Development of novel therapies for CNS tumors requires reliable assessment of response and progression. This requirement has been particularly challenging in neuro-oncology for which contrast enhancement serves as an imperfect surrogate for tumor volume and is influenced by agents that affect vascular permeability, such as antiangiogenic therapies. In addition, most tumors have a nonenhancing component that can be difficult to accurately quantify. To improve the response assessment in neuro-oncology and to standardize the criteria that are used for different CNS tumors, the Response Assessment in Neuro-Oncology (RANO) working group was established. This multidisciplinary international working group consists of neuro-oncologists, medical oncologists, neuroradiologists, neurosurgeons, radiation oncologists, neuropsychologists, and experts in clinical outcomes assessments, working in collaboration with government and industry to enhance the interpretation of clinical trials. The RANO working group was originally created to update response criteria for high- and low-grade gliomas and to address such issues as pseudoresponse and nonenhancing tumor progression from antiangiogenic therapies, and pseudoprogression from radiochemotherapy. RANO has expanded to include working groups that are focused on other tumors, including brain metastases, leptomeningeal metastases, spine tumors, pediatric brain tumors, and meningiomas, as well as other clinical trial end points, such as clinical outcomes assessments, seizures, corticosteroid use, and positron emission tomography imaging. In an effort to standardize the measurement of neurologic function for clinical assessment, the Neurologic Assessment in Neuro-Oncology scale was drafted. Born out of a workshop conducted by the Jumpstarting Brain Tumor Drug Development Coalition and the US Food and Drug Administration, a standardized brain tumor imaging protocol now exists to reduce variability and improve reliability. Efforts by RANO have been widely accepted and are increasingly being used in neuro-oncology trials, although additional refinements will be needed.

The RANO criteria have not been assessed using outcome data from prospective trials. We examined the radiologic data of patients with recurrent glioblastoma from the randomized phase II trial (AVF3708g) to determine the effect of including T2/FLAIR evaluation as per RANO criteria on measurements of objective response rates (ORRs) and progression-free survival (PFS) compared with assessment based on contrast enhancement (Macdonald criteria).The ORRs and median PFS were determined using the RANO criteria and compared with those obtained using the Macdonald criteria. Landmark analyses were performed at 2, 4, and 6 months, and Cox proportional hazard models were used to determine the associations between OR and progression with subsequent survival.The ORRs were 0.331 [95% confidence interval (CI), 0.260-0.409] and 0.393 (95% CI, 0.317-0.472) by RANO and Macdonald criteria, respectively (P < 0.0001). The median PFS was 4.6 months (95% CI, 4.1-5.5) using RANO criteria, compared with 6.4 months (95% CI, 5.5-7.1) as determined by Macdonald criteria (P = 0.01). At 2-, 4-, and 6-month landmarks, both OR status and PFS determined by either RANO or Macdonald criteria were predictive of overall survival [OS; hazard ratios for 4-month landmark (OR HR = 1.93, P = 0.0012; PFS HR, 4.23, P < 0.0001)].The inclusion of T2/FLAIR assessment resulted in statistically significant differences in median PFS and ORRs compared with assessment of solely enhancing tumor (Macdonald criteria), although OR and PFS determined by both RANO and Macdonald criteria correlated with OS.

Purpose

GDC-0084 is an oral, brain-penetrant small-molecule inhibitor of PI3K and mTOR. A first-in-human, phase I study was conducted in patients with recurrent high-grade glioma.

Patients and methods

GDC-0084 was administered orally, once daily, to evaluate safety, pharmacokinetics (PK), and activity. Fluorodeoxyglucose-PET (FDG-PET) was performed to measure metabolic responses.

Results

Forty-seven heavily pretreated patients enrolled in eight cohorts (2-65 mg). Dose-limiting toxicities included 1 case of grade 2 bradycardia and grade 3 myocardial ischemia (15 mg), grade 3 stomatitis (45 mg), and 2 cases of grade 3 mucosal inflammation (65 mg); the MTD was 45 mg/day. GDC-0084 demonstrated linear and dose-proportional PK, with a half-life (∼19 hours) supportive of once-daily dosing. At 45 mg/day, steady-state concentrations exceeded preclinical target concentrations producing antitumor activity in xenograft models. FDG-PET in 7 of 27 patients (26%) showed metabolic partial response. At doses ≥45 mg/day, a trend toward decreased median standardized uptake value in normal brain was observed, suggesting central nervous system penetration of drug. In two resection specimens, GDC-0084 was detected at similar levels in tumor and brain tissue, with a brain tissue/tumor-to-plasma ratio of >1 and >0.5 for total and free drug, respectively. Best overall response was stable disease in 19 patients (40%) and progressive disease in 26 patients (55%); 2 patients (4%) were nonevaluable.

Conclusions

GDC-0084 demonstrated classic PI3K/mTOR-inhibitor related toxicities. FDG-PET and concentration data from brain tumor tissue suggest that GDC-0084 crossed the blood-brain barrier.

Building on an initiative to enhance clinical trial participation involving the Society for Neuro-Oncology, the Response Assessment in Neuro-Oncology Working Group, patient advocacy groups, clinical trial cooperative groups, and other partners, we evaluate the impact of eligibility criteria and trial conduct on neuro-oncology clinical trial participation. Clinical trials often carry forward eligibility criteria from prior studies that may be overly restrictive and unnecessary and needlessly limit patient accrual. Inclusion and exclusion criteria should be evaluated based on the goals and design of the study and whether they impact patient safety and/or treatment efficacy. In addition, we evaluate clinical trial conduct as a barrier to accrual and discuss strategies to minimize such barriers for neuro-oncology trials.

The activity of single-agent targeted molecular therapies in glioblastoma has been limited to date. The North American Brain Tumor Consortium examined the safety, pharmacokinetics, and efficacy of combination therapy with sorafenib, a small molecule inhibitor of Raf, vascular endothelial growth factor receptor 2, and platelet-derived growth factor receptor-β, and temsirolimus (CCI-779), an inhibitor of mammalian target of rapamycin. This was a phase I/II study. The phase I component used a standard 3 × 3 dose escalation scheme to determine the safety and tolerability of this combination therapy. The phase II component used a 2-stage design; the primary endpoint was 6-month progression-free survival (PFS6) rate. Thirteen patients enrolled in the phase I component. The maximum tolerated dosage (MTD) for combination therapy was sorafenib 800 mg daily and temsirolimus 25 mg once weekly. At the MTD, grade 3 thrombocytopenia was the dose-limiting toxicity. Eighteen patients were treated in the phase II component. At interim analysis, the study was terminated and did not proceed to the second stage. No patients remained progression free at 6 months. Median PFS was 8 weeks. The toxicity of this combination therapy resulted in a maximum tolerated dose of temsirolimus that was only one-tenth of the single-agent dose. Minimal activity in recurrent glioblastoma multiforme was seen at the MTD of the 2 combined agents.

Therapeutic advances for glioblastoma have been minimal over the past 2 decades. In light of the multitude of recent phase III trials that have failed to meet their primary endpoints following promising preclinical and early-phase programs, a Society for Neuro-Oncology Think Tank was held in November 2020 to prioritize areas for improvement in the conduct of glioblastoma clinical trials. Here, we review the literature, identify challenges related to clinical trial eligibility criteria and trial design in glioblastoma, and provide recommendations from the Think Tank. In addition, we provide a data-driven context with which to frame this discussion by analyzing key study design features of adult glioblastoma clinical trials listed on ClinicalTrials.gov as "recruiting" or "not yet recruiting" as of February 2021.

Purpose

A phase I, dose-finding study of vorinostat in combination with temozolomide (TMZ) was conducted to determine the maximum tolerated dose (MTD), safety, and pharmacokinetics in patients with high-grade glioma (HGG).

Experimental design

This phase I, dose-finding, investigational study was conducted in two parts. Part 1 was a dose-escalation study of vorinostat in combination with TMZ 150 mg/m(2)/day for 5 days every 28 days. Part 2 was a dose-escalation study of vorinostat in combination with TMZ 150 mg/m(2)/day for 5 days of the first cycle and 200 mg/m(2)/day for 5 days of the subsequent 28-day cycles.

Results

In part 1, the MTD of vorinostat administered on days 1 to 7 and 15 to 21 of every 28-day cycle, in combination with TMZ, was 500 mg daily. Dose-limiting toxicities (DLT) included grade 3 anorexia, grade 3 ALT, and grade 5 hemorrhage in the setting of grade 4 thrombocytopenia. In part 2, the MTD of vorinostat on days 1 to 7 and 15 to 21 of every 28-day cycle, combined with TMZ, was 400 mg daily. No DLTs were encountered, but vorinostat dosing could not be escalated further due to thrombocytopenia. The most common serious adverse events were fatigue, lymphopenia, thrombocytopenia, and thromboembolic events. There were no apparent pharmacokinetic interactions between vorinostat and TMZ. Vorinostat treatment resulted in hyperacetylation of histones H3 and H4 in peripheral mononuclear cells.

Conclusion

Vorinostat in combination with temozolomide is well tolerated in patients with HGG. A phase I/II trial of vorinostat with radiotherapy and concomitant TMZ in newly diagnosed glioblastoma is underway.

Many factors contribute to the poor survival of malignant brain tumor patients, some of which are not easily remedied. However, one contributor to the lack of progress that may be modifiable is poor clinical trial accrual. Surveys of brain tumor patients and neuro-oncology providers suggest that clinicians do a poor job of discussing clinical trials with patients and referring patients for clinical trials. Yet, data from the Cancer Action Network of the American Cancer Society suggest that most eligible oncology patients asked to enroll on a clinical trial will agree to do so. To this end, the Society for Neuro-Oncology (SNO) in collaboration with the Response Assessment in Neuro-Oncology (RANO) Working Group, patient advocacy groups, clinical trial cooperative groups, including the Adult Brain Tumor Consortium (ABTC), and other partners are working together with the intent to double clinical trial accrual over the next 5 years. Here we describe the factors contributing to poor clinical trial accrual in neuro-oncology and offer possible solutions.

Glioblastoma is the most common primary malignant brain tumor in adults and is associated with poor survival. The Ivy Foundation Early Phase Clinical Trials Consortium conducted a randomized, multi-institution clinical trial to evaluate immune responses and survival following neoadjuvant and/or adjuvant therapy with pembrolizumab in 35 patients with recurrent, surgically resectable glioblastoma. Patients who were randomized to receive neoadjuvant pembrolizumab, with continued adjuvant therapy following surgery, had significantly extended overall survival compared to patients that were randomized to receive adjuvant, post-surgical programmed cell death protein 1 (PD-1) blockade alone. Neoadjuvant PD-1 blockade was associated with upregulation of T cell- and interferon-γ-related gene expression, but downregulation of cell-cycle-related gene expression within the tumor, which was not seen in patients that received adjuvant therapy alone. Focal induction of programmed death-ligand 1 in the tumor microenvironment, enhanced clonal expansion of T cells, decreased PD-1 expression on peripheral blood T cells and a decreasing monocytic population was observed more frequently in the neoadjuvant group than in patients treated only in the adjuvant setting. These findings suggest that the neoadjuvant administration of PD-1 blockade enhances both the local and systemic antitumor immune response and may represent a more efficacious approach to the treatment of this uniformly lethal brain tumor.

Brain metastases are an increasing global public health concern, even as survival rates improve for patients with metastatic disease. Both metastases and the sequelae of their treatment are key determinants of the inter-related priorities of patient survival, function, and quality of life, mandating a multidimensional approach to clinical care and research. At a virtual National Cancer Institute Workshop in September, 2022, key stakeholders convened to define research priorities to address the crucial areas of unmet need for patients with brain metastases to achieve meaningful advances in patient outcomes. This Policy Review outlines existing knowledge gaps, collaborative opportunities, and specific recommendations regarding consensus priorities and future directions in brain metastases research. Achieving major advances in research will require enhanced coordination between the ongoing efforts of individual organisations and consortia. Importantly, the continual and active engagement of patients and patient advocates will be necessary to ensure that the directionality of all efforts reflects what is most meaningful in the context of patient care.