Evaluation of pseudoprogression in patients with glioblastoma multiforme using dynamic magnetic resonance imaging with ferumoxytol calls RANO criteria into question

Background

Diagnosis of pseudoprogression in patients with glioblastoma multiforme (GBM) is limited by Response Assessment in Neuro-Oncology (RANO) criteria to 3 months after chemoradiotherapy (CRT). Frequency of pseudoprogression occurring beyond this time limit was determined. Survival comparison was made between pseudoprogression and true progression patients as determined by using perfusion magnetic resonance imaging with ferumoxytol (p-MRI-Fe).

Methods

Fifty-six patients with GBM who demonstrated conventional findings concerning for progression of disease post CRT were enrolled in institutional review board-approved MRI protocols. Dynamic susceptibility-weighted contrast-enhanced p-MRI-Fe was used to distinguish true progression from pseudoprogression using relative cerebral blood volume (rCBV) values. rCBV of 1.75 was assigned as the cutoff value. Participants were followed up using RANO criteria, and survival data were analyzed.

Results

Twenty-seven participants (48.2%) experienced pseudoprogression. Pseudoprogression occurred later than 3 months post CRT in 8 (29.6%) of these 27 participants (ie, 8 [14.3%] of the 56 patients meeting the inclusion criteria). Overall survival was significantly longer in participants with pseudoprogression (35.2 months) compared with those who never experienced pseudoprogression (14.3 months; P < .001).

Conclusions

Pseudoprogression presented after 3 months post CRT in a considerable portion of patients with GBM, which raises doubts about the value of the 3-month time limit of the RANO criteria. Accurate rCBV measurement (eg, p-MRI-Fe) is suggested when there are radiographical concerns about progression of disease in GBM patients, regardless of any time limit. Pseudoprogression correlates with significantly better survival outcomes.     

Safety and technique of ferumoxytol administration for MRI

Ferumoxytol is an ultrasmall superparamagnetic iron oxide agent marketed for the treatment of anemia. There has been increasing interest in its properties as an MRI contrast agent as well as greater awareness of its adverse event profile. This mini‐review summarizes the current state of knowledge of the risks of ferumoxytol and methods of administration. Magn Reson Med 75:2107–2111, 2016. © 2016 Wiley Periodicals, Inc.     

From the Cover: In vivo imaging of nanoparticle-labeled CAR T cells

Metastatic osteosarcoma has a poor prognosis with a 2-y, event-free survival rate of ∼15 to 20%, highlighting the need for the advancement of efficacious therapeutics. Chimeric antigen receptor (CAR) T-cell therapy is a potent strategy for eliminating tumors by harnessing the immune system. However, clinical trials with CAR T cells in solid tumors have encountered significant challenges and have not yet demonstrated convincing evidence of efficacy for a large number of patients. A major bottleneck for the success of CAR T-cell therapy is our inability to monitor the accumulation of the CAR T cells in the tumor with clinical-imaging techniques. To address this, we developed a clinically translatable approach for labeling CAR T cells with iron oxide nanoparticles, which enabled the noninvasive detection of the iron-labeled T cells with magnetic resonance imaging (MRI), photoacoustic imaging (PAT), and magnetic particle imaging (MPI). Using a custom-made microfluidics device for T-cell labeling by mechanoporation, we achieved significant nanoparticle uptake in the CAR T cells, while preserving T-cell proliferation, viability, and function. Multimodal MRI, PAT, and MPI demonstrated homing of the T cells to osteosarcomas and off-target sites in animals administered with T cells labeled with the iron oxide nanoparticles, while T cells were not visualized in animals infused with unlabeled cells. This study details the successful labeling of CAR T cells with ferumoxytol, thereby paving the way for monitoring CAR T cells in solid tumors.

Clinical advances in the treatment of osteosarcoma have reached a plateau, and the survival rate has remained stagnant for over two decades (1). The prognosis for children with refractory, relapsed, and metastasized osteosarcoma remains poor with typically a 2-y event-free survival rate of 15 to 20% (2). Therefore, new therapeutics are urgently needed. Recent studies have shown promising results using chimeric antigen receptor (CAR) T cells that were targeted to the immune checkpoint molecule B7-H3 (CD276), a tumor antigen that is significantly up-regulated in osteosarcoma (3). The molecule is a member of the B7 and CD28 families and is broadly expressed on tumor cells, in which it is thought to play an inhibitory role on T-cell function (4).CD19-targeted CAR T-cell therapies have demonstrated remarkable efficacy in the treatment of CD19-expressing tumors as well as in advanced, chemotherapy-resistant leukemia and lymphoma (5–7). However, responses in patients receiving T-cell therapy have been variable (8–10). A diagnostic technique that could noninvasively monitor the localization and expansion of the CAR T cells in tumors and off-target sites would help optimize personalized treatment regimens and combination therapies. Strategies used by clinical investigators to assess the activity of infused CAR T cells consist of flow cytometry, immunohistochemistry, and qPCR of peripheral blood samples or biopsies of sites of CAR T-cell activity including bone marrow, tumors, and lymph nodes (9, 10). While they provide suitable information, flow cytometry measurements of the expression of the CAR gene in circulating T cells represents the response in the periphery and not the tumor site (11), and repeated invasive biopsies are not practical in most clinical trials (12).Magnetic resonance imaging (MRI) (13–15) and positron emission tomography (PET) (16–18) have been used to visualize therapeutic T cells in human subjects. Ahrens and coworkers used perfluorocarbon emulsion to label CAR T cells expressing antiepidermal growth factor receptor variant III (EGFRvIII), and they quantified the labeling of the T cells using fluorine-19 NMR after intravenous injection of the CAR T cells in mice bearing U87-EGFRvIII tumors (19). Additionally, imaging of EGFRvIII CAR T cells labeled with ultrasmall superparamagnetic iron oxide nanoparticles trafficking to human U-87 MG glioblastomas (20) and ferucarbotran-labeled, pmel-specific DsRed T cells accumulating in murine KR158B luciferase expressing glioblastomas (21) has also been reported. Furthermore, others have used enzymes (22), transporters (23), or membrane proteins (24) that facilitated the accumulation of radiotracers, for example, 9-(4-[¹⁸F]fluoro-3-(hydroxymethyl) butyl)guanine in glioblastoma (17, 25). This requires genetic modification of the therapeutic cells, which, using previous viral packaging capacity, can result in immunogenicity and could potentially interfere with their function (26).An ideal method for imaging intravenously infused CAR T cells should 1) utilize a widely available clinical-imaging technique, 2) use a translatable-imaging agent, 3) be nonimmunogenic, 4) provide low background in off-target tissues, and 5) provide quantitative measurements. To address these requirements, we developed a MRI-based cell-tracking technique, because MRI is already routinely used to monitor osteosarcomas in patients. We used the Food and Drug Administration (FDA)–approved iron supplement, ferumoxytol, “off label” as a cell marker, because ferumoxytol is composed of iron oxide nanoparticles that can be detected with MRI (27). Administration of ferumoxytol nanoparticles in children and young adults did not result in any signs of liver toxicity, hematologic, or kidney impairments (28); therefore, it is safe to use in humans. Ferumoxytol nanoparticles can also be detected with magnetic particle imaging (MPI), which provides high target to background contrast (29) and quantitative measurements (30).Other therapeutic cells have been detected with ferumoxytol MRI in rodents (31–33), porcine animal models (34), and patients (28). However, no group has successfully labeled and tracked CAR T cells in vivo with ferumoxytol thus far. This is because transfection agents that are usually used to shuttle iron oxide nanoparticles into target cells, show low efficiency in T cells (35–37), and should be avoided for clinical applications (35). We used a custom-made microfluidics device (38) for mechanoporation-labeling of human anti-B7-H3 CAR T cells with ferumoxytol. This mechanical-labeling method does not require transfection agents or genetic manipulation of the cells.The goal of our study was to develop a clinically translatable approach to label CAR T cells with nanoparticles for noninvasive cell-tracking using MRI, photoacoustic imaging (PAT), and MPI, while confirming cell viability with bioluminescence imaging (BLI). We demonstrated the detection of ferumoxytol-labeled CAR T cells localizing in osteosarcomas using MRI, PAT, and MPI, paving the way for clinical translation of this approach.