Dexamethasone May Nix Immunotherapy Benefit in Glioblastoma

Mark L. Fuerst

December 23, 2020

Dexamethasone can have a detrimental effect on survival in patients with glioblastoma who are receiving immunotherapy, according to a study published in Clinical Cancer Research.

Investigators found that baseline dexamethasone use was associated with poor overall survival (OS) in glioblastoma patients receiving anti–PD-1 or anti–PD-L1 therapy. In fact, in a multivariable analysis, baseline dexamethasone use was the strongest predictor of poor survival.

These results "support accumulating concerns that corticosteroids can be detrimental to immunotherapy for oncology patients," wrote senior study author David Reardon, MD, of Dana-Farber Cancer Institute in Boston and colleagues.

The concerns are particularly relevant for glioblastoma patients because dexamethasone is a cornerstone of glioblastoma therapy, being used to reduce tumor-associated edema. Patients often receive dexamethasone early on and in significant doses for a protracted period of time to stay ahead of evolving symptoms.

However, the current study suggests dexamethasone and other corticosteroids may be contraindicated in glioblastoma patients on immunotherapy. Therefore, Reardon and colleagues recommended "careful evaluation of dexamethasone use" in these patients.

"If a glioblastoma patient requires corticosteroids, and they often do for debilitating symptoms, only use these drugs if the patient really needs them," Reardon advised. "Start at a low dose and use the shortest treatment interval possible."

Preclinical and Clinical Results

Reardon and colleagues initially evaluated the effects of dexamethasone when administered with PD-1 blockade and/or radiotherapy in an immunocompetent syngeneic mouse model.

Most mice that received anti–PD-1 monotherapy were cured, but the benefit of anti–PD-1 therapy was significantly diminished, in a dose-dependent manner, when dexamethasone was added.

At 100 days, the OS rate was about 76% in the anti–PD-1 monotherapy group, 47% when dexamethasone was given at 1 mg/kg, 31% with dexamethasone at 2.5 mg/kg, and 27% with dexamethasone at 10 mg/kg.

A mechanistic study, including analysis of immune cells in the spleen, showed that dexamethasone decreased intratumoral T cells and systemic levels of T cells, natural killer cells, and myeloid cells, while qualitatively impairing lymphocyte function. The mechanism of T-cell depletion included induction of apoptosis, which was noted as soon as 1 hour after the dexamethasone dose, Reardon said.

The researchers also evaluated 181 consecutive glioblastoma patients treated with PD-1– or PD-L1–targeted therapy. The study included a multivariable statistical analysis that accounted for age, performance status, extent of resection, size of tumor, bulk tumor burden, and MGMT promoter methylation status.

In an initial unadjusted analysis, baseline dexamethasone decreased the median OS to 8.1 months when it was given at less than 2 mg daily and 6.3 months when given at 2 mg or more daily. The median OS was 13.1 months for patients who did not receive dexamethasone.

After multivariable adjustment, baseline dexamethasone eliminated the survival benefit of immunotherapy, the researchers said. The hazard ratio was 2.16 (P = .003) when dexamethasone was given at less than 2 mg daily and 1.97 (P = .005) with dexamethasone at 2 mg or more daily, compared with no baseline dexamethasone.

In fact, the strongest negative risk factor for OS was the use of dexamethasone at initiation of checkpoint inhibitor therapy.

Implications: Use Corticosteroids 'Very Judiciously'

The results of this research suggest "corticosteroids can be detrimental when used along with checkpoint inhibitors," Reardon said. He added that this effect could extend to other immunotherapies, such as vaccines, cellular therapies, and oncolytic viruses.

"We need to understand what is driving the inflammatory response," Reardon said. "Other targets in the downstream pathway may be regulated to avoid the detrimental effect of corticosteroids."

Ongoing prospective clinical trials need to build in whether concurrent use of corticosteroids leads to poorer outcomes, according to Reardon.

"We are validating this prospectively in ongoing clinical trials to evaluate differences in outcome in glioblastoma patients and exploring different types of immunotherapies," he said.

Though questions remain, Reardon advises judicious use of corticosteroids or even substituting corticosteroids with bevacizumab in glioblastoma patients.

"If a glioblastoma patient develops debilitating symptoms due to swelling in the brain and is a candidate for immunotherapy, then consider using bevacizumab to avoid using corticosteroids," Reardon said, adding that this is being tested prospectively in a clinical trial as well.

"We know corticosteroids have a host of side effects. An additional side effect may be limiting immune function in brain cancer patients and jeopardizing the potential benefits of immunotherapy going forward. I implore practicing oncologists to use corticosteroids very judiciously and as little as possible for as little time as possible," Reardon said.

This research was funded by grants from the National Institutes of Health and support from various foundations and institutions. The researchers disclosed relationships with many pharmaceutical companies.

SOURCE: Iorgulescu JB et al. Clin Cancer Res. 2020 Nov 25. doi: 10.1158/1078-0432.CCR-20-2291.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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