Osteochondroma in long-term survivors of high-risk neuroblastoma

BACKGROUND Osteochondromas are benign bony protrusions that can be spontaneous or associated with radiotherapy (RT). Current treatment of high-risk neuroblastoma includes dose-intensive chemotherapy, local RT, an anti-G_D2 monoclonal antibody (MoAb), and isotretinoin. Late effects are emerging. METHODS The authors examined osteochondromas in 362 patients who were aged <10 years when diagnosed with neuroblastoma, had received a MoAb plus isotretinoin since 2000, and had survived >24 months from the time of the first dose of the MoAb. The incidence rate of osteochondroma was determined using the competing risks approach, in which the primary event was osteochondroma calculated from the date of neuroblastoma diagnosis and the competing event was death without osteochondroma. RESULTS A total of 21 osteochondroma cases were found among 14 patients who were aged 5.7 to 15.3 years (median, 10.4 years) and 3.1 to 11.2 years (median, 8.2 years) from the time of neuroblastoma diagnosis. The cumulative incidence rate was 0.6% at 5 years and 4.9% at 10 years from the neuroblastoma diagnosis. Nine osteochondromas were revealed incidentally during assessments of neuroblastoma disease status or bone age. Thirteen osteochondromas were detected outside RT portals and had characteristics of spontaneous forms. Complications were limited to pain necessitating surgical resection in 3 patients, but follow-up was short at 0.3 to 7.7 years (median, 3.5 years). CONCLUSIONS Osteochondromas in long-term survivors of neuroblastoma should be expected because these benign growths can be related to RT and these patients undergo radiologic studies over years, are monitored for late toxicities through and beyond adolescence, and receive special attention (because of concerns about disease recurrence) if they develop a bony protuberance. A pathogenic role for chemotherapy, anti-G_D2 MoAbs, or isotretinoin remains speculative. Cancer 2015.