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BACKGROUND The optimal administration of radiotherapy for patients with high-risk neuroblastoma (NB) currently is undefined in the context of modern therapy using myeloablative chemotherapy with autologous stem cell rescue (hematopoietic stem cell transplantation [HSCT]). METHODS The authors conducted a retrospective review of the records of 21 consecutive patients with high-risk NB to assess local control and toxicity of external beam radiotherapy (XRT). Therapy included multiagent induction chemotherapy and delayed surgical resection, consolidation of HSCT and local XRT, and 13-cis-retinoic acid maintenance therapy. XRT was delivered to the primary site, using postchemotherapy volumes, and to initial metastatic sites with 1–2 cm margins to 2100 centigrays (cGy) using 14 fractions administered once daily. RESULTS Four of 21 patients did not receive XRT due to toxic death (n = 2), disease progression before XRT (n = 1), or parental refusal (n = 1). The median time to XRT post-HSCT was 54 days. Thirteen patients received a second peripheral blood stem cell infusion after completing XRT. Twelve of the 14 patients who received XRT post-HSCT and for whom toxicity data were available had Grade 3–4 acute toxicities, including gastrointestinal toxicity (n = 8), hematologic toxicity (n = 9), and infection (n = 1). Nonrecurrent long-term toxicities included prolonged nutritional deficiency (n = 9) and leg-length discrepancy (n = 1). Tumors recurred in 7 of 21 patients (5 of 17 patients who received radiotherapy), either within a radiation field (n = 1) or at distant nonirradiated sites (n = 6). The estimated local failure rate was 7% (95% confidence interval [95% CI], 0–14%), with a 2-year event-free survival rate of 48% (95% CI, 26–70%). CONCLUSIONS Post-HSCT, fractionated XRT to 2100 cGy was a tolerable and effective treatment for patients with high-risk NB, and minimal recurrences were observed at designated XRT sites. Cancer 2004. © 2004 American Cancer Society.