Oligodendroglioma

Please see Table 15-3 (below) for the histologic classificaton of tumors.¹ || Please see Table 15-2 (below) for grades of gliomas.³ || Please see Table 15-2 (below).¹ ||
 * Epidemiology: || Incidence of Disease ​: There is no difference among races of people. There is a male to female predominance of 2:1. Oligodendrogiloma is most common is middle-aged adults with a median age of about 50-60. In children only about 6% of cases are found to be in children.² ||
 * Etiology: || Risk & Causative Factors: No cause or risk factors are known. Occasional history in families.² ||
 * Signs & Symptoms: || Detection and Diagnosis: Headache and lethargy, seizures, weakness, motor dysfunction, and changes in behavior.² ||
 * Diagnostic Procedures: || Diagnosis may be accomplished by use of physical and neurologic examinations, CT, MRI, and biopsy. Physical and neurological examinations are indicated with new onset of any of the symptoms listed above. CT is almost universally available and, with contrast enhancement, is a reliable screening and diagnositc method in many cases. MRI is now more frequently used in patients with malignant brain tumors and may more accurately show the extent of the tumor. The most useful MRI studies are T1-weighted sagittal images, gadolinium-enhanced and unenhanced T1 axial images, and T2-weighted axial images. T1 images better domonstrate anatomy and areas of contrast enhancement; T2 images are more sensitive for detecting edema and tumor.¹ ||
 * Histology: || Neuroepithelial.¹
 * Lymph Node Drainage: || Absence of lymphatics in the brain therefore no lymphatic drainage due to the blood brain barrier. ||
 * Metastatic Spread: || ​Oligodendroglioma metastatic spread is via cerebrospinal fluid. Metastasis is rare but recurrence is high due to the infiltrating nature of gliomas.² ||
 * Grading:​ ​ ​ || World Health Organization (WHO) Grade II (low grade) and anaplastic grade III(high grade).²
 * Staging: || ​The stage system for brain tumors is the TNM system.
 * Radiation Side Effects: || The following side effects are possible with irradiation to the brain. The presence of these side effects varies due to tumor location, tumor size, and treatment technique/total dose.

Fatigue, decrease in blood counts, nausea, vomiting, headaches, skin irritation (on scalp) and short term memory loss can all occur during and shortly after the course of radiation treatment. Hair loss (temporary or permanent) can occur with doses of 20-40 Gy and doses greater than 40 Gy, respectively. Hormone insufficiency (if pituitary gland is in the field) will occur at a dose of 20 Gy. If the retina or lens is in the field, doses greater than 54 Gy can result in vision changes, cataracts or blindness. Serous otitis can occur when the ear falls in the treatment field at doses of 50 Gy. Neurologic deteriorations may be noticeable 6-12 weeks after treatment. Radiation necrosis may become evident 6 months to 3 years post radiation treatment.¹,⁵ || Brain: 45Gy (whole), 50Gy (2/3), 60Gy (1/3) Brainstem (large tumors): 50Gy (whole), 53Gy (2/3), 60Gy (1/3) Ear (acute serous otitis): 30Gy Ear (chronic serous otitis): 55Gy Lens: 10 Gy Optic Chiasm: 50 Gy Optic Nerve: 50 Gy Retina: 45 Gy⁴ ||
 * Prognosis: || Median survival for low grade oligodendrogliomas is 4-10 years. Median survival for anaplastic oligodendrogliomas is 3-4 years.² ||
 * Treatments: || * "Management of oligodendroglioma and mixed oligoastrocytoma is similar to that for low-grade astrocytoma.
 * A conservative approach for small, asymptomatic or completely resected lesions is close follow-up with deferred irradiation.
 * Adjuvant irradiation (50 to 55 Gy) can be offered for incompletely resected or symptomatic tumors.
 * Anaplastic oligodendroglioma is more aggressive than low-grade oligodendroglioma, although the outlook is still considerably better compared with glioblastoma multiforme. Maximal surgical resection is followed by adjuvant irradiation (60 Gy in 30 to 33 fractions to preoperative tumor volume with 2 to 3 cm margin).
 * Spinal seeding is unusual, even with high-grade tumors; therefore, prophylactic spinal irradiaiton is unnecessary.
 * Oligodendrogliomas have a particular senstivity to chemotherapy. In trials using procarbazine, CCNU, and vincristine (PCV), high response rates are seen for recurrent lesions. There is no evidence that adjuvant PCV chemotherapy adds to survival in patients with low-grade oligodendroglioma, although long peiods of tumor control have been reported with PCV used neoadjuvantly to defer radiation therapy. Adjuvant PCV chemotherapy may improve survival in these patients."¹ ||
 * TD5/5: || The following organs have the potential of being in the treatment field depending on tumor size and location.
 * Planning Photos: || Digital reconstructed radiographs (DRR) of an example of 3D treatment planning conformal irradiation technique using rapid arc in patient with brainstem mass.⁶



|| 1. Chao KS, Perez CA, Brady LW. //Radiation Oncology - Management Decisions.// 2nd ed. Philadelphia, PA//:// Lippincott, Williams & Wilkins; 2002:129-156. 2. eMedicine. []. Accessed January 14, 2010. 3. Prados M. //Brain Cancer Atlas of Clinical Oncology.// 1st ed. Hamilton, ON: BC Decker; 2002:281. 4. Wikibooks. Radiation Oncology/Toxicity/Emami. []. Accessed January 15, 2010. 5. Washington CM, Leaver D. //Principles and Practice of Radiation Therapy//. 2nd ed. Philadelphia, PA: Mosby, Inc; 2004:736-7. 6. Digitally Reconstructed Radiographs courtesy of Ginnie Dea, RT(T), Alta Bates Summit Comprehensive Cancer Center. Ginnie is bright blue. Bridget is green. Sheri is brown. Zack is purple.
 * References**