Brachytherapy in the combined modality treatment of pediatric malignancies. Principles and preliminary experience with treatment of soft tissue sarcoma (recurrence) and Ewing's sarcoma.

Radiotherapy is an integral part in the treatment of soft tissue and Ewing's sarcoma in children. By brachytherapy a high dose can be delivered in a restricted volume with sparing of normal tissues surrounding the target. Taking into account this principle potential benefit brachytherapy may play some role in the local treatment especially in children. However, only limited experience with pediatric brachytherapy has been reported apart from a few centers, which have gained their experience with Low-Dose-Rate (LDR)-brachytherapy. Since 1991 - 12 patients with soft tissue sarcoma and 6 patients with Ewing's sarcoma were treated with High-Dose-Rate (HDR) and Pulse-Dose-Rate (PDR)-brachytherapy at the departments of radiotherapy in Münster, Kiel and Vienna. The combined modality treatment was performed according to the CWS-86/91, EICESS-92 and CESS/CWS-REZ-91 protocols. In 8 patients with soft tissue sarcoma brachytherapy was part of the recurrence treatment regime, in 4 patients brachytherapy was part of the primary treatment alone or in combination with external beam therapy. In HDR-treatment a dose of 15 to 43 Gy was delivered in 3 to 16 fractions, in PDR-treatment 13 to 36 Gy in fractions of 1 Gy/hour. Follow-up is 3-39 months (median 14 months). 7 patients show no evidence of disease, 9 patients are locally controlled and 3 patients progressed locoregionally. In 6 patients with Ewing's sarcoma brachytherapy was performed intraoperatively as a boost treatment after external beam therapy (50-55 Gy), if no wide resection could be achieved within first line-treatment. A dose of 10-12 Gy was applied in one fraction in a limited volume (20-50 ccm) at the time of surgery. Follow-up is 13-26 months (median 21 months). There is no evidence of disease in all patients, perioperative and subacute morbidity was not increased. These encouraging preliminary results with HDR/PDR-brachytherapy must be further evaluated prospectively and systematically within an interdisciplinary approach by some specialized collaborating centers, which not only have the equipment (HDR/PDR/(LDR)-brachytherapy) but also can meet the complex demands to accumulate the necessary experience.