Absolute Neutrophil Count after the First Chemotherapy Cycle as a Surrogate Marker for Treatment Outcomes in Patients with Neuroblastoma

Impact of 10% Dose Reductions and Duration of Treatment Delays in the Management of Chemotherapy-Induced Neutropenia in Dogs Treated With Common Chemotherapy Protocols: A Single-Centre Experience

Neutropenia is a common chemotherapy-associated adverse event (AE) in dogs and a significant cause of decreased relative dose intensity. Dose reductions (DRs) and treatment delays (TDs) are frequently applied to decrease the risk of further neutropenic events (NEs) and AEs, but there is no standardised approach. The two main objectives of this retrospective study were to determine: (1) the failure rate of a 10% DR to prevent a subsequent inadequate absolute neutrophil count (ANC), defined as a nadir ANC <0.75 × 109/L or pretreatment ANC <1.5 × 109/L; and (2) if the duration of TDs due to pretreatment neutropenia affects the occurrence of subsequent NEs. A total of 1056 chemotherapy treatments were recorded for 128 dogs that developed at least one NE. In 75 of 124 (60.5%, 95% CI: 51.2%-69%) evaluable NEs, a nadir ANC of ≥0.75 × 109/L and pretreatment ANC of ≥1.5 × 109/L were achieved after a single 10% chemotherapy DR, while a 10% DR failed to prevent a subsequent inadequate ANC in the remaining 49/124 (39.5%, 95% CI: 30.1%-48.3%). The only variable associated with failure was the drug prescribed. DR failure occurred in 22/39 (56.4%, 95% CI: 40.9%-70.6%) lomustine DRs, 14/27 (51.9%, 95% CI: 33.9%-69.2%) cyclophosphamide DRs, but only 2/22 (9.1%, 95% CI: 2.5%-27.8%) doxorubicin DRs and 2/24 (8.3%, 95% CI: 2.3%-25.8%) vincristine DRs. Seventy-three evaluable TDs (mean: 5 days, SD ± 2.2 days) were prescribed. There was no association between TD duration and subsequent NEs (p = 0.11).

Targeting the myeloid microenvironment in neuroblastoma

Myeloid cells (granulocytes and monocytes/macrophages) play an important role in neuroblastoma. By inducing a complex immunosuppressive network, myeloid cells pose a challenge for the adaptive immune system to eliminate tumor cells, especially in high-risk neuroblastoma. This review first summarizes the pro- and anti-tumorigenic functions of myeloid cells, including granulocytes, monocytes, macrophages, and myeloid-derived suppressor cells (MDSC) during the development and progression of neuroblastoma. Secondly, we discuss how myeloid cells are engaged in the current treatment regimen and explore novel strategies to target these cells in neuroblastoma. These strategies include: (1) engaging myeloid cells as effector cells, (2) ablating myeloid cells or blocking the recruitment of myeloid cells to the tumor microenvironment and (3) reprogramming myeloid cells. Here we describe that despite their immunosuppressive traits, tumor-associated myeloid cells can still be engaged as effector cells, which is clear in anti-GD2 immunotherapy. However, their full potential is not yet reached, and myeloid cell engagement can be enhanced, for example by targeting the CD47/SIRPα axis. Though depletion of myeloid cells or blocking myeloid cell infiltration has been proven effective, this strategy also depletes possible effector cells for immunotherapy from the tumor microenvironment. Therefore, reprogramming of suppressive myeloid cells might be the optimal strategy, which reverses immunosuppressive traits, preserves myeloid cells as effectors of immunotherapy, and subsequently reactivates tumor-infiltrating T cells.