A comparison of safety and efficacy of cytotoxic versus molecularly targeted drugs in pediatric phase I solid tumor oncology trials

Pediatric Tumors as Disorders of Development: The Case for In Vitro Modeling Based on Human Stem Cells

Despite improvements in patient outcomes, pediatric cancer remains a leading cause of non-accidental death in children. Recent genetic analysis of patients with pediatric cancers indicates an important role for both germline genetic predisposition and cancer-specific somatic driver mutations. Increasingly, evidence demonstrates that the developmental timepoint at which the cancer cell-of-origin transforms is critical to tumor identity and therapeutic response. Therefore, future therapeutic development would be bolstered by the use of disease models that faithfully recapitulate the genetic context, cell-of-origin, and developmental window of vulnerability in pediatric cancers. Human stem cells have the potential to incorporate all of these characteristics into a pediatric cancer model, while serving as a platform for rapid genetic and pharmacological testing. In this review, we describe how human stem cells have been used to model pediatric cancers and how these models compare to other pediatric cancer model modalities.

Lessons Learned: Utilization of a Reference Laboratory for Targeted Sequencing of Pediatric Tumors at a Single Institution

Our study aims to report the prevalence of potentially actionable oncogenic variants in a sample of pediatric tumors from a single institution using a reference laboratory for tumor profiling. We investigated genomic alterations and immunotherapy biomarkers such a tumor mutation burden, microsatellite instability, and programmed death-ligand 1. Patients treated in the Cook Children's Health Care System who had tumor profiling performed by Foundation Medicine between January 1, 2013, and May 1, 2019, were included. Demographic variables, results of tumor profiling, and subsequent use of targeted therapies were captured. Eighty-one patients were in our final data set; patients had diagnoses of central nervous system tumors (n=5), leukemia and lymphoma (n=4), neuroblastoma (n=32), and other solid tumors (n=40). One or more genomic alterations were identified in 68 (84%) of patients, 34 of which had potential targeted therapies available. In all, 44/51 patients tested for tumor mutation burden had low tumor burden, and the rest had intermediate burden. All 41 patients tested for microsatellite instability status were microsatellite stable. Six of 34 patients tested for programmed death-ligand 1 status were positive. Twelve patients received targeted therapy. This study highlights a subset of pediatric tumors harboring targetable genetic alterations and describes the use of a reference laboratory for tumor profiling.

Risk and Benefit for Targeted Therapy Agents in Pediatric Phase II Trials in Oncology: A Systematic Review with a Meta-Analysis

BACKGROUND

For research with human participants to be ethical, risk must be in a favorable balance with potential benefits. Little is known about the risk/benefit ratio for pediatric cancer phase II trials testing targeted therapies.

OBJECTIVE

Our aim was to conduct a systematic review of preliminary efficacy and safety profiles of phase II targeted therapy clinical trials in pediatric oncology.

METHODS

Our protocol was prospectively registered in PROSPERO (CRD42020146491). We searched EMBASE and PubMed for phase II pediatric cancer trials testing targeted agents. We included solid and hematological malignancy studies published between 1 January, 2015 and 27 February, 2020. We measured risk using drug-related grade 3 or higher adverse events, and benefit by response rates. When possible, data were meta-analyzed. All statistical tests were two-sided.

RESULTS

We identified 34 clinical trials (1202 patients) that met our eligibility criteria. The pooled overall response rate was 24.4% (95% confidence interval [CI] 14.5-34.2) and was lower in solid tumors, 6.4% (95% CI 3.2-9.6), compared with hematological malignancies, 55.1% (95% CI 35.9-74.3); p < 0.001. The overall fatal drug-related (grade 5) adverse event rate was 1.6% (95% CI 0.6-2.5), and the average drug-related grade 3/4 adverse event rate per person was 0.66 (95% CI 0.55-0.78).

CONCLUSIONS

We provide an estimate for the risks and benefits of participation in pediatric phase II cancer trials. These data may be used as an empirical basis for informed communication about benefits and burdens in pediatric oncology research.

Opportunities and Challenges in Drug Development for Pediatric Cancers

The use of targeted small-molecule therapeutics and immunotherapeutics has been limited to date in pediatric oncology. Recently, the number of pediatric approvals has risen, and regulatory initiatives in the United States and Europe have aimed to increase the study of novel anticancer therapies in children. Challenges of drug development in children include the rarity of individual cancer diagnoses and the high prevalence of difficult-to-drug targets, including transcription factors and epigenetic regulators. Ongoing pediatric adaptation of biomarker-driven trial designs and further exploration of agents targeting non-kinase drivers constitute high-priority objectives for future pediatric oncology drug development. SIGNIFICANCE: Increasing attention to drug development for children with cancer by regulators and pharmaceutical companies holds the promise of accelerating the availability of new therapies for children with cancer, potentially improving survival and decreasing the acute and chronic toxicities of therapy. However, unique approaches are necessary to study novel therapies in children that take into account low patient numbers, the pediatric cancer genomic landscape and tumor microenvironment, and the need for pediatric formulations. It is also critical to evaluate the potential for unique toxicities in growing hosts without affecting the pace of discovery for children with these life-threatening diseases.

Phase I trials and therapeutic intent in the age of precision oncology: What is a patient's chance of response?

The advancement of therapeutic strategies in oncology such as precision oncology has generated significant interest in better estimating the response of modern phase I cancer clinical trials. These estimates have varied widely. In this commentary, we provide an umbrella review of phase I response rates and discuss methodological reasons for variation in prior estimates which include limited use of unpublished data, the inclusion of expansion cohorts that artificially raise response rates of cumulative response rates, varying enrolment of haematologic malignancies, and increased next in class drugs.

A Systematic Review of Pediatric Phase I Trials in Oncology: Toxicity and Outcomes in the Era of Targeted Therapies

BACKGROUND

Pediatric phase I oncology trials have historically focused on safety and toxicity, with objective response rates (ORRs) <10%. Recently, with an emphasis on targeted approaches, response rates may have changed. We analyzed outcomes of recent phase I pediatric oncology trials.

MATERIALS AND METHODS

This was a systematic review of phase I pediatric oncology trials published in 2012-2017, identified through PubMed and EMBASE searches conducted on March 14, 2018. Selection criteria included full-text articles with a pediatric population, cancer diagnosis, and a dose escalation schema. Each publication was evaluated for patient characteristics, therapy type, trial design, toxicity, and response.

RESULTS

Of 3,431 citations, 109 studies (2,713 patients) met eligibility criteria. Of these, 78 (72%) trials incorporated targeted therapies. Median age at enrollment/trial was 11 years (range 3-21 years). There were 2,471 patients (91%) evaluable for toxicity, of whom 300 (12.1%) experienced dose-limiting toxicity (DLT). Of 2,143 patients evaluable for response, 327 (15.3%) demonstrated an objective response. Forty-three (39%) trials had no objective responses. Nineteen trials (17%) had an ORR >25%, of which 11 were targeted trials and 8 were combination cytotoxic trials. Targeted trials demonstrated a lower DLT rate compared with cytotoxic trials (10.6% vs. 14.7%; p = .003) with similar ORRs (15.0% vs. 15.9%; p = .58).

CONCLUSION

Pediatric oncology phase I trials in the current treatment era have an acceptable DLT rate and a pooled ORR of 15.3%. A subset of trials with target-specific enrollment or combination cytotoxic therapies showed high response rates, highlighting the importance of these strategies in early phase trials.

IMPLICATIONS FOR PRACTICE

Enrollment in phase I oncology trials is crucial for development of novel therapies. This systematic review of phase I pediatric oncology trials provides an assessment of outcomes of phase I trials in children, with a specific focus on the impact of targeted therapies. These data may aid in evaluating the landscape of current phase I options for patients and enable more informed communication regarding risk and benefit of phase I clinical trial participation. The results also suggest that, in the current treatment era, there is a rationale to increase earlier access to targeted therapy trials for this refractory patient population.

The impact of competition between cancer cells and healthy cells on optimal drug delivery

Cell competition is recognized to be instrumental to the dynamics and structure of the tumor-host interface in invasive cancers. In mild competition scenarios, the healthy tissue and cancer cells can coexist. When the competition is aggressive, competitive cells, the so called super-competitors, expand by killing other cells. Novel chemotherapy drugs and molecularly targeted drugs are commonly administered as part of cancer therapy. Both types of drugs are susceptible to various mechanisms of drug resistance, obstructing or preventing a successful outcome. In this paper, we develop a cancer growth model that accounts for the competition between cancer cells and healthy cells. The model incorporates resistance to both chemotherapy and targeted drugs. In both cases, the level of drug resistance is assumed to be a continuous variable ranging from fully-sensitive to fully-resistant. Using our model we demonstrate that when the competition is moderate, therapies using both drugs are more effective compared with single drug therapies. However, when cancer cells are highly competitive, targeted drugs become more effective. The results of the study stress the importance of adjusting the therapy to the pre-treatment resistance levels. We conclude with a study of the spatiotemporal propagation of drug resistance in a competitive setting, verifying that the same conclusions hold in the spatially heterogeneous case.

Reprioritizing Risk and Benefit: The Future of Study Design in Early-Phase Cancer Research

The scientific purpose of phase I trials is to determine the maximum tolerated dose and/or optimal biological dose of experimental agents. Yet most participants in phase I oncology trials enroll hoping for direct medical benefit. The most common phase I trial designs use low starting doses and escalate cautiously in a "risk-escalation" model focused on minimizing risk for each participant. This approach ensures that a proportion of subjects will likely not receive any benefit, even if the intervention proves to be successful at appropriate doses. In this article, we propose that trial designs should employ dosing strategies that increase chances of providing benefit if the investigational agent should prove to be successful while limiting risk to reasonable levels. We then describe how adaptive trial designs can facilitate refined dose optimization based on both therapeutic benefit and toxicity, which can simultaneously decrease the risk of harm while increasing the chances of benefit.

Ethical issues in the care of adolescent and young adult oncology patients

The diagnosis and treatment of cancer leads to short-term and long-term challenges for every patient. This is especially true for adolescents and young adults (AYAs) with cancer who strive to gain independence, autonomy, confidence, and social status while developing into adulthood. In this article, we review prominent ethical issues in AYA oncology that are related to autonomy, shared decision-making, care refusal or abandonment, end-of-life care, truth telling, and fertility preservation. Clinicians should recognize that AYA patients develop at their own pace; the onus lies with clinicians to determine the patient's interests, values, maturity, and desire to participate in decision-making.

Transcriptome based individualized therapy of refractory pediatric sarcomas: feasibility, tolerability and efficacy

Survival rates of pediatric sarcoma patients stagnated during the last two decades, especially in adolescents and young adults (AYAs). Targeted therapies offer new options in refractory cases. Gene expression profiling provides a robust method to characterize the transcriptome of each patient’s tumor and guide the choice of therapy.

Twenty patients with refractory pediatric sarcomas (age 8-35 years) were assessed with array profiling: ten had Ewing sarcoma, five osteosarcoma, and five soft tissue sarcoma. Overexpressed genes and deregulated pathways were identified as actionable targets and an individualized combination of targeted therapies was recommended. Disease status, survival, adverse events (AEs), and quality of life (QOL) were assessed in patients receiving targeted therapy (TT) and compared to patients without targeted therapy (non TT).

Actionable targets were identified in all analyzed biopsies. Targeted therapy was administered in nine patients, while eleven received no targeted therapy. No significant difference in risk factors between these two groups was detected. Overall survival (OS) and progression free survival (PFS) were significantly higher in the TT group (OS: P=0.0014, PFS: P=0.0011). Median OS was 8.83 versus 4.93 months and median PFS was 6.17 versus 1.6 months in TT versus non TT group, respectively. QOL did not differ at baseline as well as at four week intervals between the two groups. TT patients had less grade 1 AEs (P=0.009). The frequency of grade 2-4 AEs did not differ.

Overall, expression based targeted therapy is a feasible and likely beneficial approach in patients with refractory pediatric sarcomas that warrants further study.

Random-effects meta-analysis for systematic reviews of phase I clinical trials: Rare events and missing data

Phase I trials aim to establish appropriate clinical and statistical parameters to guide future clinical trials. With individual trials typically underpowered, systematic reviews and meta-analysis are desired to assess the totality of evidence. A high percentage of zero or missing outcomes often complicate such efforts. We use a systematic review of pediatric phase I oncology trials as an example and illustrate the utility of advanced Bayesian analysis. Standard random-effects methods rely on the exchangeability of individual trial effects, typically assuming that a common normal distribution sufficiently describes random variation among the trial level effects. Summary statistics of individual trial data may become undefined with zero counts, and this assumption may not be readily examined. We conduct Bayesian semi-parametric analysis with a Dirichlet process prior and examine the assumption. The Bayesian semi-parametric analysis is also useful for visually summarizing individual trial data. It provides alternative statistics that are computed free of distributional assumptions about the shape of the population of trial level effects. Outcomes are rarely entirely missing in clinical trials. We utilize available information and conduct Bayesian incomplete data analysis. The advanced Bayesian analyses, although illustrated with the specific example, are generally applicable. © 2016 The Authors. Research Synthesis Methods Published by John Wiley & Sons Ltd.