Meningioma in a 9-year-old chocolate Lab: Medical oncology perspective

Dr. Lark WaltersWhen evaluating a patient with a suspected meningioma, additional staging after brain imaging should be considered. While meningiomas are typically solitary and have a low metastatic rate, second unrelated malignancies do occur.1 In a study of dogs with primary intracranial tumors, 23% were found to have another, unrelated malignancy at necropsy.2 In other studies of dogs receiving abdominal or thoracic imaging or both for staging or radiation planning purposes, 3% to 5% were found to have a secondary malignancy.3-5 In our clinical experience, a second unrelated malignancy is found with relative frequency in middle-aged to older patients, so we typically recommend full staging to assess overall health before moving forward with treatment of a primary tumor.

Limited information exists in the literature about the utility of chemotherapy for dogs with brain tumors, with even less data regarding treatment of meningiomas specifically. Lomustine, carmustine and hydroxyurea have been evaluated for the treatment of canine brain tumors, as each of these chemotherapy agents penetrate the central nervous system.1 Lomustine is a lipid-soluble alkylating agent that allows for its transport across the blood-brain barrier. In a study of dogs with intracranial masses that compared treatment with an antiepileptic (phenobarbital) and prednisone with or without lomustine, no significant difference in median survival time was found, suggesting that the addition of lomustine does not improve outcomes in dogs treated medically.6

In another study evaluating chemotherapy in dogs with brain tumors, the reported median survival time for dogs treated with prednisone alone was 14 weeks, while dogs receiving a combination of prednisone and hydroxyurea survived 28 weeks.1 Palliative care with antiepileptics and prednisone have also been evaluated, and an overall median survival time of 69 days was reported.7 Tumor location is prognostic, as dogs with supratentorial (cerebral) tumors have survival times greater than three months, and dogs with tumors in the cerebellum, pons or medulla have a worse prognosis, at approximately one month.7

Overall, the use of chemotherapy appears to have a minimal role in the treatment of canine meningiomas at this time, particularly for patients treated with surgery, radiation therapy or both. For patients treated medically, there are conflicting results regarding the benefit of chemotherapy in addition to antiepileptic drugs and corticosteroids.

References

1. Withrow SJ, Page R, Vail DM. Tumors of the nervous system. In: Small animal clinical oncology. 5th ed. St. Louis: Elsevier, 2013.

2. Snyder JM, Shofer FS, Van Winkle TJ, et al. Canine intracranial primary neoplasia: 173 cases (1986-2003). J Vet Intern Med 2006;20;669-675.

3. Bigio Marcello A, Gieger TL, Jiménez DA, et al. Detection of comorbidities and synchronous primary tumours via thoracic radiography and abdominal ultrasonography and their influences on treatment outcome in dogs with soft tissue sarcomas, primary brain tumours and intranasal tumours. Vet Comp Oncol 2015;13;433-442.

4. Magestro LM, Gieger TL. Detection of synchronous primary tumors and previously undetected metastases in 736 dogs with neoplasia undergoing CT scans for diagnostic, staging and/or radiation treatment planning purposes. Vet Comp Oncol 2016 May 2. [Epub ahead of print]

5. Rebhun RB, Thamm DH. Multiple distinct malignancies in dogs: 53 cases. J Am Animal Hosp Assoc 2010;46;20-30.

6. Van Meervenne S, Verhoeven PS, de Vos J, et al. Comparison between symptomatic treatment and lomustine supplementation in 71 dogs with intracranial space-occupying lesion. Vet Comp Oncol 2014;12;67-77.

7. Rossmeisl JH Jr, Jones JC, Zimmerman KL, et al. Survival time following hospital discharge in dogs with palliatively treated primary brain tumors. J Am Vet Med Assoc 2013;242;193-198.