Abstract
Simple SummaryThe anti-tumor activity of anti-GD2 monoclonal antibodies (mAbs) have been demonstrated by the capacity to mediate immunological cytotoxicity but also through direct cell death induction. Recently, studies with anti-GD2 mAbs for high-risk (HR)-neuroblastoma (NB) patients with measurable disease, with or without chemotherapy, have reported significant objective responses. In this subgroup of patients, we observed that, while being treated with the mAb naxitamab, some chemorefractory lesions showed long periods of stable disease. Here, we report a comprehensive imaging evaluation of those lesions correlating with histopathological demonstration of naxitamab-induced tissue differentiation. Our results suggest an undescribed mechanism of action for anti-GD2 mAbs.Background: Neuroblastic tumors (NBTs) originate from a block in the process of differentiation. Histologically, NBTs are classified in neuroblastoma (NB), ganglioneuroblastoma (GNB), and ganglioneuroma (GN). Current therapy for high-risk (HR) NB includes chemotherapy, surgery, radiotherapy, and anti-GD2 monoclonal antibodies (mAbs). Anti-GD2 mAbs induce immunological cytoxicity but also direct cell death. Methods: We report on patients treated with naxitamab for chemorefractory NB showing lesions with long periods of stable disease. Target lesions with persisting 123I-Metaiodobenzylguanidine (MIBG) uptake after 4 cycles of immunotherapy were further evaluated by functional Magnetic Resonance Imaging (MRI) and/or Fluorodeoxyglucose (FDG)-positron emission tomography (PET). MIBG avid lesions that became non-restrictive on MRI (apparent diffusion coefficient (ADC) > 1) and/or FDG-PET negative (SUV < 2) were biopsied. Results: Twenty-seven relapse/refractory (R/R) HR-NB patients were enrolled on protocol Ymabs 201. Two (7.5%) of the 27 showed persistent bone lesions on MIBG, ADC high, and/or FDG-PET negative. Forty-four R/R HR-NB patients received chemo-immunotherapy. Twelve (27%) of the 44 developed persistent MIBG+ but FDG-PET- and/or high ADC lesions. Twelve (86%) of the 14 cases identified were successfully biopsied producing 16 evaluable samples. Histology showed ganglioneuroma maturing subtype in 6 (37.5%); ganglioneuroma mature subtype with no neuroblastic component in 4 (25%); differentiating NB with no Schwannian stroma in 5 (31%); and undifferentiated NB without Schwannian stroma in one (6%). Overall, 10 (62.5%) of the 16 specimens were histopathologically fully mature NBTs. Conclusions: Our results disclose an undescribed mechanism of action for naxitamab and highlight the limitations of conventional imaging in the evaluation of anti-GD2 immunotherapy clinical efficacy for HR-NB.
Highlights
Neuroblastic tumors (NBTs) derive from neural crest cells and are the most common extracranial solid childhood tumors
Patients enrolled in this trial had refractory disease exclusively in the bone/bone marrow (BM) compartment by MIBG and/or conventional cytomorphology examination of the BM
Seven more patients (Table 1, pts #3–8 and 14) received immunotherapy according to the 201 protocol and received HITS cycles because of relapse or persistent/refractory disease FDG-positron emission tomography (PET) positive and/or DWI with low apparent diffusion coefficient (ADC) values
Summary
Neuroblastic tumors (NBTs) derive from neural crest cells and are the most common extracranial solid childhood tumors. The nuclei are round, with a salt-and-pepper appearance, and may contain distinct nucleoli In these undifferentiated tumors, immunohistochemistry shows a pattern compatible with immature ganglionic (neuronal) sympathetic nervous system lineage origin (Phox2b positive). GNB show mature Schwannian stromal component and well-defined microscopic foci of neuroblastic cells in various stages of differentiation. GN are composed of mature Schwannian stroma (>90% of the tumor tissue) and scattered neuroblastic cells, which include differentiating neuro-blasts and maturing or mature ganglion cells usually surrounded by satellite cells. Two (7.5%) of the 27 showed persistent bone lesions on MIBG, ADC high, and/or FDG-PET negative. 10 (62.5%) of the 16 specimens were histopathologically fully mature NBTs. Conclusions: Our results disclose an undescribed mechanism of action for naxitamab and highlight the limitations of conventional imaging in the evaluation of anti-GD2 immunotherapy clinical efficacy for HR-NB
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