Proton radiation therapy for chordomas and chondrosarcomas of the skull base

Local tumor control, patient survival, and treatment failure outcomes were analyzed to assess treatment efficacy in 58 patients in whom fractionated proton radiation therapy (RT) was administered for skull base chordomas and chondrosarcomas.

Between March 1992 and January 1998, a total of 58 patients who could be evaluated were treated for skull base tumors, 33 for chordoma and 25 for chondrosarcoma. Following various surgical procedures, residual tumor was detected in 91% of patients; 59% demonstrated brainstem involvement. Target dosages ranged from 64.8 and 79.2 (mean 70.7) Co Gy equivalent. The range of follow up was 7 to 75 months (mean 33 months). In 10 patients (17%) the treatment failed locally, resulting in local control rates of 92% (23 of 25 patients) for chondrosarcomas and 76% (25 of 33 patients) for chordomas. Tumor volume and brainstem involvement influenced control rates. All tumors with volumes of 25 ml or less remained locally controlled, compared with 56% of tumors larger than 25 ml (p = 0.02); 94% of patients without brainstem involvement did not experience recurrence; in patients with brainstem involvement (and dose reduction because of brainstem tolerance constraints) the authors achieved a tumor control rate of 53% (p = 0.04). Three patients died of their disease, and one died of intercurrent disease. Actuarial 5-year survival rates were 100% for patients with chondrosarcoma and 79% for patients with chordoma. Grade 3 and 4 late toxicities were observed in four patients (7%) and were symptomatic in three (5%).

High-dose proton RT offers excellent chances of lasting tumor control and survival, with acceptable risks. In this series all small- and medium-sized tumors with no demonstrable brainstem involvement have been controlled; all such patients are alive. Surgical debulking enhanced delivery of full tumoricidal doses, but even patients with large tumors and disease abutting crucial normal structures benefited.