Challenges in DICER1-Associated Lung Disease.

Pleuropulmonary blastoma (PPB) is a tumor occurring almost exclusively in infants and young children. This is the most common primary-lung malignancy in childhood. There is age-associated progression through a distinctive sequence of pathologic changes, from a purely multicystic lesion type I to a high-grade sarcoma type II and III. While complete resection is the cornerstone treatment for type I PPB, aggressive chemotherapy with a less favorable prognosis is associated with type II and III. DICER1 germline mutation is positive in 70% of children with PPB. Diagnosis is challenging, as it resembles congenital pulmonary airway malformation (CPAM) in imaging. Although PPB is an extremely rare malignancy, over the past five years we have encountered several children diagnosed with PPB in our medical center. Herein, we present some of these children and discuss diagnostic, ethical, and therapeutic challenges.

Genomic predictors of response to PD-1 inhibition in children with germline DNA replication repair deficiency.

Cancers arising from germline DNA mismatch repair deficiency or polymerase proofreading deficiency (MMRD and PPD) in children harbour the highest mutational and microsatellite insertion-deletion (MS-indel) burden in humans. MMRD and PPD cancers are commonly lethal due to the inherent resistance to chemo-irradiation. Although immune checkpoint inhibitors (ICIs) have failed to benefit children in previous studies, we hypothesized that hypermutation caused by MMRD and PPD will improve outcomes following ICI treatment in these patients. Using an international consortium registry study, we report on the ICI treatment of 45 progressive or recurrent tumors from 38 patients. Durable objective responses were observed in most patients, culminating in a 3 year survival of 41.4%. High mutation burden predicted response for ultra-hypermutant cancers (>100 mutations per Mb) enriched for combined MMRD + PPD, while MS-indels predicted response in MMRD tumors with lower mutation burden (10-100 mutations per Mb). Furthermore, both mechanisms were associated with increased immune infiltration even in 'immunologically cold' tumors such as gliomas, contributing to the favorable response. Pseudo-progression (flare) was common and was associated with immune activation in the tumor microenvironment and systemically. Furthermore, patients with flare who continued ICI treatment achieved durable responses. This study demonstrates improved survival for patients with tumors not previously known to respond to ICI treatment, including central nervous system and synchronous cancers, and identifies the dual roles of mutation burden and MS-indels in predicting sustained response to immunotherapy.

Cancers from Novel Pole-Mutant Mouse Models Provide Insights into Polymerase-Mediated Hypermutagenesis and Immune Checkpoint Blockade.

POLE mutations are a major cause of hypermutant cancers, yet questions remain regarding mechanisms of tumorigenesis, genotype-phenotype correlation, and therapeutic considerations. In this study, we establish mouse models harboring cancer-associated POLE mutations P286R and S459F, which cause rapid albeit distinct time to cancer initiation in vivo, independent of their exonuclease activity. Mouse and human correlates enabled novel stratification of POLE mutations into three groups based on clinical phenotype and mutagenicity. Cancers driven by these mutations displayed striking resemblance to the human ultrahypermutation and specific signatures. Furthermore, Pole-driven cancers exhibited a continuous and stochastic mutagenesis mechanism, resulting in intertumoral and intratumoral heterogeneity. Checkpoint blockade did not prevent Pole lymphomas, but rather likely promoted lymphomagenesis as observed in humans. These observations provide insights into the carcinogenesis of POLE-driven tumors and valuable information for genetic counseling, surveillance, and immunotherapy for patients. SIGNIFICANCE: Two mouse models of polymerase exonuclease deficiency shed light on mechanisms of mutation accumulation and considerations for immunotherapy.See related commentary by Wisdom and Kirsch p. 5459.

Functional Repair Assay for the Diagnosis of Constitutional Mismatch Repair Deficiency From Non-Neoplastic Tissue.

PURPOSE: Constitutional mismatch repair deficiency (CMMRD) is a highly penetrant cancer predisposition syndrome caused by biallelic mutations in mismatch repair (MMR) genes. As several cancer syndromes are clinically similar, accurate diagnosis is critical to cancer screening and treatment. As genetic diagnosis is confounded by 15 or more pseudogenes and variants of uncertain significance, a robust diagnostic assay is urgently needed. We sought to determine whether an assay that directly measures MMR activity could accurately diagnose CMMRD. PATIENTS AND METHODS: In vitro MMR activity was quantified using a 3'-nicked G-T mismatched DNA substrate, which requires MSH2-MSH6 and MLH1-PMS2 for repair. We quantified MMR activity from 20 Epstein-Barr virus-transformed lymphoblastoid cell lines from patients with confirmed CMMRD. We also tested 20 lymphoblastoid cell lines from patients who were suspected for CMMRD. We also characterized MMR activity from patients with neurofibromatosis type 1, Li-Fraumeni syndrome, polymerase proofreading-associated cancer syndrome, and Lynch syndrome. RESULTS: All CMMRD cell lines had low MMR activity (n = 20; mean, 4.14 ± 1.56%) relative to controls (n = 6; mean, 44.00 ± 8.65%; P < .001). Repair was restored by complementation with the missing protein, which confirmed MMR deficiency. All cases of patients with suspected CMMRD were accurately diagnosed. Individuals with Lynch syndrome (n = 28), neurofibromatosis type 1 (n = 5), Li-Fraumeni syndrome (n = 5), and polymerase proofreading-associated cancer syndrome (n = 3) had MMR activity that was comparable to controls. To accelerate testing, we measured MMR activity directly from fresh lymphocytes, which yielded results in 8 days. CONCLUSION: On the basis of the current data set, the in vitro G-T repair assay was able to diagnose CMMRD with 100% specificity and sensitivity. Rapid diagnosis before surgery in non-neoplastic tissues could speed proper therapeutic management.

Factors Influencing Do-Not-Resuscitate Status in Children During Last Month of Life: Single Institution Experience.

BACKGROUND: It is currently expected that about 20% of children with cancer will ultimately die. Writing advanced life directives sufficiently long before the actual death of a child ensues allows both parents and medical staff to develop optimal treatment plans in the best interests of the child. AIM OF THE STUDY: The aim of the study was to evaluate factors that may influence the process of decision-making regarding Do-Not-Resuscitate (DNR) status. METHODS: Retrospective single institution study. RESULTS: Totally, 79 patients died between September 01, 2011 and August 31, 2017. Median age of the children was 10.5 years (range, 1 to 24 y). Forty-five were males. There were 37 Muslims, 27 Jews, 9 Druze, and 6 Christians. Twenty-one patients had sarcomas, 20 had CNS tumors, 10 had neuroblastoma, 17 had leukemias/lymphomas, 11 had carcinomas, and other rare tumors as well as nonmalignant diseases. No statistically significant association between all evaluated factors and DNR order status was found. CONCLUSIONS: It is possible that, other than demographic, clinical-associated, or therapy-associated factors play an important role in the process of decision-making regarding DNR. We feel that sincere communication between parents, their child (when appropriate) and medical and psychosocial staff may have a more crucial role when such decisions have to be made.

Precision Medicine in Relapsed and Refractory Childhood Cancers: Single-center Experience, Literature Review, and Meta-analysis.

OBJECTIVE: To date, the understanding of pediatric tumor genomics and how these genetic aberrations correlate with clinical outcome is lacking. Here, we report our experience with the next-generation sequencing (NGS) test program and discuss implications for the inclusion of molecular profiling into clinical pediatric oncology trials. We also aimed to explore studies on NGS in pediatric cancers and to quantify the variability of finding actionable mutations and the clinical implications. METHODS: We present a retrospective case series of all patients whose tumor tissue underwent NGS tests during treatment in our department. We also reviewed the literature and carried out a meta-analysis to explore studies on NGS in pediatric cancers. RESULTS: In 35/37 (94%) patients, we found at least one genomic alteration (GA); mean number of GAs per patient was 2 (range, 0-67), while 164 GAs were detected. Only 3 (8%) patients received precision medicine due to their GAs for a mean of 9 months (range, 5-14 months). Four studies were included in the meta-analysis. The pooled positive actionable mutation rate was 52% (95% CI 39%-66%), and the pooled rate of children who received precision medicine was 10% (95% CI 3%-20%). CONCLUSIONS: In children and young adults with high-risk, recurrent, or refractory malignancies, tumor profiling results have clinical implications, despite barriers to the use of matched precision therapy.

Seeking a second opinion in pediatric oncology.

OBJECTIVES: The goal of this study was to identify second opinion consultations by physicians and to determine patient and family factors that appeared to contribute to a second opinion being sought. METHODS: One hundred and fifty consecutive parents of children with cancer recently treated in our Department of Pediatric Hematology Oncology were interviewed by telephone. The questionnaire included epidemiological data, details about the disease, timing of the second opinion consultation, reasons for seeking a second opinion, and the outcome of the consultation. RESULTS: Thirty-seven (24.7%) parents sought a second opinion. Advice was sought from other physicians in the hospital or at other clinics. There was a correlation to a higher socioeconomic status (P = .003) and to the number of educational years (P = .001). Most of the parents sought a second opinion because they wanted confirmation about the treatment protocol and the professional level of the hematologist oncologist/surgeon and the institution. CONCLUSIONS: Second opinion consultations were not uncommon and were mainly secondary to the desire for reassurance. Pediatric oncologists should ensure that patients and their families feel comfortable requesting a second opinion consultation.

Metastatic rhabdoid meningioma with BRAF V600E mutation and good response to personalized therapy: case report and review of the literature.

Rhabdoid meningioma is an aggressive phenotype of meningioma, associated with a poor prognosis. We present a very rare case of high-grade meningioma with rhabdoid features that eventually expressed in a coma state. Comprehensive genomic profiling using a Next Generation Sequencing (NGS) assay revealed three genomic alterations: activating BRAF mutation (V600E), loss of CDKN2A/2B, and APC I1307K. After treatment with BRAF inhibitor (dabrafenib), the child's clinical condition improved progressively. After seven months, an MEK inhibitor was added (trametinib).