Chemotherapy-induced changes in tumor consistency can allow gross total resection of previously unresectable brainstem pilocytic astrocytoma

Abstract

Background: Low-grade gliomas (LGG) are described by the World Health Organization as Grades I and II. Among LGGs, the most common primary brain tumor is pilocytic astrocytoma (PA) and carries an excellent prognosis when treated with complete surgical resection. Cases, in which this is not possible, are associated with less favorable outcomes and worse progression-free survival.

Case description: This report describes a case of a 22-year-old male, who presented with progression of a primary brainstem tumor previously treated with stereotactic radiosurgery and chemotherapy. Patient underwent surgical exploration and was diagnosed with juvenile PA, but debulking was limited by the very dense and fibrous tumor. Complete surgical resection was not possible at this time. Despite efforts to treat with chemotherapy, the patient presented a year later with clinical deterioration and severe neurologic deficits, prompting surgical re-exploration. During the second operation, the tumor was found to have undergone very significant softening in consistency, allowing for gross total resection (GTR).

Conclusion: Aggressive treatment of brainstem LGG should be pursued whenever possible, given its generally favorable prognosis. Repeat microsurgical resection, even with a different approach, might be reasonable and safe. Finally, chemotherapy may be associated with changes in the tumor consistency that can render previously unresectable lesions amenable to successful aggressive resection.

Keywords: Brainstem low-grade glioma; Chemotherapy; Gross total resection; Pilocytic astrocytoma; Tumor consistency.

Figure 1:

Initial brain MRI: (a) Axial T1 image with contrast; (b) coronal FLAIR and (c) coronal T1 with contrast images, showing large left midbrain-pontine lesion at the time of stereotactic radiosurgery.

Figure 2:

Two years after stereotactic radiosurgery and first round of chemotherapy: (a) Brain CT showing hemorrhage in the dorsal aspect of the tumor. Brain MRI with contrast: (b) Axial T1 image demonstrating the lesion in the left brainstem and prominent temporal horns (arrows), suggestive of an obstructive hydrocephalus; (c) sagittal T1 image showing ring-enhancing mass.

Figure 3:

MRI images with contrast: (a) Immediate preoperative axial T1 views; (b) intraoperative Axial T1 views demonstrate an approximate 40% resection of the lesion (dotted arrow) and expected intraoperative pneumocephalus (solid arrows); (c) immediate preoperative coronal T1 views; (d) intraoperative coronal T1 views.

Figure 4:

Four months after partial resection and shunting; (a) non-contrast brain CT shows hemorrhagic component mostly in the posterior aspect of the tumor; (b) axial, (c) sagittal, and (d) coronal T1 MRI views with contrast, showing significant interval tumor enlargement with solid (solid arrows) and cystic (dotted arrows) components. At this point in the patient’s care, it was felt, he did not have many options left. He appeared to have either poorly tolerated, or did not respond to, chemotherapy. After two prior radiation treatments, he was ineligible for further radiation. Therefore, a multi-disciplinary decision was made to repeat neurosurgical intervention in an attempt to decompress the cyst and remove some more tumor, if feasible.

Figure 5:

Postoperative brain MRI: (a) Axial T1 image; (b) sagittal T1 image; and (c) coronal T1 image, demonstrating postsurgical changes after GTR of the left dorsal midbrain-pontine tumor.