[N-myc gene copies in children with neuroblastoma and its clinical significance].

This study was purposed to analyze the relation of N-myc gene copy number with clinical staging, pathological types and tumor biological factors in children with neuroblastoma (NB), and to investigate the influence of chemotherapy on N-myc gene expression and explore the relationship of N-myc gene copies with prognosis of NB children. The newly diagnosed children with NB from 1 March 2007 to 31 January 2011 were enrolled in this study. The treatment was carried out by BCH-NB-2007 based on Hongkong NB-07 protocol, and the patients were follow up to 31 January 2012. The N-myc gene in NB children was detected by FISH. According to number of N-myc gene copies, the NB children were divided into 3 groups. A group (N-myc gene negative) had less than 2 copies, B group (N-myc gene gains) had 3 to 9 copies, and C group (N-myc amplification) had more than 10 copies. The results showed that the N-myc gene expression in 58 cases of NB was observed. There were 36 males and 22 females. NB children aged from 6.5 to 138 months (median age 47.5 months), all patients were followed up for 11 - 57 months with an average of 31.5 months. INSS stages I-IV were 1, 5, 8 and 44 cases, respectively. Twenty-five cases had primary post mediastinal tumor, thirty-three cases had retroperitoneal and pelvic tumor, three of which also companied with post mediastinal tumor. Thirty-five cases had bone metastasis (60.3%), thirty-two cases had bone marrow metastasis (55%). Of the 54 patients with fully known biologic features, seventeen cases had ganglioneuroblastoma, thirty-seven cases had neuroblastoma (15 displayed differentiated, 7 poorly differentiated or undifferentiated, 15 with pathological changes after chemotherapy), four cases had bone marrow metastasis only detected by bone marrow biopsy. Eleven cases had N-myc gene negative, forty-three had N-myc gains, four had N-myc amplification. The average copy number of N-myc gene copies in 58 cases was 5.96 ± 7.81 in which 28 children were non chemotherapy cases, their average copy number was 4.00 ± 1.88, thirty cases out of 58 cases received preoperation chemotherapy (chemotherapy group), and their average copy number was 7.80 ± 10.46, the difference is significant (P = 0.064). The clinic stage, the location of primary tumor, pathological classification, urine VMA and serum neurogenic specific enolase had no effects on the N-myc gene expression, but the serum LDH level had influence (P < 0.01). Single factor Kaplan-Meier analysis showed that the number of N-myc gene copies in NB patients were closely related with the poor prognosis. The more copies of N-myc gene, the more poor prognosis, the difference is statistically significant (P < 0.05). It is concluded that the number of N-myc gene copies correlates with the rapid growth of NB and its poor prognosis, detecting the N-myc amplification can help to estimate the prognosis and decide the program of treatment. Serum LDH, which correlated with the rapid growth of NB, had effect on the N-myc gene expression and is closely related with the poor prognosis of NB.