Radiographic Response Assessment Strategies for Early-Phase Brain Trials in Complex Tumor Types and Drug Combinations: from Digital "Flipbooks" to Control Systems Theory.

There is an urgent need for drug development in brain tumors. While current radiographic response assessment provides instructions for identifying large treatment effects in simple high- and low-grade gliomas, there remains a void of strategies to evaluate complex or difficult to measure tumors or tumors of mixed grade with enhancing and non-enhancing components. Furthermore, most patients exhibit some period of alteration in tumor growth after starting a new therapy, but simple response categorization (e.g., stable disease, progressive disease) fails to provide any meaningful insight into the depth or degree of potential "subclinical" therapeutic response. We propose a creative solution to these issues based on a tiered strategy meant to increase confidence in identifying therapeutic effects even in the most challenging tumor types, while also providing a framework for complex evaluation of combination and sequential treatment schemes. Specifically, we demonstrate the utility of digital "flipbooks" to quickly identify subtle changes in complex tumors. We show how a modified Levin criteria can be used to quantify the degree of visual changes, while establishing estimates of the association between tumor volume and visual inspection. Lastly, we introduce the concept of quantifying therapeutic response using control systems theory. We propose measuring changes in volume (proportional), the area under the volume vs. time curve (integral) and changes in growth rates (derivative) to utilize a "PID" controller model of single or combination therapeutic activity.

Effect of eflornithine on mutation frequency in temozolomide-treated U87MG cells.

Treatment of infiltrative glioma presents a number of unique challenges due to poor penetration of typical chemotherapeutic agents into the infiltrating edge of tumors. The current chemotherapy options include nitrosoureas (e.g., lomustine) and the imidazotetrazine-class monofunctional DNA alkylating agent, temozolomide (TMZ). Both classes of drugs alkylate DNA and have relatively unrestricted passage from blood into brain where infiltrative tumor cells reside. Recent research indicates that secondary mutations detected in the RB and AKT-mTOR signaling pathways are linked to characteristics of recurrent tumors specific to TMZ-treated patients. It has been hypothesized that a decrease in rate of secondary mutations may result in delay of tumor recurrence. To that end, this study was designed to test viability of decreasing secondary mutations by disrupting the cell division cycle using eflornithine, a specific inhibitor of ornithine decarboxylase. U87MG glioblastoma cell line characterized by chromosomal abnormalities commonly attributed to primary cancers was used as a model for this study. The cells were subjected to TMZ treatment for 3 days followed by eflornithine (DFMO) treatment for 4 or 11 days. It was shown that TMZ significantly increased the frequency of mutations in U87MG glioblastoma cells while DFMO-treated cells showed mutation frequency statistically similar to that of the untreated cells on the respective treatment days. The findings of this study provide evidence to support the hypothesis that DFMO may inhibit progression of DNA mutations caused by alkylating chemotherapy agents, such as TMZ.

Phase I/II study of sorafenib in combination with erlotinib for recurrent glioblastoma as part of a 3-arm sequential accrual clinical trial: NABTC 05-02.

BACKGROUND: Receptor tyrosine kinases such as epidermal growth factor receptors (EGFRs) and their downstream signaling pathways such as the Ras-Raf-mitogen-activated protein kinase (MAPK) pathway play important roles in glioblastoma (GBM). This study investigated the safety, pharmacokinetics, and efficacy of sorafenib (Ras/Raf/MAPK inhibitor) in combination with erlotinib (EGFR inhibitor) for treatment of recurrent GBMs. METHODS: Patients with recurrent GBM were eligible. A novel sequential accrual trial design was used, where patients were sequentially accrued into separate treatment arms in phase I and phase II investigations to optimize recruitment efficiency. In phase I, a standard 3 + 3 format was used to identify dose-limiting toxicities (DLTs), determine maximum tolerated dose (MTD), and investigate pharmacokinetics. Phase II followed a 2-stage design with the primary endpoint being 6-month progression-free survival (PFS6). RESULTS: Sixteen patients were recruited for phase I, and the MTD was determined to be sorafenib 200 mg twice daily and erlotinib 100 mg once daily. DLTs include Grade 3 hypertension, Grade 3 elevated liver transaminases, and Grade 4 elevated lipase. While erlotinib did not affect sorafenib levels, sorafenib reduced erlotinib levels. In phase II, 3 of 19 stage 1 participants were progression free at 6 months. This did not meet the predetermined efficacy endpoint, and the trial was terminated. CONCLUSION: This study identified the MTD and DLTs for sorafenib and erlotinib combination therapy for recurrent GBMs; however, efficacy data did not meet the primary endpoint. This study also demonstrates the feasibility of a novel sequential accrual clinical trial design that optimizes patient recruitment for multiarm studies, which is particularly effective for multicenter clinical trials.

Understanding brain penetrance of anticancer drugs.

This paper explicates the impact of tumor capillary permeability for glioma World Health Organization (WHO) grades II to IV on brain-penetrant drug entry and distribution within the tumor and the brain adjacent to tumor (leading edge). In addition, we consider the distribution of non-brain penetrant drugs and how, in some cases, large-molecular-weight drugs might achieve good distribution into tumor and brain adjacent to tumor.

Clinical importance of eflornithine (α-difluoromethylornithine) for the treatment of malignant gliomas.

This review covers the literature between 1989 and 2007 on studies relevant to the neuro-oncology usage of eflornithine (α-difluoromethylornithine), an oral agent that irreversibly inhibits the enzyme ornithine decarboxylase. It covers the use of eflornithine, alone or in combination, to treat high-grade gliomas. In addition, we provide an update on overall survival from The University of Texas MD Anderson Cancer Center Community Clinical Oncology Program and Clinical Trials Data Office that demonstrates a meaningful benefit in overall survival for eflornithine as a single agent and in combination with nitrosourea-based therapies for anaplastic gliomas. We also provide a framework for understanding the basis and study design of the ongoing pivotal, registrational Phase III multicenter trial for recurrent/progressive anaplastic astrocytoma.

Phase I study of sorafenib and tipifarnib for recurrent glioblastoma: NABTC 05-02.

Recurrent glioblastoma (GBM) has a very low 6-month progression free survival (PFS) with currently available treatments. Combination chemotherapy to target multiple cell signaling pathways is currently being investigated in order to improve prognosis for recurrent disease. The purpose of this phase I study was to determine the maximum tolerated dose (MTD) for the combination of tipifarnib and sorafenib for the treatment of recurrent GBM. Patients with pathologically proven WHO grade IV GBM and radiographically proven tumor recurrence were eligible for this study. Treatments included sorafenib at twice daily and escalating dosages of tipifarnib. Dose-limiting toxicity (DLT) was determined over the first 28-days of treatments, and the MTD was determined in a 3 + 3 study design. We enrolled 24 patients, and 21 patients completed the MTD period. The study was stopped early with no MTD determination for excessive toxicities. The last dose level reached was sorafenib at 200 mg twice a day and tipifarnib 100 mg twice a day on an alternating week schedule. The DLTs included diarrhea, lipase elevation, hypophosphatemia, and arthralgia. The combination of sorafenib and tipifarnib has excessive toxicities and full single agent dosages could not be achieved in combination.

CNS Anticancer Drug Discovery and Development: 2016 conference insights.

CNS Anticancer Drug Discovery and Development, 16-17 November 2016, Scottsdale, AZ, USA The 2016 second CNS Anticancer Drug Discovery and Development Conference addressed diverse viewpoints about why new drug discovery/development focused on CNS cancers has been sorely lacking. Despite more than 70,000 individuals in the USA being diagnosed with a primary brain malignancy and 151,669-286,486 suffering from metastatic CNS cancer, in 1999, temozolomide was the last drug approved by the US FDA as an anticancer agent for high-grade gliomas. Among the topics discussed were economic factors and pharmaceutical risk assessments, regulatory constraints and perceptions and the need for improved imaging surrogates of drug activity. Included were modeling tumor growth and drug effects in a medical environment in which direct tumor sampling for biological effects can be problematic, potential new drugs under investigation and targets for drug discovery and development. The long trajectory and diverse impediments to novel drug discovery, and expectation that more than one drug will be needed to adequately inhibit critical intracellular tumor pathways were viewed as major disincentives for most pharmaceutical/biotechnology companies. While there were a few unanimities, one consensus is the need for continued and focused discussion among academic and industry scientists and clinicians to address tumor targets, new drug chemistry, and more time- and cost-efficient clinical trials based on surrogate end points.

Effect of angiotensin system inhibitors on survival in newly diagnosed glioma patients and recurrent glioblastoma patients receiving chemotherapy and/or bevacizumab.

Given prior studies that suggest the use of angiotensin system inhibitors (ASIs) is associated with prolonged overall survival (OS) in glioblastoma (GBM) patients, we evaluated the effect of ASIs in glioma patients receiving chemotherapy and/or bevacizumab (BEV). Using retrospective IRB-approved electronic chart review of newly diagnosed WHO grade 2-4 glioma patients from the Kaiser Permanente Tumor Registry of Northern California, we evaluated the impact of ASIs on OS by Cox proportional hazard model analysis for subgroups who received cytotoxic therapy, cytotoxic therapy with BEV, or BEV alone, as well as those with recurrent GBM (rGBM). Of the 1186 glioma patients who received chemotherapy ASI exposure improved OS (HR 0.82; 95% CI 0.71, 0.93; p = 0.003). When stratified by BEV exposure, a sub-analysis revealed further OS advantage for the BEV group (HR 0.75, 95% CI 0.62, 0.90; p = 0.002). In a second cohort of 181 rGBM patients who received BEV in varying dosages, ASI exposure conferred an OS advantage (HR 0.649; 95% CI 0.46, 0.92; p = 0.016). Moreover, patients with ASI exposure who received low-dose BEV treatment (AUCBEV < 3.6 mg wk/kg) had a significantly longer OS (median = 99 weeks; 95% CI 44.3, 205) than those without ASI (median OS = 55.6 weeks; 95% CI 37.7-73.7; p = 0.032). ASI use is associated with longer OS in glioma patients. Further survival advantage with ASI use was observed in rGBM patients receiving low-dose bevacizumab. These data warrant prospective evaluation of adding ASI to low-dose BEV treatment in GBM patients to improve the outcome of standard therapies.

CNS Anticancer Drug Discovery and Development Conference White Paper.

Following the first CNS Anticancer Drug Discovery and Development Conference, the speakers from the first 4 sessions and organizers of the conference created this White Paper hoping to stimulate more and better CNS anticancer drug discovery and development. The first part of the White Paper reviews, comments, and, in some cases, expands on the 4 session areas critical to new drug development: pharmacological challenges, recent drug approaches, drug targets and discovery, and clinical paths. Following this concise review of the science and clinical aspects of new CNS anticancer drug discovery and development, we discuss, under the rubric "Accelerating Drug Discovery and Development for Brain Tumors," further reasons why the pharmaceutical industry and academia have failed to develop new anticancer drugs for CNS malignancies and what it will take to change the current status quo and develop the drugs so desperately needed by our patients with malignant CNS tumors. While this White Paper is not a formal roadmap to that end, it should be an educational guide to clinicians and scientists to help move a stagnant field forward.

Impact of bevacizumab administered dose on overall survival of patients with progressive glioblastoma.

Bevacizumab (BEV, Avastin(®)) produces durable objective radiological responses of 20-26 %, median response durations of 16-18 weeks, and median overall survival (mOS) of 31-40 weeks. While the use of BEV is well-established, the lack of dose-response studies in glioblastoma (GBM) patients raises the question whether current dosing practice is optimal. As a result of differing approaches to BEV dosing that ranged from the FDA approved package insert dose of 10 mg/kg every 2 weeks to 7.5 mg/kg every 3-4 weeks, among physicians within Northern California Kaiser Permanente hospitals over 4+ years, we did an IRB-approved retrospective analysis of patients seen in Northern California Kaiser Permanente facilities and treated with BEV. Between September 1, 2008 and August 31, 2013, 181 patients received BEV for tumor progression/recurrence starting 2.6 weeks after completion of chemoradiation. The integrated BEV administered dose-week (AUCBEV) for all patients had a median AUCBEV of 3.6 mg·wk/kg). Maximum likelihood analysis found patients over 65 years did worse than younger patients (p = 0.004), women lived longer (p = 0.002), and patients treated below the AUCBEV did better than those treated above the median AUCBEV (p = 0.003). mOS for BEV starting 1 month after chemoradiation was 45 versus 68 weeks (p = 0.012) and BEV starting 3 months after chemoradiation was 40 versus 74 weeks (p = 0.0085). Dosing BEV at half the standard dose for progressive/recurrent GBM was at least equivalent to or, maybe better than standard dosing. Unexplained was the observation that females had longer OS with BEV than males.

Randomized phase II adjuvant factorial study of dose-dense temozolomide alone and in combination with isotretinoin, celecoxib, and/or thalidomide for glioblastoma.

BACKGROUND: Chemoradiation, followed by adjuvant temozolomide, is the standard treatment for newly diagnosed glioblastoma. Adding other active agents may enhance treatment efficacy. METHODS: The primary objective of this factorial phase II study was to determine if one of 3 potential chemotherapy agents added to dose-dense temozolomide (ddTMZ) improves progression-free survival (PFS) for patients with newly diagnosed glioblastoma. A prior phase I trial established the safety of combining ddTMZ with isotretinoin, celecoxib, and/or thalidomide. Adults with good performance status and no evidence of progression post chemoradiation were randomized into 8 arms: ddTMZ alone (7 days on/7 days off) or doublet, triplet, and quadruplet combinations with isotretinoin, celecoxib, and thalidomide. RESULTS: The study enrolled 155 participants with a median age of 53 years (range, 18-84 y). None of the agents demonstrated improved PFS when compared with arms not containing that specific agent. There was no difference in PFS for triplet compared with doublet regimens, although a trend for improved overall survival (OS) was seen (20.1 vs 17.0 months, P = .15). Compared with ddTMZ, the ddTMZ + isotretinoin doublet had worse PFS (10.5 vs 6.5 months, P = .043) and OS (21.2 vs 11.7 months, P = .037). Trends were also seen for worse outcomes with isotretinoin-containing regimens, but there was no impact with celecoxib or thalidomide combinations. Treatment was well tolerated with expected high rates of lymphopenia. CONCLUSIONS: The results do not establish a benefit for these combinations but indicate that adding isotretinoin to ddTMZ may be detrimental. This study demonstrated the feasibility and utility of the factorial design in efficiently testing drug combinations in newly diagnosed glioblastoma. CLINICALTRIALSGOV IDENTIFIER: NCT00112502.

Getting more out of survival data by using the hazard function.

Information about the survival experience for a group of patients is almost exclusively conveyed using plots of the survival function. However, the hazard function provides information about the survival experience that is not readily evident from inspection of the survival function. The hazard function tracks the instantaneous failure rate over time among the surviving patients and can be readily estimated with available software. We illustrate how these estimates can be used in conjunction with estimates of the survival function to glean clinically relevant information from survival data.

Phase I/II study of sorafenib in combination with temsirolimus for recurrent glioblastoma or gliosarcoma: North American Brain Tumor Consortium study 05-02.

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-ß, 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.

Protein and phosphoprotein levels in glioma and adenocarcinoma cell lines grown in normoxia and hypoxia in monolayer and three-dimensional cultures.

BACKGROUND: Three dimensional (3D) growths of cancer cells in vitro are more reflective of in situ cancer cell growth than growth in monolayer (2D). The present study is designed to determine changes in protein and phosphoprotein that reflect adaptation of tumor cells to 3D as compared to 2D. Since relative hypoxia is a common feature of most solid tumors, the present study also aims to look at the impact of transition from normoxia to hypoxia in these two growth conditions. RESULTS: Using reverse-phase protein arrays, we compared levels of 121 different phosphorylated and non-phosphorylated proteins in 5 glioma and 6 adenocarcinoma lines under conditions of 3D and monolayer culture in normoxia and hypoxia. A three-way analysis of variance showed levels of 82 antibodies differed between media (2D vs. 3D) and 49 differed between treatments (hypoxia vs. normoxia). Comparing 2D to 3D growth, 7 proteins were commonly (i.e., > 50% of tumors) elevated in 3D: FAK, AKT, Src, GSK3αß, TSC2, p38, and NFκßp65. Conversely, 7 other proteins are commonly decreased: ATRIP, ATR, ß-catenin, BCL-X, cyclin B1, Egr-1, and HIF-1α. Comparing normoxia to hypoxia, only NCKIPSD was commonly elevated in hypoxia; 6 proteins were decreased: cyclin B1, 4EBP1(Ser65), c-Myc, SMAD3(Ser423), S6(Ser235), and S6(Ser240). Hypoxia affected glioma cell lines differently from adenocarcinoma cell lines: 8 proteins were increased in gliomas (BAX, caspase 7, HIF-1α, c-JUN, MEK1, PARP 1 cleaved, Src, and VEGFR2) and none in adenocarcinomas. CONCLUSIONS: We identified subsets of proteins with clearly concordant/discordant behavior between gliomas and adenocarcinomas. In general, monolayer to 3D culture differences are clearer than normoxia to hypoxia differences, with anti-apoptotic, cytoskeletal rearrangement and cell survival pathways emphasized in the former and mTOR pathway, transcription, cell-cycle arrest modulation, and increased cell motility in the latter.

Phase 2 trial of irinotecan and thalidomide in adults with recurrent anaplastic glioma.

BACKGROUND: Therapeutic options for patients with anaplastic gliomas (AGs) are limited despite better insights into glioma biology. The authors previously reported improved outcome in patients with recurrent glioblastoma treated with thalidomide and irinotecan compared with historical controls. Here, results of the AG arm of the study are reported, using this drug combination. METHODS: Adults with recurrent AG previously treated with radiation therapy, with Karnofsky performance score ≥70, adequate organ function and not on enzyme-inducing anticonvulsants were enrolled. Treatment was in 6-week cycles with irinotecan at 125 mg/m(2) weekly for 4 weeks followed by 2 weeks off, and thalidomide at 100 mg daily increased to 400 mg/day as tolerated. The primary endpoint was progression-free survival rate at 6 months (PFS-6), and the secondary endpoints were overall survival (OS) and response rate (RR). RESULTS: In 39 eligible patients, PFS-6 for the intent-to-treat population was 36% (95% confidence interval [CI] = 21%, 53%), median PFS was 13 weeks (95% CI = 6%, 28%) and RR was 10%(95% CI = 3%, 24%). Radiological findings included 2 complete and 2 partial responses and 17 stable disease. Median OS from study registration was 62 weeks, (95% CI = 51, 144). Treatment-related toxicities (grade 3 or higher) included neutropenia, diarrhea, nausea, and fatigue; 6 patients experienced venous thromboembolism. Four deaths were attributable to treatment-related toxicities: 1 from pulmonary embolism, 2 from colitis, and 1 from urosepsis. CONCLUSIONS: The combination of thalidomide and irinotecan did not achieve sufficient efficacy to warrant further investigation against AG, although a subset of patients experienced prolonged PFS/OS. A trial of the more potent thalidomide analogue, lenalidomide, in combination with irinotecan against AG is currently ongoing.