Incidental Glioblastoma Tied to Better Outcomes

Jim Kling

January 18, 2022

The study was published as a preprint on on November 8. It has not yet been peer reviewed.

Key Takeaways

  • A retrospective study found better survival associated with incidental-discovered glioblastomas (iGBMs) that were treated early compared to other GBMs.

  • The findings suggest that early detection of GBMs may lead to better survival.

Why This Matters

  • With increased imaging and improved imaging technology, incidental discovery of intracranial neoplastic lesions is becoming more common.

  • Incidental lower-grade gliomas represent an estimated 3.8% to 17.2% of lower-grade gliomas, defined as having a steady growth rate less than 3.5 mm in diameter or 3.9 cm3 in volume per year.

  • High-grade gliomas and high-grade iGBMs have not been well characterized.

Study Design

  • Single center, retrospective analysis of 234 adult GBM and iGBM patients treated between August 2005 and October 2019. All patients had at least 6 months of follow-up.

  • iGBMs were defined as a GBM with no focal sign that was identified on radiologic images that were obtained for an unrelated reason.

  • The study excluded patients who initially had headaches accompanied by signs of intracranial pressure.

Key Results

  • Four patients (1.7%) had iGBM (one female, three men). Three cases were identified during a health checkup, and one during headache screening. All tumors were right-sided. Three patients had enhanced lesions. The patient with a nonenhanced lesion was followed up with MRI and underwent surgery when it became enhanced.

  • The time between lesion confirmation and surgery was a median of 13.5 days (range, 4–19).

  • Two lesions were in the temporal lobe, one in the parietal lobe, and one in the frontal lobe. The mean volume was 16.8 cm3 (range, 2.2 – 23.6).

  • Two iGBM patients had a total resection, and the other two had subtotal resection. All four patients had a Karnofsky Performance Score of 90 at hospital discharge.

  • Molecular studies showed that there were no IDH1/2 or H3F3A mutations. Two iGBMs had the TERT promoter mutation, and one had BRAF mutation. MGMT promoter methylation status was low in all four cases.

  • After resection, three patients underwent treatment with temozolomide (75 mg/m2 7 days/week with radiotherapy, then 150 – 200 mg/m2 during six cycles of adjuvant therapy). One patient underwent nimustine hydrochloride (100 mg/body) treatment. All received local brain radiotherapy (60 Gy in 30 fractions). None experienced severe adverse events due to chemotherapy.

  • All four patients had disease progression, and three died during the course of the study. The median progression-free survival was 11.5 months, and median overall survival was 20.0 months. These were longer than previous reports of 6.3 – 7.1 months and 10.1 – 15.2 months, respectively.

  • The tendency for asymptomatic iGBMs to be right-enhanced may be explained by the fact that the left hemisphere is dominant in 95% of right-handed and 70% of left-handed individuals.


  • The study was retrospective and had a very small sample size of iGBM, and it was conducted at a single institution.

Study Disclosures

  • The study was not funded. Two of the authors have received grants from Chugai Pharmaceutical, Eisai, Daiichi Sankyo, MSD, Toshiba, SBI Pharma, Glaxo, Abbvie, Ono, Stella-Pharma, Ohtuka, and Meiji-Seika.

This is a summary of preprint research, "The Clinical Characteristics and Outcomes of Incidentally Discovered Glioblastoma," led by Yoshitaka Narita, MD, PhD, of the National Cancer Center Hospital in Tokyo. It was published on in advance of peer-review and is provided to you by Medscape.

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