Extensive resection prolongs survival among patients with low-grade glioma
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Maximal resection of low-grade glioma shortly after diagnosis may lead to longer survival, according to research published in the Journal of Clinical Oncology.
The findings of the University of California, San Francisco-led study differ from prior research that indicated extensive resection may not be necessary, researchers wrote.
“I believe this study represents a paradigm shift in the management of low-grade malignancies, particularly for oligodendrogliomas,” Annette Molinaro, PhD, professor in the UCSF department of neurosurgical surgery and member of Weill Institute for Neuroscience, told Healio. “We now know that if the surgeon can safely go beyond the margin of the tumor, it will reduce the risk for malignant transformation. This is a game-changer for patients with low-grade gliomas.”
Background
Due to their nature, low-grade gliomas are locally invasive and prone to malignant transformation if proper care is delayed.
WHO reclassification has resulted in separate clinical diagnoses of diffuse gliomas based on tumor histology and molecular characteristics.
Prior to the reclassification in 2016, extensive tumor resection to prolong survival had been standard of care; however, since the reclassification, studies have challenged the need for maximal surgery in low-grade glioma, particularly the oligodendroglioma subtype.
Methodology
Molinaro and colleagues conducted a 20-year retrospective study of 392 patients, examining the effects of volumetric extent of surgical tumor resection and molecular and clinical variables on OS and PFS among adults with WHO grade 2 IDH-mutant astrocytoma and IDH-mutant 1p19q codeleted oligodendroglioma.
The study included 202 patients with astrocytoma (median age at diagnosis, 35.1 years; 56.4 % men) and 190 patients with oligodendroglioma (median age at diagnosis, 42.6 years; 55.3% men).
Researchers defined OS as the time from surgery (or biopsy if before surgery) until death or last contact date and PFS as time between surgery/biopsy and tumor progression/death. They validated OS results in two external cohorts that included 365 patients.
Median follow-up was 11.7 years (95% CI, 10.8-12.8).
Results
Patients with larger postoperative and/or preoperative astrocytoma survived a median 9 years after diagnosis, compared with more than 20 years among those with smaller residual tumors. Meanwhile, patients with larger postoperative and/or preoperative oligodendroglioma lived a median 19.9 years, compared with more than 20 years among those with smaller pre- and postoperative tumors.
Results showed median PFS of 8.65 years (95% CI, 7.3-9.7).
Researchers reported longer median OS among those who underwent gross total resection vs. those with residual tumors (astrocytoma group, 16.2 years vs. 11.4 years; oligodendroglioma group, > 22.2 years vs. 22.2 years). Gross tumor resection plus, in which tumors and a margin of apparently healthy tissue are resected, resulted in longer survival for patients with astrocytoma but no significant survival benefit for patients with oligodendroglioma.
“The most surprising finding was the length of time needed in patient follow-up to see the effect of resection,” Molinaro told Healio. “We believe our results are contradictory due to our study’s large sample size and length of follow-up.”
The researchers concluded that at least 75% of tumor must be resected to prolong OS and at least 80% to prolong PFS across both low-grade glioma subtypes.
Next steps
Researchers plan to further study the relationship between the extent of resection and brain function/survival among patients with the diffuse low-grade glioma subtypes.
“The next steps are to investigate the interaction between tumor resection, neurological function and survival and derive a threshold for resection beyond the tumor margin,” Molinaro said.
For more information:
Annette Molinaro, PhD, can be reached at 1450 3rd St., San Francisco, CA 94158; email: annette.molinaro@ucsf.edu.
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Hervey-Jumper SL. et al. J Clin Oncol. 2023;doi.10.1200/JCO.21.02929.
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