Cancer predisposition in pediatric neuro-oncology-practical approaches and ethical considerations

Immunotherapy for pediatric low-grade gliomas

Pediatric low-grade gliomas (pLGGs) are the most common brain tumor types affecting children. Although gross-total resection remains the treatment of choice, many tumors are not amenable to complete removal, because they either involve midline structures, such as the optic chiasm or hypothalamus, and are not conducive to aggressive resection, or have diffuse biological features and blend with the surrounding brain. Historically, radiation therapy was used as the second-line option for disease control, but with the recognition that this often led to adverse long-term sequelae, particularly in young children, conventional chemotherapy assumed a greater role in initial therapy for unresectable tumors. A variety of agents demonstrated activity, but long-term disease control was suboptimal, with more than 50% of tumors exhibiting disease progression within 5 years. More recently, it has been recognized that a high percentage of these tumors in children exhibit constitutive activation of the mitogen-activated protein kinase (MAPK) pathway because of BRAF translocations or mutations, NFI mutations, or a host of other anomalies that converged on MAPK. This led to phase 1, 2, and 3 trials that explored the activity of blocking this signaling pathway, and the efficacy of this approach compared to conventional chemotherapy. Despite initial promise of these strategies, not all children tolerate this therapy, and many tumors resume growth once MAPK inhibition is stopped, raising concern that long-term and potentially life-long treatment will be required to maintain tumor control, even among responders. This observation has led to interest in other treatments, such as immunotherapy, that may delay or avoid the need for additional treatments. This chapter will summarize the place of immunotherapy in the current armamentarium for these tumors and discuss prior results and future options to improve disease control, with a focus on our prior efforts and experience in this field.

Genomic Newborn Screening for Pediatric Cancer Predisposition Syndromes: A Holistic Approach

As next-generation sequencing (NGS) has become more widely used, germline and rare genetic variations responsible for inherited illnesses, including cancer predisposition syndromes (CPSs) that account for up to 10% of childhood malignancies, have been found. The CPSs are a group of germline genetic disorders that have been identified as risk factors for pediatric cancer development. Excluding a few "classic" CPSs, there is no agreement regarding when and how to conduct germline genetic diagnostic studies in children with cancer due to the constant evolution of knowledge in NGS technologies. Various clinical screening tools have been suggested to aid in the identification of individuals who are at greater risk, using diverse strategies and with varied outcomes. We present here an overview of the primary clinical and molecular characteristics of various CPSs and summarize the existing clinical genomics data on the prevalence of CPSs in pediatric cancer patients. Additionally, we discuss several ethical issues, challenges, limitations, cost-effectiveness, and integration of genomic newborn screening for CPSs into a healthcare system. Furthermore, we assess the effectiveness of commonly utilized decision-support tools in identifying patients who may benefit from genetic counseling and/or direct genetic testing. This investigation highlights a tailored and systematic approach utilizing medical newborn screening tools such as the genome sequencing of high-risk newborns for CPSs, which could be a practical and cost-effective strategy in pediatric cancer care.

Current practice of cancer predisposition testing in pediatric patients with CNS tumors in the United States

An estimated 8.6% of all pediatric patients with central nervous system tumors (CNSTs) have underlying hereditary cancer predisposition (HCP). Identifying HCP affects risk assessment and medical management options for the patients and their family members. However, there is a lack of consensus on the optimal germline genetic testing (GT) approach for pediatric patients with CNSTs. As a first step in addressing the need for consensus, we surveyed oncology and genetics providers from 47 institutions in professional organizations across the United States. We investigated their current practice (e.g., GT decisions and ordering practices) when assessing pediatric patients with CNSTs for HCP. We received 60 responses from 21 pediatric oncologists, 10 neuro-oncologists, 28 genetics providers, and one neuro-oncologist/geneticist. Results demonstrate genetic counselors, followed by oncologists, most often facilitated consent, ordered testing, and selected which test to order. The most ordered test was a multi-gene panel (60%). Of 18 CNST diagnoses, choroid plexus carcinoma (CPC) was the diagnosis for which most providers (78%) reported they would offer GT. For medulloblastoma, 56% overall reported they would offer GT (64% of genetics providers, 62% of neuro-oncologists, 20% of pediatric oncologists; p = .050). Findings suggest that even for the CNSTs most commonly known to be associated with HCP regardless of family history, there was variability in providers' decisions to offer GT. The lack of consensus in GT decisions in our study indicates inconsistencies in the genetics care of pediatric patients with CNSTs, demonstrating a need for consensus guidelines to promote consistent genetics care.

Heritable cancer predisposition testing in pediatric cancer patients excluding retinoblastoma in a middle-income country

Resource-limited settings often have financial barriers to genetic testing for heritable cancer. This retrospective study investigated the pattern of heritable cancer predisposition testing in a middle-income country over the period 2014-2021, excluding retinoblastoma. After establishing a specific fund in 2019, rate of tests increased from 1.1% to 10.9% of new diagnoses. Most common testing was for constitutional mismatch repair deficiency (CMMRD), rhabdoid predisposition syndrome, TP53 (tumor protein 53) mutation, and hereditary cancer panel. Of 33 patients, 13 (39%) tested positive, 12 (36%) negative, and eight (24%) had variants of unknown significance. Positivity rate was 43% for a clinical phenotype and 44% for a tumor type indication.