Table 1.

Clinical and molecular characteristics of neuroblastoma patient tumors^*

Clinical characteristic	No. of patients
	MYCN amplification		ABCC1 expression		ABCC3 expression		ABCC4 expression
	Present	Absent	High	Low	High	Low	High	Low
Age†
<1 y	3	93	12	84	87	8	9	87
>1 y	20	91	8	104	67	45	11	101
Tumor stage‡
Favorable	1	105	8	98	87	18	6	100
Unfavorable	22	65	12	76	56	32	14	74

^*Two hundred and nine study patients; Categories are overlapping. MYCN amplification was considered absent if there were nine or fewer FISH signals for MYCN per tumor cell and present if there were more than nine signals. Status of two case patients was unknown. For ABCC1 and ABCC4, the level of expression was considered high or low in relation to the upper decile of ΔΔCt values for all tumors analyzed. For ABCC3, the level of expression was considered high or low in relation to the lower quartile of ΔΔCt values for all tumors analyzed. ΔΔCt method is the comparative threshold cycle method of transcript quantification. ABCC = ATP-binding cassette, subfamily C; FISH = Fluorescence in situ hybridization; MYCN = v-myc myelocytomatosis viral related oncogene, neuroblastoma derived.

^†Age (categorized as <1 or >1 year at diagnosis) was statistically significantly associated with MYCN amplification (P < .001) and with ABCC3 expression (P < .001) (Two-sided Fisher exact tests). Age was unknown for one patient.

^‡Tumor stage was categorized as favorable (INSS stages 1, 2A/2B, or 4S) or unfavorable (INSS stages 3 or 4) and was unknown in 15 case patients. Tumor stage was statistically significantly associated with MYCN amplification (P < .001), ABCC3 expression (P = .003), and ABCC4 expression (P = .03) (Two-sided Fisher’s exact tests). INSS = International Neuroblastoma Staging System.