A case series was recently published in CNS Oncology that investigated whether adult pilocytic astrocytoma—a rare and highly vascular tumor—is responsive to bevacizumab treatment.
Bevacizumab, a monoclonal antibody that blocks vascular endothelial growth factor (VEGF) pathways, has been previously found to decrease the permeability of vasculature as well as perilesional edema in glioblastoma. Researchers hypothesized that APA may be uniquely receptive to treatments that block VEGF, such as bevacizumab, given the vascularity of the tumor.
Though juvenile pilocytic astrocytoma are curable with complete surgical resection, relatively few studies have researched APA. However, some retrospective studies and anecdotal reports suggest that APAs have a more aggressive clinical course compared with juvenile cases, with a higher incidence of recurrence and progression. Recurrence rates for APA have been reported as high as 30% to 42%, and currently no standard of care exists for the treatment of APA.
Researchers reported on 4 adult patients, aged 23 years to 66 years, with pathologically diagnosed World Health Organization grade 1 pilocytic astrocytoma and who had durable, robust response to bevacizumab at the time of recurrence. Three of the tumors were located in the cerebellum, tectum, and brainstem, with the last appearing in the lateral ventricle.
All patients were treated with bevacizumab at a dose of 10 mg every 14 days for 6 cycles at the time of recurrence. The treatment was well tolerated, and no patients experienced adverse events. Following bevacizumab administration, steroids were weaned and eventually discontinued in all patients.
At the conclusion of treatment, all patients had achieved a significant clinical and radiographic response. Magnetic resonance imaging (MRI) studies of each patient’s brain after 6 cycles of bevacizumab showed significant decrease or resolution of tumor contrast enhancement. In addition, all patients experienced a significant reduction in tumor size following treatment. Two of the patients experienced complete responses, with no radiographic evidence of tumor upon follow-up MRI.
The sustained decrease in tumor size and contrast enhancement after treatment suggest that bevacizumab may be an important agent to achieve durable disease control in APA. To date, there are no prospective studies evaluating the use of such treatments in APA, however. Due to the low incidence of the tumor, the authors say, future studies are warranted to further assess efficacy of bevacizumab treatment in APA.
Wasilewski A, Mohile N. Durable response to bevacizumab in adults with recurrent pilocytic astrocytoma [Published online April 9, 2018]. CNS Oncol. doi: 10.2217/cns-2017-0039.