The trick to treating low-grade gliomas is to remove as much of them as possible soon after diagnosis, researchers at University of California, San Francisco found.
“Our findings put an end to the controversy that maximal resection [tumor removal] may not be required for some low-grade gliomas,” said study co-author Dr. Shawn Hervey-Jumper, an associate professor in the UCSF department of neurological surgery.
Low-grade gliomas are diagnosed in 20,000 people, mostly young adults and those in midlife, each year in the United States, the study noted. After surgery, undetectable pockets of tumor cells grow slowly. This leads to recurrence and eventually malignancy and death, often in less than two years.
This diffuse low-grade glioma has two subtypes, called astrocytoma IDH-mutant and oligodendroglioma IDH-mutant 1p19q-codeleted.
Researchers followed 392 patients at UCSF with diffuse low-grade gliomas for up to 20 years for this study. They validated their results with two groups of patients from Brigham and Women’s Hospital in Boston and St. Olavs University Hospital in Norway.
“Studies that did not follow patients for as long as we did have raised questions about the need for maximal surgery, especially in oligodendroglioma. But we found that resecting as much as possible soon after diagnosis offered a distinct survival advantage when we looked at the disease trajectory 10 years later,” study co-author Annette Molinaro, a professor in the UCSF department of neurosurgical surgery, said in a university news release.
The researchers predicted that at least three-quarters of a tumor needs to be removed to improve long-term outcomes.
Patients who had larger post-operative and/or pre-operative astrocytoma lived a median of nine years after diagnosis, compared to more than 20 years for those with smaller residual tumors.
Patients with larger post-operative and/or pre-operative oligodendroglioma lived a median of almost 20 years, compared to more than 20 years with smaller pre- and post-operative tumors, according to the study.
Patients who had a potentially riskier procedure, called gross total resection (GTR), lived longer than those with residual tumors. In GTR, surgeons remove all of the tumor visible on an MRI.
An even more significant surgical procedure called GTR-plus, which includes removing a margin of healthy tissue, extended the survival of astrocytoma patients, but not oligodendroglioma patients.
“When we see incidental small tumors, we don’t wait because we can get a better resection, which translates to improved survival. However, GTR and GTR-plus are never done at the expense of [brain] deficits,” said study co-author Dr. Mitchel Berger, also a professor in the UCSF department of neurological surgery.
The research team also tracked progression-free survival and malignant transformation-free survival, when the tumor escalates from a more manageable grade 2 to a grade 3 or 4.
Larger astrocytoma was associated with shorter progression-free and malignant transformation-free survival periods. Patients with smaller astrocytoma and all patients with oligodendroglioma survived longer with tumors that were either not progressing or had not yet undergone malignant transformation, the study found.
“Even for oligodendrogliomas, there is no question that maximal resection is critical for enhancing survival,” Hervey-Jumper said.
The findings were published Jan. 4 in the Journal of Clinical Oncology.
The National Cancer Institute has more on brain tumors.
SOURCE: University of California, San Francisco, news release, Jan. 4, 2023
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