Biologic Prognostic Markers

The absence of cortical bone and extensive bone marrow metastatic involvement in a young neuro-blastoma patient should cause a shift in attention to biologic prognostic markers, including the three currently used to denote intermediate risk (Table 11.2.1). MYCN amplification is a particularly reliable predictor of aggressive disease. This chromosomal aberration is, therefore, not present in any subset of intermediate-risk neuroblastoma; however, the presence of three to nine copies of this proto-oncogene can result from whole chromosome gains (i.e., hyper-diploidy). At the present time the clinical significance of the gain of MYCN genes by this mechanism remains unclear.

The role of the Shimada histopathology system in defining intermediate-risk cases is limited to stage 4S and to stage 3 in patients more than 1 year old; thus, unfavorable histopathology places non-MYCN-ampli-fied stage-4S disease in the intermediate-risk, rather than the low-risk, category, while favorable histopa-thology places children with non-MYCN-amplified stage-3 tumors in the intermediate-risk, rather than the high-risk, category. The DNA index is relevant to the intermediate-risk category for non-MYCN-ampli-fied stage-4S tumors, with diploidy separating intermediate-risk from low-risk disease. Within the intermediate-risk category, histopathology and DNA index distinguish the favorable vs the unfavorable biology subsets, with the former treated with fewer cycles of chemotherapy than the latter in the current COG study.

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