LONG-TERM FOLLOW-UP OF EFFICACY AND SAFETY OF MEGAVOLTAGE RADIOTHERAPY IN HIGH-RISK GIANT-CELL TUMORS OF BONE

Purpose: Giant cell tumors of the bone are rare and have variable presentations and natural history. There may be significant functional sequelae as a result of their locally aggressive nature or as a result of treatment. We reviewed the long-term results of radiotherapy for high risk giant cell tumors to assess: the efficacy of radiotherapy and the potential late toxicity of treatment, and to determine indications for radiation treatment. Methods and Materials: This report is a retrospective review of 21 localized giant cell tumors of the bone treated with radiotherapy between 1959 and 1991. Radiation was used in the primary management of 13 cases and for recurrent disease in eight cases. In the primary cases, two received radiotherapy as the sole modality (including a massive pelvic lesion and an advanced maxillary sinus tumor with orbital and pterygoid invasion), and in the other 11, 3 had gross residual disease following surgery and 8 had microscopic residual disease. Of eight recurrent cases, five were treated with radiotherapy alone and three with combined surgery and radiation. Sites of origin included extremity bones in nine cases, pelvis in six, spine in four, and skull in two. Extraosseous disease was apparent in 18 tumors and extended to contiguous structures in 14 (including four cases of spinal cord compression, three cases of sacral plexopathy, and one patient with temporal lobe invasion). The most common dose regimen was 35 Gy/15 fractions/3 weeks (14 cases), with varying schedules for the remainder. Results: Mean follow-up time was 15.4 years (2 to 35 years). Local control was achieved in 19 of 21 patients with radiotherapy. The two failures were subsequently salvaged for an ultimate control rate of 100%. One of the two radiotherapy failures was a marginal failure and was subsequently salvaged with combined surgery and radiotherapy. No patient died of giant cell tumor. Radiotherapy was well tolerated, with no serious late toxicity. There were no cases of malignant transformation or radiation-induced cancer. Conclusion: Long-term results in this series indicate that radiotherapy in modest doses (35 Gy in 15 fractions or equivalent) is a safe and effective option for primary and recurrent giant cell tumors of the bone. Radiotherapy should be used if surgery would result in significant functional morbidity and should be considered in select sites where the probability of recurrence is high and there is potential for significant morbidity from tumor relapse or subsequent surgery.