Insights into infant neuroblastomas based on an analysis of neuroblastomas detected by mass screening at 6 months of age in Japan.

BACKGROUND/PURPOSE: Mass screening (MS) for neuroblastoma (NB) at 6 months of age in Japan was discontinued in 2004. We have previously reported that the majority of NB detected by MS showed a good prognosis, with only a few cases demonstrating an unfavorable outcome (J Pediatr Surg 2002, Cancer 2001). This study aims to provide insights into infant NB by assessing the details of the clinical courses in patients treated with a standard regimen and the biological features of such cases using highly sensitive methods at one institution in Japan.

METHODS

In 76 NB detected through MS treated at Kyushu University Hospital, the clinical features and MYCN amplification, 1p deletion, 17q gain, the expression level of TRKA using FISH and the quantitative PCR were analyzed.

RESULTS

Of these 76 persons with NB treated at one institution, 97 % are still alive, while 2 cases died from other diseases. Three patients experienced a recurrence after complete remission (CR), and 2 patients demonstrated refractory disease since the initial diagnosis. Two of the 3 NB patients with recurrence have demonstrated a 2nd CR, while one case still has multiple active diseases. Regarding the findings of highly sensitive biological analyses, 5/74 (7 %) showed MYCN amplification, 2/24 (8 %) cases had a 1p deletion, 3/33 (9 %) cases had a 17q gain, 5/50 (10 %) cases had diploidy, 1/25 (4 %) cases had a low expression of TRKA, and 2/76 (3 %) cases had an unfavorable histology. Of the 76 NB, 13 tumors (17 %) had one or more unfavorable factors (UF). Of the 5 refractory NB, 1 case had 3 UF, 1 case had 2 UF, 1 case had 1 UF, and 2 cases had no UF. As a result, 60 % of the refractory NB had one or more UF.

CONCLUSIONS

Of the NB detected by MS at one institution in Japan, 17 % had one or more unfavorable factors (UF) and might have a higher risk of recurrence than the patients with no UF, although the unfavorable biology of several refractory cases is still unclear even after highly sensitive analyses. At least one-fifth of the NB cases detected by MS are anticipated cases. In infantile neuroblastomas, it may therefore be most important to analyze biologically prognostic factors using highly sensitive methods followed by immediate surgical intervention. Since the MS program has been discontinued in Japan, it will be necessary in future to assess the mortality and characteristics of NB detected clinically.