10171-MPC-13 IDH-WILDTYPE LOWER-GRADE ASTROCYTOMA
Yoshinobu Takahashi, Takahiro Ogawa, Ichita Taniyama, Takumi Yamanaka, Seisuke Tanigawa, Hayato Takeuchi, Naoya Hashimoto- Surgery
- Oncology
- Neurology (clinical)
Abstract
BACKGROUND AND PURPOSE
In the WHO 2021 classification, glioblastoma is limited to IDH-wildtype and is diagnosed when microvascular proliferation and necrosis are present. Furthermore, even in the presence of morphologically low-grade findings, the diagnosis of glioblastoma is made if there is either EGFR gene amplification, TERT promoter mutation, or +7/-10 chromosome copy number alterations. Therefore, we investigated IDH wild-type lower-grade astrocytoma.
CASES
10 patients were included in this study. Sanger sequencing was performed for TERT promoter mutations, and MLPA was further implemented using probes for EGFR and PTEN genes in TERT wild-type cases. The threshold values for copy number change were homozygous deletion (x≤0.4), loss of heterozygosity (LOH) (0.4<x≤0.7), gain (1.3≤x<2.0), and amplification (x≥2.0). EGFR gain and PTEN LOH were used as surrogate markers for +7/-10 chromosome copy-number alterations.
RESULTS
Seven of these patients were diagnosed with glioblastoma, IDH-wildtype with a TERT promoter mutation. All three did not meet the diagnostic criteria for glioblastoma. All patients received temozolomide combination radiotherapy and maintenance temozolomide therapy. The median survival time of seven glioblastoma, IDH-wildtype patients was 616 days. Two patients who did not meet the diagnostic criteria for glioblastoma survived 510 and 583 days after initial surgery, respectively, and one patient was given the best supportive care policy at 518 days. Genetic analysis of all three cases showed TP53 LOH.
CONCLUSION
It was suggested that tumors with IDH wild-type low-grade astrocytoma that do not meet the diagnostic criteria for glioblastoma may have a poor prognosis. Although TP53 LOH was common, further investigation of specific genetic abnormalities is needed, and the classification and treatment strategy of these disease groups may be a challenge in the future.