Postchemotherapy gross residual tumor in non-high-risk neuroblastoma: Clinical significance and the role of adjuvant therapy

Background: Although survival rate among patients with non-high-risk neuroblastoma is excellent, a gross residual tumor (GRT) is often present at the end of treatment. However, reliable data do not exist on the relevance of a GRT for the risk of progression and the role of adjuvant therapy for patients with GRT. Methods: A retrospective review of 131 patients with non-high-risk neuroblastoma who underwent chemotherapy was performed. GRT was defined as >1 cm³ residual soft tissue density on end-of-chemotherapy scans. Progression-free survival (PFS) and overall survival (OS) rates were compared between patients with GRT and those without GRT. A proportional hazards model was also used to assess the effects of GRT and adjuvant therapies, including radiation and isotretinoin therapy on outcomes. Results: GRT was found in 52 (40%) patients in the study cohort. Correlation was not found between GRT and outcomes (PFS; p =.954, OS; p =.222). In multivariable analysis, GRT remained a nonsignificant predictor of outcome after adjusting for confounders. Local radiation and isotretinoin therapy did not affect outcome for patients with GRT. However, within GRT subgroups, the degree of volume reduction, as well as absolute residual volume in the primary tumor after induction treatment, were significantly associated with outcomes. Conclusion: GRT in non-high-risk neuroblastoma may not indicate active disease that requires additional treatment. However, risk of progression is increased in patients with GRT whose response to treatment was less prominent, thus adjuvant therapy should be reserved only for those patients.