Souweidane, Mark M.

Abstract BACKGROUND Accurate molecular diagnosis of infiltrating brainstem tumors, including diffuse midline gliomas and IDH mutant astrocytomas, is essential for prognostication and optimal therapy. Surgical biopsy of the brainstem carries risk of permanent neurological deficits and may yield insufficient or non-diagnostic tissue. We hypothesized that minimally invasive “liquid biopsy” analyzing circulating tumor cell-free DNA (cfDNA) in cerebrospinal fluid (CSF) could represent an alternative molecular diagnostic modality. METHODS We performed MSK-IMPACT, a New York State Department of Health authorized hybridization capture-based next-generation panel DNA sequencing clinical assay on 44 CSF samples from 37 unique patients with brainstem tumors. Ages at time of CSF collection ranged from 1–47 years (median: 29 years). For samples in which diagnostic alterations could not be detected, we performed a series of secondary analyses for known hotspot mutations such as H3F3A, IDH1/2, and BRAF, including manual review for mutant reads below the official clinical reporting threshold, as well as droplet digital PCR (ddPCR). RESULTS Among 44 samples included in this study, 10/44 (23%) samples had mutations detected by MSK-IMPACT using standard clinical calling criteria and 14 of the remaining 34 samples (41%) had supporting evidence of a diagnostically relevant mutation based on manual review. Testing by ddPCR was performed on 11 samples (based on DNA availability), uncovering 4 additional mutations. Overall positive diagnostic yield was 64% (28/44). In biopsied patients, CSF confirmed disease-defining mutations in 80% (16/20) of CSF samples, including H3F3A K28M (9/10; 90%) and IDH1/2 (5/6; 83%). Among 24 unbiopsied patients, a disease-defining mutation was identified in 60% (15/25) of CSF samples. CONCLUSIONS Analysis of CSF cfDNA in patients with brainstem tumors has a high diagnostic yield and obviates the need for tissue biopsy in a majority of patients. A tiered testing approach using next-generation sequencing and ddPCR assays helps maximize diagnostic information and sensitivity.

Abstract Background The study aimed to evaluate whether simplified chemotherapy followed by dose-reduced irradiation was effective for treating patients (ages 3–21 years) with localized germinoma. The primary endpoint was 3-year progression-free survival (PFS) rate. Methods Patients with a complete response to chemotherapy with carboplatin and etoposide received 18 Gy WVI + 12 Gy boost to the tumor bed. Patients with partial response proceeded to 24 Gy WVI + 12 Gy. Longitudinal cognitive functioning was evaluated prospectively on ALTE07C1 and was a primary study aim. Results One hundred and fifty-one patients were enrolled; 137 were eligible. Among 90 evaluable patients, 74 were treated with 18 Gy and 16 with 24 Gy WVI. The study failed to demonstrate noninferiority of the 18 Gy WVI regimen compared to the design threshold of 95% 3-year PFS rate, where, per design, patients who could not be assessed for progression at 3 years were counted as failures. The Kaplan-Meier (KM)-based 3-year PFS estimates were 94.5 ± 2.7% and 93.75 ± 6.1% for the 18 Gy and 24 Gy WVI cohorts, respectively. Collectively, estimated mean IQ and attention/concentration were within normal range. A lower mean attention score was observed at 9 months for patients treated with 24 Gy. Acute effects in processing speed were observed in the 18 Gy cohort at 9 months which improved at 30-month assessment. Conclusions While a failure according to the prospective statistical noninferiority design, this study demonstrated high rates of chemotherapy responses, favorable KM-based PFS and OS estimates in the context of reduced irradiation doses and holds promise for lower long-term morbidities for patients with germinoma.