Carbon ion radiotherapy for inoperable pediatric osteosarcoma.

Background: Unresectable pediatric osteosarcoma has poor outcomes with conventional treatments.

Results: Twenty-six patients aged 11-20 years (median 16) had inoperable osteosarcoma of the trunk (24 pelvic, 1 mediastinal and 1 paravertebral) without any other lesion at initial examination. There were 22 primary, 1 locally recurrent and 3 metastatic cases. Median CIRT dose was 70.4 Gy RBE (relative biological effectiveness) delivered in 16 fractions. Median follow-up was 32.7 months. Overall survival was 50.0% and 41.7% at 3 and 5 years, respectively. Ten patients survived for more than 5 years (range 5-20.7 years). Local control was 69.9% and 62.9% at 3 and 5 years, respectively and progression-free survival was 34.6% at 3 and 5 years. Only largest tumor diameter correlated with 5-year overall survival and local control. There were 4 grade 3-4 CIRT-related late toxicities, 1 case of bone fracture and no treatment-related mortalities. All patients (except 1) were able to ambulate after CIRT.

Conclusions: CIRT was safe and efficacious in the treatment of inoperable pediatric osteosarcoma with improved local control and overall survival compared to conventional treatments.

Methods: We retrospectively reviewed the records of pediatric and adolescent patients who received carbon ion radiotherapy (CIRT) for inoperable osteosarcoma between 1996 and 2014.