Image-Defined Risk Factors

Image-defined risk factors (IDRFs) describe the preoperative radiological features and the relationship between the primary tumor mass and surrounding vessels and organs. They can help the physicians in deciding whether an initial safe, non-mutilating, and complete tumor excision is feasible or not. IDRFs were first analyzed in patients registered in SIOPEN LNESG1 study on localized non-MYCN-amplified NBL: the analysis showed that presence of one or more of these factors was associated with higher frequencies of primary incomplete excision, surgical-related complications, as well as lower survival. Their importance has been confirmed also when tumor excisions are done with minimal invasive surgery or after neoadjuvant chemotherapy. Since the accurate imaging studies on involvement of vessels and infiltration of adjacent tissues are a critical part of the radiological report, special guidelines have been established to optimize and uniform the radiological descriptions, including specific definitions recommended. The value of IDRF has been confirmed by the fact that they represent the basis of a pretreatment staging system (INRGSS), mainly important for localized NBL. INRGSS was developed by consensus among international experts on the background of large statistical analyses and then accepted by most cooperative groups. Currently it is used in parallel with INSS.