Postoperative radiotherapy timing, molecular subgroups and treatment outcomes of Thai pediatric patients with medulloblastoma.

INTRODUCTION: Medulloblastoma (MB) is the most common childhood malignant brain tumor worldwide. Recently, molecular classification was established and started to play a role in the management of MB; however, studies involving molecular defined MB in Southeast Asia have been limited. We aimed to describe, and correlate clinical characteristics and molecular subgroups with therapeutic outcomes of Thai pediatric patients with MB. MATERIALS AND METHODS: Pediatric MB patients treated at King Chulalongkorn Memorial Hospital in Thailand from 2006 to 2018 were recruited. Patients were classified by clinical characteristics into standard- and high-risk groups, which determined treatment regimen. Retrospectively, available tumor tissues were classified into 3 molecular subgroups using immunohistochemistry: 1) WNT, 2) SHH, and 3) non-WNT/non-SHH. The primary outcome was 5-year overall survival (OS). Risk factors associated with OS were analyzed using cox regression analysis. RESULTS: Fifty-three Thai pediatric patients with MB were enrolled. The median follow-up time was 60 months. The 5-year OS for all patients, and patients with standard-risk and high-risk were 74.2%, 76.3% and 71.4%, respectively. Tumor tissues of 24 patients were available, of which 23 could be molecularly classified. Two, one and 20 were in the WNT, SHH and non-WNT/non-SHH subtypes with 5-year OS of 100%, 100% and 78.9%, respectively. Using multivariate analysis, the interval of more than 8 weeks between surgery and radiotherapy was significantly correlated with a decrease in the 5-year OS. CONCLUSION: Interval between surgery and radiotherapy within 8 weeks was associated with good therapeutic outcomes among Thai pediatric patients with MB. Simplified molecular subtyping combined with clinical characteristics is practical in risk classification of patients with MB in institutes with limited resources.

KRAS Mutation in Pediatric Intracranial Germ Cell Tumors.

BACKGROUND: Intracranial germ cell tumors (IGCTs) are rare, highly curable neoplasms. KRAS is a gene in the KIT/RAS signaling pathway, and KRAS mutations have been reported in patients diagnosed with IGCTs. OBJECTIVES: To describe the clinicopathologic and molecular features of KRAS mutation and the treatment outcome of children diagnosed with IGCTs. METHODS: Patients diagnosed with IGCTs at the Department of Pediatrics, King Chulalongkorn Memorial Hospital from 2007 to 2016 were retrospectively reviewed. DNA was extracted from formalin-fixed, paraffin-embedded tissue and used for molecular study. Mutations in codons 12, 13, and 61 of the KRAS gene were detected using the cobas® KRAS mutation test and pyrosequencing. RESULTS: Eighteen patients were diagnosed with IGCTs (11 males and 7 females): nine with germinomas and nine with non-germinomatous GCTs (NGGCTs). The age range of the patients was 5-14 years (median 10.5 years). Elevated markers were revealed in approximately 25% of the patients. Four patients (two with germinomas and two with NGGCTs) had leptomeningeal involvement. All patients underwent tumor biopsy and received neoadjuvant chemotherapy. Radiotherapy was administered in 16 patients, and craniospinal radiation was administered only in patients with leptomeningeal metastasis. With a median follow-up of 26 months, overall survival was 88.9% in the patients with germinomas and 37% in the patients with NGGCTs. Mutation of the KRAS gene was detected using pyrosequencing in one patient. The mutation located at codon 61, with frequency 38.3% units, nucleotide substitution CAA > CTA, and amino acid substitution, was Q61L. The patient carrying the mutant gene was diagnosed with germinoma with cerebrospinal fluid metastasis and eventually died from treatment-related toxicity. CONCLUSION: Our study revealed the treatment outcomes of IGCTs in Thai children. The metastatic germinoma patient with KRAS codon 61 mutation had a poor outcome, supporting that Q61L has a clinical correlation with IGCTs.

Pediatric fibromyxoid tumor with PLAG1 fusion: An emerging entity with a novel intracranial location.

Translocations involving PLAG1 occur in several tumors, most commonly pleomorphic adenoma and lipoblastoma. Recently, a distinctive soft tissue tumor with a PLAG1 fusion has been reported in the pediatric age group. These are low grade tumors with a fibroblastic or mixed fibroblastic and myxoid morphology but no other lines of differentiation. They are typically immunopositive for desmin and CD34. The partner genes for these tumors have included YWHAZ, EEF1A1, ZFHX4l, CHCHD7, and PCMTD1. We report another case of this fibromyxoid tumor with a PLAG1 fusion, this time with COL3A1 as the partner gene. The fusion placed expression of a full-length PLAG1 protein under the control of the constitutively active COL3A1 promoter. Overexpression of PLAG1 was confirmed by diffusely positive immunostaining for PLAG1. The most novel aspect of this tumor is the intracranial location. Opinion has been divided over whether these tumors are a specific entity, or related to lipoblastoma, since that tumor also typically occurs in soft tissue in the pediatric age group and shows many of the same gene fusions. However, lipoblastoma has never been reported in an intracranial location and, thus, our case provides compelling evidence that this fibromyxoid tumor is indeed a distinct entity.

Germline and somatic DICER1 mutations in a pituitary blastoma causing infantile-onset Cushing's disease.

CONTEXT: Pituitary blastoma causing Cushing's syndrome in infancy is very rare, and its molecular pathomechanism is not well understood. OBJECTIVE: Our objective was to identify genetic changes of a pituitary blastoma causing infantile-onset Cushing's syndrome in a Thai girl without a family history of cancers. METHODS: Genomic DNA from both leukocytes and tumor tissues was used for whole-exome sequencing (WES) and Sanger sequencing of DICER1. The cDNA reverse-transcribed from RNA extracted from both leukocytes and tumor tissues was used for Sanger sequencing, quantitative real-time PCR (qRT-PCR), and pyrosequencing of DICER1. RESULTS: WES of leukocytes identified a novel heterozygous c.3046delA (p.S1016VfsX1065) mutation in the DICER1 gene. WES of the tumor tissues detected the same frameshift germline mutation and another novel somatic missense c.5438A→T (p.E1813V) mutation. Both mutations were validated by Sanger sequencing. Quantitative real-time PCR revealed that the DICER1 mRNA levels of the tumor tissues were 54% compared with those of her leukocytes. Pyrosequencing showed that the deletion allele constituted 12% and 0% of the DICER1 cDNA of the proband's leukocytes and tumor tissues, respectively. CONCLUSION: Our study extends the phenotypic and mutational spectrum of DICER1 mutations to include infantile-onset Cushing's disease and 2 novel mutations. Loss of function of both DICER1 alleles appears to be crucial to initiate tumor development.

Outcome of medulloblastoma in children treated with reduced-dose radiation therapy plus adjuvant chemotherapy.

Medulloblastoma is the most common malignant brain tumor in children. Post-surgical craniospinal irradiation (CSI; 30-36 Gy) plus local boost radiation therapy (RT; 54-56 Gy) is a standard treatment for children with medulloblastoma who are over 3 years old, resulting in a 5-year overall survival (OS) rate of 46% to 65% in average-risk patients and 50% in high-risk patients. The addition of chemotherapy has the benefit of reducing complications from radiation and improving the OS rate. Using this approach, the estimated 5-year OS rates for patients with average- and high-risk medulloblastomas treated with different protocols are 65% to 85% and 16% to 70%, respectively. In this study, we determined the outcome of patients with average- and high-risk medulloblastomas treated with reduced dosage CSI and chemotherapy with an oral etoposide-based regimen. The study included 49 patients, with a mean age of 7.7 ± 3.4 years. Twenty-six patients (53%) were classified as average-risk and 23 patients (47%) as high-risk. In the average-risk group, the 5-year progression free survival (PFS) rate was 62.9% ± 10% and the 5-year OS rate was 70.4% ± 9.5%. In the high-risk group the 5-year PFS rate was 48.9% ± 13% and the 5-year OS rate was 49.7% ± 13%. In the average-risk group, patients who received CSI of either 24 Gy (n=20) or 36 Gy (n=9) showed no difference in their 5-year PFS and OS rates. We found that patients who were ≤ 10 years old and patients who were female had a significantly better 5-year PFS rate.