eight patients had local failure, three of which occurred inside the irradiated field. The other five experienced marginal recurrences at the boundary between the spinal cord and the tumor.

Local control was better in patients with smaller tumors: the control rate was 100% in those patients with tumors less than 100 cm³, compared with 67% in those with tumors above that size (P = .0194). Also, patients who received doses below 64 Gy equivalents developed more local recurrences than those who received higher doses (P = .0252). Three-year and 5-year overall survival rates were 59% and 52%, respectively, and progression-free survival rates were 48% and 44%, respectively.

CIRT was relatively well tolerated; there were no fatal toxicities during follow-up. There was one grade 3 irradiated skin reaction in the acute phase, and one patient had a late grade 3 skin reaction. One other patients developed a late grade 4 skin reaction and eventually required skin grafts. Seven patients experienced vertebral body compression inside the irradiated field.

“Although longer follow-up is still needed… CIRT appears to be both effective and safe as a treatment for patients who have unresectable spinal sarcoma,” the authors wrote. “In particular it will be useful for small tumors and tumors separated from the spinal cord.”