Feasibility of intraoperative high-dose rate brachytherapy to boost low dose external beam radiation therapy to treat pediatric soft tissue sarcomas.

Abstract

To determine if a single intraoperative high-dose-rate brachytherapy (IOHDR) dose can be used in conjunction with low dose external beam radiation therapy (EBRT) to treat soft tissue malignancies in children with reduced morbidity. From March 1992 to February 1995, six pediatric patients (4 boys, 2 girls; ages ranging from 4-13 years; median 10.5 years) were treated with IOHDR in conjunction with EBRT, chemotherapy, and radical surgery at nine sites not treatable by standard intraoperative electron beam radiation therapy techniques. The IOHDR dose was 10 Gy (at 7 sites with microscopic residual disease) or 12.5 Gy (at 2 sites with minimal gross residual disease) prescribed at 0.5 cm depth. The treatment volume varied from 9-96 cc (mean 30.3 cc). IOHDR was used in these patients because the tumor locations prevented positioning and insertion of conventional intraoperative electron beam applicators. The EBRT dose was limited to 27-30.6 Gy (median dose 27.4 Gy) postoperatively in all patients to minimize growth retardation or altered organ function. The median initial EBRT field size was 211 cm2 (range 25-483), with a median of two fields per patient (range 1-2). After a median follow-up of 40 months (range 22-62 months), all the patients were alive, five of them without evidence of disease. The other patient, with stage IV undifferentiated synovial sarcoma developed regrowth of pulmonary metastases at 14 months and local failure at 34 months. Toxicity was seen in two patients. One patient developed recurrent urinary infections and ureteral stenosis after 6 months and required a left nephrectomy. Another developed mild to moderate loss of visual acuity and impaired orbital growth after 6 months. Use of IOHDR in conjunction with low dose EBRT to obtain local control and long-term disease-free survival in pediatric soft tissue sarcomas is feasible with acceptable toxicity. Tumor beds not treatable with standard electron beam intraoperative radiation therapy could be satisfactorily encompassed with IOHDR.