Proton therapy in pediatric skull base and cervical canal low-grade bone malignancies

To evaluate outcomes and tolerance of high-dose photon and proton therapy in the management of skull base and cervical canal primary bony malignancies in children.

Thirty children were treated postoperatively with high-dose photon-proton (29 patients) or protons-only (1 patient) radiotherapy. Twenty-six patients had chordomas (CH), 3 had low-grade chondrosarcomas (CS), and 1 had an aggressive chondroma (AC). The mean age was 12.8 years. At the time of radiation, all but 1 patient had a gross residue. The anatomic sites affected were skull base (n = 16), cervical canal (n = 1), or both (n = 13). Mean total dose was 68.4 cobalt Gray equivalents, conventionally fractionated.

With a mean follow-up of 26.5 months, 5 of 30 children failed locally: 5 of 5 lesions were CH, 5 of 5 patients had experienced pain at presentation (p = 0.03), and 4 of 5 had cervical extension (p = 0.07). The 5-year overall survival/progression-free survival rates for CS and CH were 100%/100% and 81%/77%, respectively. Side effects were scored according to the National Cancer Institute Common Terminology Criteria for Adverse Events v3.0. Acute toxicity ranged between 0 and 2. Late toxicity of radiotherapy was severe in 1 patient (Grade 3 auditory) and minor or mild in the rest of the population (7 patients with Grade 2 pituitary dysfunction).

High-dose combined fractionated photon-proton therapy is well tolerated in children and allows excellent local control with minimal long-term toxicity.