Convergent evolution and multi-wave clonal invasion in H3 K27-altered diffuse midline gliomas treated with a PDGFR inhibitor.

The majority of diffuse midline gliomas, H3 K27-altered (DMG-H3 K27-a), are infiltrating pediatric brain tumors that arise in the pons with no effective treatment. To understand how clonal evolution contributes to the tumor's invasive spread, we performed exome sequencing and SNP array profiling on 49 multi-region autopsy samples from 11 patients with pontine DMG-H3 K27-a enrolled in a phase I clinical trial of PDGFR inhibitor crenolanib. For each patient, a phylogenetic tree was constructed by testing multiple possible clonal evolution models to select the one consistent with somatic mutations and copy number variations across all tumor regions. The tree was then used to deconvolute subclonal composition and prevalence at each tumor region to study convergent evolution and invasion patterns. Somatic variants in the PI3K pathway, a late event, are enriched in our cohort, affecting 70% of patients. Convergent evolution of PI3K at distinct phylogenetic branches was detected in 40% of the patients. 24 (~ 50%) of tumor regions were occupied by subclones of mixed lineages with varying molecular ages, indicating multiple waves of invasion across the pons and extrapontine. Subclones harboring a PDGFRA amplicon, including one that amplified a PDGRFAY849C mutant allele, were detected in four patients; their presence in extrapontine tumor and normal brain samples imply their involvement in extrapontine invasion. Our study expands the current knowledge on tumor invasion patterns in DMG-H3 K27-a, which may inform the design of future clinical trials.

Long-term follow-up of dose-adapted and reduced-field radiotherapy with or without chemotherapy for central nervous system germinoma.

PURPOSE: To update our institutional experience with neoadjuvant chemotherapy and minimized radiotherapy vs. radiation monotherapy for intracranial germinoma. METHODS AND MATERIALS: We retrospectively reviewed records of 59 patients with diagnosis of primary intracranial germinoma between 1977 and 2007. Treatment was irradiation alone or neoadjuvant platinum-based chemotherapy and local irradiation (initial tumor plus margin) for patients with localized complete response and reduced-dose craniospinal irradiation for others. RESULTS: For the chemoradiotherapy group (n = 28), median follow-up was 7 years. No patient died. The freedom from progression (FFP) rate was 88% at 5 years and 80% at 10 years. In 4 patients, disease recurred 1.1 to 6.8 years after diagnosis. All were young male patients who received 30.6 Gy to local fields after complete response to chemotherapy. The FFP rate was 88% for local irradiation vs. 100% for more extensive fields (p = .06). For the radiotherapy-alone group (n = 31), median follow-up was 15 years. Overall and disease-free survival rates were 93% and 93% at 5 years and 90% and 87% at 15 years. In 5 patients, disease recurred 1.1 to 4.9 years after diagnosis. Most patients in this group were young men 18 to 23 years of age with suprasellar primary disease treated with about 50 Gy to local fields. The FFP rate was 44% for local irradiation vs. 100% for more extensive fields (p < .01). CONCLUSIONS: The addition of neoadjuvant chemotherapy to local-field radiotherapy reduced central nervous system cancer recurrence when high-risk patients were excluded by thorough pretreatment staging. There was trend toward improved central nervous system tumor control when larger fields (whole brain, whole ventricle, or craniospinal axis) were used.

Primary diffuse leptomeningeal gliomatosis.

BACKGROUND: Primary diffuse leptomeningeal gliomatosis (PDLG) is a rare presentation of a primary central nervous system glial tumor. METHODS: Four case reports of PDLG in young males aged 14-24 years are presented. These reports are discussed in the context of the existing literature. RESULTS: The clinical presentation of 4 new cases of PDLG resembled chronic meningitis with and without polyradiculopathy. Spinal fluid studies are typically nondiagnostic, but characteristically show elevated opening pressure, an elevated protein level, and a relative paucity of cellular reaction. An accurate antemortem diagnosis required contrast-enhanced imaging and meningeal biopsy in all 4 of our cases. Treatment strategies including craniospinal radiation and chemotherapeutic approaches, alone or in combination, have not been proven to alter the course of the disease. Initial responses to temozolomide and radiation treatments in all 4 of our cases were promising, resulting in temporary stabilization of the disease and prolonging life expectancy over what was previously reported in the literature. CONCLUSION: Total neuroaxis contrast-enhanced MRI scanning is required for directing biopsy confirmation and detecting the extent of the disease. More effective therapeutic strategies are needed, but the combination of temozolomide and radiation therapy may slow disease progression.

Central nervous system tumors.

Central nervous system tumors are relatively common in the United States, with more than 40,000 cases annually. Although more than half of these tumors are benign, they can cause substantial morbidity. Malignant primary brain tumors are the leading cause of death from solid tumors in children and the third leading cause of death from cancer in adolescents and adults aged 15 to 34 years. Common presenting symptoms include headache, seizures, and altered mental status. Whereas magnetic resonance imaging helps define the anatomic extent of tumor, biopsy is often required to confirm the diagnosis. Treatment depends on the histologic diagnosis. Benign tumors are usually curable with surgical resection or radiation therapy including stereotactic radiation; however, most patients with malignant brain tumors benefit from chemotherapy either at the time of initial diagnosis or at tumor recurrence. Metastases to the brain remain a frequent and morbid complication of solid tumors but are frequently controlled with surgery or radiation therapy. Unfortunately, the mortality rate from malignant brain tumors remains high, despite initial disease control. This article provides an overview of current diagnostic and treatment approaches for patients with primary and metastatic brain tumors.