High-dose rate intraoperative radiation therapy for pediatric solid tumors

Sixteen pediatric patients with solid tumors received treatment on a protocol designed to test the feasibility and safety of high-dose rate intraoperative radiation therapy (IOHDR) via a remote afterloader.

Patients with Ewing's sarcoma (n = 5), rhabdomyosarcoma (n = 3), synovial cell sarcoma (n = 2), Wilms tumor (n = 2), osteosarcoma, immature teratoma, desmoplastic small round cell tumor, and inflammatory fibrosclerosis were included. IOHDR was used in the initial management of nine patients and at the time of recurrence in seven. Indications for treatment included gross residual disease in 5 and suspected microscopic disease in 11. The general sites treated were the abdomen (n = 3), chest-wall/thoracic cavity (n = 7), and pelvis (n = 6). All of the patients received multiagent chemotherapy prior to the IOHDR procedure, and 5 had been previously treated with external beam radiation therapy. Separate from the procedure during which IORT was performed, 9 patients underwent an attempt at resection at the time of their initial presentation. A dose of 1200 cGy was prescribed to a depth of 0.5 cm from the surface of a multichannel tissue-equivalent applicator. Complications ascribed to IOHDR included an abscess, delayed wound healing, and cytopenia. Four patients received supplemental external beam radiation therapy to the IOHDR site. At the time of IOHDR, 3 patients had disseminated disease within the pleural cavity and one had pulmonary metastases.

With a median follow-up of 18 months, the actuarial rates of local control, metastasis-free, and overall survival at 2 years were 61%, 51%, and 54%, respectively. The patterns of failure were local (n = 1), distant (n = 1), and local + distant (n = 1). Two patients are alive with active disease. Nine are alive with no evidence of disease and the remaining 5 are dead from disease (n = 2), other causes (n = 1), or treatment (n = 2).

The potential to improve local control with high doses of radiation should be balanced against the risk of late effects. The ability to confine the dose of radiation to the primary site and decrease the dose to normal tissues makes IOHDR an important adjunct to external beam radiation therapy. IOHDR can be a safe and integral component in the management of pediatric solid tumors.