Blood Test Clue: Monocyte Recovery During Glioblastoma Treatment Predicts Longer Survival

For patients with glioblastoma, the most aggressive and common primary brain cancer in adults, the standard of care has remained stubbornly unchanged for two decades: surgical resection followed by radiotherapy with concurrent and adjuvant temozolomide chemotherapy. Even with this intensive regimen, median survival hovers around 15 to 18 months, and clinicians have long relied on a handful of established prognostic factors—age, performance status, the extent of surgical resection, and methylation status of the MGMT promoter—to guide expectations and treatment decisions. Now, a new study published in the Journal of Neuro-Oncology suggests that a remarkably simple source of prognostic information may have been sitting in plain sight all along: the routine complete blood count drawn before and after the six-week course of chemoradiotherapy.

The research, led by Flavio Donnini and Paolo Tini at the University of Siena in collaboration with investigators across multiple Italian institutions, focused not on static pretreatment values, which most prior studies have examined, but on the dynamic trajectory of circulating monocytes during treatment itself. The team defined a metric they call monocytic resilience: the log2-transformed ratio of the absolute monocyte count measured at the end of chemoradiotherapy to the count measured before treatment began. In essence, the measure captures whether a patient’s monocyte compartment is preserved, depleted, or expanded by the combined assault of radiation and chemotherapy—a biological signature of how the host immune system weathers one of the most demanding treatment courses in oncology.

The retrospective cohort included 127 adults with histologically confirmed IDH-wildtype glioblastoma, the molecularly defined subtype that carries the poorest prognosis and accounts for the vast majority of glioblastoma diagnoses in adults. Of these, 115 patients had complete monocyte trajectories and overall survival data, and the primary adjusted statistical model encompassed 102 patients among whom 86 deaths occurred. The investigators deliberately designed their analysis to ask whether the monocyte ratio carried prognostic weight beyond the factors clinicians already use, adjusting their models for MGMT promoter methylation, gross total resection, Karnofsky Performance Status, and age, and additionally accounting for baseline monocyte burden, changes in lymphocyte counts, systemic inflammatory imbalance, and measured corticosteroid exposure.

The results were striking. When analyzed as a continuous variable, the post-treatment to pre-treatment monocyte ratio was independently associated with overall survival, with a hazard ratio of 0.53 per doubling of the ratio (95 percent confidence interval 0.37 to 0.76; p = 0.00051). In practical terms, each doubling of the monocyte ratio was associated with nearly a halving of the risk of death during the observation period, an effect size that rivals or exceeds many molecular biomarkers currently in clinical use. The signal survived every adjustment the investigators applied, suggesting that the preservation of circulating monocytes during treatment reflects a genuine host-response phenotype rather than a statistical artifact of tumor aggressiveness or treatment intensity.

To make the finding clinically interpretable, the team also evaluated an exploratory threshold: a post/pre ratio of 0.75, meaning that patients whose end-of-treatment monocyte count remained at or above 75 percent of their pretreatment value were classified as having preserved monocytic resilience. Using this cutoff, 52 patients fell into the low-resilience group and 63 into the preserved-resilience group. The separation in survival was dramatic: median overall survival was 10.2 months in the low-resilience group compared with 17.3 months in the preserved-resilience group, a difference of roughly seven months detected with a log-rank p value of 0.00064. In univariable Cox analysis, preserved resilience was associated with a 50 percent reduction in mortality (hazard ratio 0.50, 95 percent confidence interval 0.34 to 0.75; p = 0.00080).

Importantly, the investigators were careful about how they handled the threshold itself. Recognizing the well-documented statistical pitfalls of dichotomizing continuous variables, they treated the continuous ratio as the primary basis for inference and used the 0.75 cutoff only for exploratory visualization and sensitivity analysis. They also employed bootstrap resampling to probe whether the apparent threshold was an artifact of their particular dataset. The outcome-optimized cut-points clustered tightly around the same region, with a median of 0.74 and an interquartile range of 0.70 to 0.81, lending credibility to the choice of 0.75 as a clinically meaningful boundary—while the authors explicitly caution that the threshold remains exploratory and requires external validation before any clinical application.

The biological rationale behind the finding is grounded in a growing body of literature on systemic immune perturbation in glioblastoma. Monocytes are innate immune cells that circulate in the blood and give rise to macrophages, including the tumor-associated macrophages and microglia that can constitute up to a third of the cellular mass of a glioblastoma. Prior work has shown that glioblastoma patients exhibit profound systemic immune suppression, including an expansion of immunosuppressive CD14-positive HLA-DR-low monocytes, and that dexamethasone—the corticosteroid nearly universally prescribed to control peritumoral edema—reshapes the monocyte compartment in ways that may promote tumor progression. Studies have also demonstrated that T cells become sequestered in the bone marrow in the setting of intracranial tumors, and that treatment-induced lymphopenia during chemoradiotherapy is strongly associated with worse survival, partly driven by radiation exposure of circulating blood and by cumulative corticosteroid dose.

What makes the new finding conceptually distinct is that it isolates the monocyte lineage from the lymphocyte story that has dominated the field. The Siena team adjusted for lymphocyte change and for systemic inflammatory indices, yet the monocyte ratio retained its independent association with survival. This suggests that monocytic resilience is not simply a proxy for overall bone marrow reserve or for the degree of treatment-related immunosuppression, but may capture something specific about the interplay between the tumor, the treatment, and the innate immune system. Whether preserved monocytes reflect a less inflammatory tumor microenvironment, a more favorable corticosteroid exposure profile, an intrinsic host capacity to regenerate myeloid cells, or some combination of these mechanisms remains an open question that the authors themselves flag as requiring immune phenotyping studies.

The practical appeal of the metric is difficult to overstate. Unlike genomic classifiers or advanced imaging biomarkers, absolute monocyte counts are obtained routinely, inexpensively, and reproducibly in every complete blood count. A patient undergoing the standard Stupp regimen already has blood drawn before treatment and at its conclusion, meaning that monocytic resilience could, in principle, be calculated from data that already exist in the medical record. If validated prospectively, the measure could help stratify patients for clinical trials, identify individuals who might benefit from intensified surveillance or adaptive treatment strategies, and provide an early pharmacodynamic readout of how a patient’s immune system is responding to therapy—information that currently arrives far too late in the form of surveillance MRI.

The authors are appropriately measured in their conclusions. This was a retrospective, single-country cohort study, and the exploratory threshold of 0.75 has not been tested in an independent population. Medication-level confounder assessment—particularly granular corticosteroid dosing data—and prospective validation in external cohorts are explicitly required before the metric can inform clinical decisions. Yet the study exemplifies a broader and increasingly exciting trend in neuro-oncology: the recognition that the peripheral immune system is not a passive bystander in brain cancer but an active participant whose dynamics over time encode prognostic information. As immunotherapeutic strategies for glioblastoma continue to struggle in clinical trials, simple, dynamic, and accessible markers of host immune resilience such as this one may prove essential not only for prognosis but for rationally selecting which patients might benefit from the next generation of immune-based treatments.

Subject of Research: Monocyte count trajectories during chemoradiotherapy as a prognostic biomarker for survival in IDH-wildtype glioblastoma

Article Title: Monocytic resilience during chemoradiotherapy is independently associated with survival in IDH-Wildtype glioblastoma

Article References: Monocytic resilience during chemoradiotherapy is independently associated with survival in IDH-Wildtype glioblastoma. (n.d.). https://doi.org/10.1007/s11060-026-05830-x

Image Credits: AI Generated

DOI: 10.1007/s11060-026-05830-x

Keywords: glioblastoma, monocytes, immune resilience, chemoradiotherapy, biomarkers, survival, corticosteroids, temozolomide, prognosis, neuro-oncology, blood counts, MGMT methylation