High-dose chemoradiotherapy supported by marrow infusions for advanced neuroblastoma: a Pediatric Oncology Group study [published erratum appears in J Clin Oncol 1991 Jun;9(6):1094] We conducted a pilot protocol at seven Pediatric Oncology Group (POG) institutions to examine the feasibility, toxicity, and efficacy of using a common regimen of high-dose chemoradiotherapy (HD CT/RT) supported by autologous or allogeneic marrow infusions in children with metastatic neuroblastoma (NBL) in first or second remission. During a 57-month period, we accrued 101 patients. We report here results for the 81 who completed treatment at least 2 years ago. The HD CT/RT regimen consisted of melphalan 60 mg/m2/d for three doses, and total body irradiation (TBI) either 1.5 Gy (n = 27) or 2.0 Gy (n = 54) twice daily for six doses. Twenty-three patients also received irradiation consisting of 1.2 Gy twice daily for 10 doses to persisting disease sites. Seventy-four were given autologous and seven allogeneic marrow, 64 autologous marrows being purged immunomagnetically. Fifty-four children were in first complete (CR) or partial (PR) remission and 27 in second CR or PR. As of October 1, 1990, follow-up was from 32 to 72 months. Forty-seven of these 81 children relapsed, 10 died of complications, one of unknown cause, and 23 continue in remission, including 21 of the 54 treated in first remission, and 16 who completed treatment more than 3 years ago. The 2-year actuarial event-free survival (EFS) probabilities are first CR (CR1) 32% (SE 10%), first PR (PR1) 43% (SE 9%), second CR (CR2) 33% (SE 27%), and second PR (PR2) 5% (SE 5%). Probability of EFS correlated with remission number (first better than second, P less than .001), with interval from diagnosis to HD CT/RT (greater than 9 months better than less than 9 months, P = .055), and with TBI dose (12 Gy better than 9 Gy, P = .031). These encouraging results may partly reflect selection for this treatment of patients with NBL who have a slower disease pace. 