Intensity-modulated radiation therapy with dose-painting for pediatric sarcomas with pulmonary metastases

We examined patterns of failure in pediatric patients with thoracic sarcoma and pulmonary metastases treated with intensity-modulated radiation therapy with dose-painting (DP-IMRT).

Eleven pediatric patients, five with Ewing sarcoma family tumors (ESFT) and six with rhabdomyosarcoma (RMS), with primary thoracic tumors and pulmonary metastases underwent DP-IMRT with chemotherapy for definitive treatment. Eight patients also underwent surgery. Median time to RT was 21 (15-31) weeks. Nine patients received 45-50.4-Gy in 1.8 Gy fractions to the primary tumor (n = 3) or post-operative tumor bed (n = 6). Two patients ≤4 years received 12 Gy intraoperative radiation therapy and 30.6-36 Gy IMRT postoperatively to the tumor bed. All patients received 14-16.8 Gy in 0.54-0.88 Gy fractions to the whole lungs (n = 6) or hemithorax (n = 5) using dose-painting technique. A representative case was re-planned with IMRT plus standard AP/PA whole lung irradiation (WLI) for dosimetric comparison.

With 27-month median follow-up, 3-year pulmonary relapse-free survival in all patients was 61%: 80% for RMS and 40% for ESFT. Five patients (4 ESFT and 1 RMS) experienced pulmonary relapse at median 16 (9-41) months. There were no local failures. Our representative case demonstrated more homogeneous target volume coverage of the whole lungs and decreased mean dose to esophagus (15%), heart (31%), spinal cord (15%), and liver (19%) with DP-IMRT.

The treatment of children with a primary thoracic tumor and pulmonary metastases poses a significant challenge. DP-IMRT is one solution to this technical problem. Initial data from this small series suggest DP-IMRT is feasible and produces superior sparing of critical normal tissues.