Radiotherapy for local control of osteosarcoma.

PURPOSE: Local control of osteosarcoma in patients for whom a resection with satisfactory margins is not achieved can be difficult. This study evaluated the efficacy of radiotherapy (RT) in this setting. METHODS AND MATERIALS: We identified 41 patients in our sarcoma database with osteosarcomas that either were not resected or were excised with close or positive margins and who underwent RT with external beam photons and/or protons at our institution between 1980 and 2002. Patient charts were reviewed to assess local control, progression-free survival, metastasis-free survival, and overall survival.
RESULTS: The anatomic sites treated were head/face/skull in 17, extremity in 8, spine in 8, pelvis in 7, and trunk in 1. Of the 41 patients, 27 (65.85%) had undergone gross total tumor resection, 9 (21.95%) subtotal resection, and 5 (12.2%) biopsy only. The radiation dose ranged from 10 to 80 Gy (median 66). Twenty-three patients (56.1%) received a portion of their RT with protons. Chemotherapy was given to 35 patients (85.4%). Of the 41 patients, 27 (65.85%) were treated for localized disease at primary presentation, 10 (24.4%) for local recurrence, and 4 (9.8%) for metastatic disease. The overall local control rate at 5 years was 68% +/- 8.3%. The local control rate according to the extent of resection was 78.4% +/- 8.6% for gross total resection 77.8% +/- 13.9% for subtotal resection, and 40% +/- 21.9% for biopsy only (p < 0.01). The overall survival rate according to the extent of resection was 74.45% +/- 9.1% for gross total resection, 74.1% +/- 16.1% for subtotal resection, and 25% +/- 21.65% for biopsy only (p < 0.001). Patients with either gross or subtotal resection had a greater rate of local control, survival, and disease-free survival compared with those who underwent biopsy only at 5 years (77.7% +/- 7.5% vs. 40% +/- 21% [p <0.001], 73.9% +/- 8.1% vs. 25% +/- 21.6% [p <0.001], and 51.9% +/- 9.1% vs. 25% +/- 21.6% [p <0.01], respectively). Overall survival was better in patients treated at primary presentation (78.8% +/- 8.6% compared with 54% +/- 17.3% for recurrence) p <0.05). No definitive dose-response relationship for local control of tumor was seen, although the local control rate was 71% +/- 9% for 32 patients receiving doses > or =55 Gy vs. 53.6% +/- 20.1% for 9 patients receiving <55 Gy (p = 0.11). Of 15 patients with tumors >5.3 cm, 9 received doses > or =55 Gy and the local control rate was 80% +/- 17.9%, and 6 received doses <55 Gy with a local control rate of only 50% +/- 25% at 5 years (p = 0.16). Among patients who underwent gross total resection, the local control rate was 77.5% +/- 9.95% in 22 patients with negative margins vs 66.7% +/- 27.2% in 3 patients with positive margins (p = 0.54). Two patients had unknown margin status.
CONCLUSION: RT can help provide local control of osteosarcoma for patients in whom surgical resection with widely, negative margins is not possible. It appears to be more effective in situations in which microscopic or minimal residual disease is being treated.