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Simple Summary: Neuroblastoma (NB) presents with two patterns of disease: with or without metastasis. Both types of disease presentation include tumors with high-risk (HR) features. The management of HR-NB includes chemotherapy, surgery, radiotherapy, and anti-GD2 immunotherapy. Anti-GD2 monoclonal antibodies (mAbs) have significantly improved the outcome of HR-NB patients but they are mostly effective against disease affecting the bone and/or bone marrow (known as the osteomedullary compartment), and less so against soft tissue disease. The question arises as to whether anti-GD2 immunotherapy might benefit HR-NB patients with disease compounded by only soft tissue. In this retrospective review, we found that achieving first complete remission with chemotherapy, surgery, and radiotherapy does not prevent the risk of relapse. However, adding anti-GD2 mAbs once the patient has achieved complete remission significantly decreases the chances of relapse by 80%. Our study provides further support to indicate anti-GD2 mAbs in all cases with HR-NB. Neuroblastoma presents with two patterns of disease: locoregional or systemic. The poor prognostic risk factors of locoregional neuroblastoma (LR-NB) include age, MYCN or MDM2-CDK4 amplification, 11q, histology, diploidy with ALK or TERT mutations, and ATRX aberrations. Anti-GD2 immunotherapy has significantly improved the outcome of high-risk (HR) NB and is mostly effective against osteomedullary minimal residual disease (MRD), but less so against soft tissue disease. The question is whether adding anti-GD2 monoclonal antibodies (mAbs) benefits patients with HR-NB compounded by only soft tissue. We reviewed 31 patients treated at SJD for HR-NB with no osteomedullary involvement at diagnosis. All tumors had molecular genetic features of HR-NB. The outcome after first-line treatment showed 25 (80.6%) patients achieving CR. Thirteen patients remain in continued CR, median follow-up 3.9 years. We analyzed whether adding anti-GD2 immunotherapy to first-line treatment had any prognostic significance. The EFS analysis using Cox models showed a HR of 0.20, p = 0.0054, and an 80% decrease in the risk of relapse in patients treated with anti-GD2 immunotherapy in the first line. Neither EFS nor OS were significantly different by CR status after first-line treatment. In conclusion, adding treatment with anti-GD2 mAbs at the stage of MRD helps prevent relapse that unequivocally portends poor survival. [ABSTRACT FROM AUTHOR]

Simple Summary: Patients with high-risk neuroblastoma who are unable to achieve a complete response to induction chemotherapy are known as primary refractory and have poor outcomes. We investigated the combination of chemotherapy (irinotecan (I) and temozolomide (T)) plus anti-GD2 immunotherapy (naxitamab and sargramostim (GM-CSF)), the so-called HITS, against primary resistant high-risk neuroblastoma. Patients were treated when they had measurable chemo-resistant disease at the end of induction treatment but no evidence of progressive disease. Each cycle of HITS comprised Irinotecan 50 mg/m2/day intravenously plus Temozolomide 150 mg/m2/day orally (days 1–5); naxitamab 2.25 mg/kg/day IV on days 2, 4, 8 and 10, (total 9 mg/kg or 270 mg/m2 per cycle), and GM-CSF 250 mg/m2/day subcutaneously, for days 6–10 was used. Thirty-four patients received a median of four cycles. Treatment was outpatient and, overall, well tolerated. Patients treated with HITS immediately after induction failure (cohort 1 or early treatment) had a statistically significant improved survival rate compared to patients treated late (cohort 2). In summary, naxitamab-based chemo-immunotherapy is effective against primary chemo-resistant neuroblastoma, significantly improving long-term outcomes when administered early during the course of treatment. Patients with high-risk neuroblastoma (HR-NB) who are unable to achieve a complete response (CR) to induction therapy have worse outcomes. We investigated the combination of humanized anti-GD2 mAb naxitamab (Hu3F8), irinotecan (I), temozolomide (T), and sargramostim (GM-CSF)—HITS—against primary resistant HR-NB. Eligibility criteria included having a measurable chemo-resistant disease at the end of induction (EOI) treatment. Patients were excluded if they had progressive disease (PD) during induction. Prior anti-GD2 mAb and/or I/T therapy was permitted. Each cycle, administered four weeks apart, comprised Irinotecan 50 mg/m2/day intravenously (IV) plus Temozolomide 150 mg/m2/day orally (days 1–5); naxitamab 2.25 mg/kg/day IV on days 2, 4, 8 and 10, (total 9 mg/kg or 270 mg/m2 per cycle), and GM-CSF 250 mg/m2/day subcutaneously was used (days 6–10). Toxicity was measured using CTCAE v4.0 and responses through the modified International Neuroblastoma Response Criteria (INRC). Thirty-four patients (median age at treatment initiation, 4.9 years) received 164 (median 4; 1–12) HITS cycles. Toxicities included myelosuppression and diarrhea, which was expected with I/T, and pain and hypertension, expected with naxitamab. Grade ≥3-related toxicities occurred in 29 (85%) of the 34 patients; treatment was outpatient. The best responses were CR = 29% (n = 10); PR = 3% (n = 1); SD = 53% (n = 18); PD = 5% (n = 5). For cohort 1 (early treatment), the best responses were CR = 47% (n = 8) and SD = 53% (n = 9). In cohort 2 (late treatment), the best responses were CR = 12% (n = 2); PR = 6% (n = 1); SD = 53% (n = 9); and PD = 29% (n = 5). Cohort 1 had a 3-year OS of 84.8% and EFS 54.4%, which are statistically significant improvements (EFS p = 0.0041 and OS p = 0.0037) compared to cohort 2. In conclusion, naxitamab-based chemo-immunotherapy is effective against primary chemo-resistant HR-NB, increasing long-term outcomes when administered early during the course of treatment. [ABSTRACT FROM AUTHOR]