Low+Grade+Astrocytoma

Protoplasmic Fibrillary Pilocytic Gemistocytic Pilomyxoid Pelomorphic Xanthoastrocytoma The RTOG uses a staging system taking into account; age, Karnofsky performance, histology, mental status, extent of surgery, time between symptoms and treatment onset, neurologic function, and radiation therapy doses. [4] Yet another multifaceted system with room for error. Attatched is a Karnofsky Performance Scale.  || With Low-Grade Astrocytomas surgery and total resection is the gold standard of care. If this is not possible a subtotal resection also improves the outcome. Post-op radiotherapy may be used.[6] The dose is 50-55 Gy in 1.8-2 Gy fractions. The treatment fields would include the tumor and a 3 cm. margin.[5] No chemotherapy is recomended unless there is a recurrence or it progresses to a higher grade lesion.[6] || || 2. Reference: Jallo GI. //Low-Grade Astrocytoma//. eMedicine. Available at: []. Accessed: May, 30, 2012. 3. //Pediatric Oncology Education Material//. Astrocytoma. Available at: []. Accessed: May 30, 2012. 4. Washington, Charles M. //Principles and Practice of Radiation Therapy.// Third ed. St. Louis: Mosby; 2010 5. Chao, K.S. Clifford //Radiation Oncology Management Decisions.// Third ed. Philadelphia: LWW; 2011 6. Jallo GI, Ramachandran TS, Benardete EA, et al. //Low grade Astrocytoma//. Jan. 8, 2010. Available at: [|http://emedicine.medscape.com/article/1156429-overview#showall]. Accessed May 31, 2012. 7. Emami B, Lyman J, Brown A, et al. Tolerance of normal tissue to therapeutic irradiation. //Int J Radiat Oncol Biol Phys.// 1991;109-122. []. Accessed May 31, 2012. || Back to Week 2
 * **Epidemiolgy:** || Low-grade astrocytomas are more common in adults than in children. The incidence rate is approximately 1.3 per 100,000 per year. Of these, 0.9 were symptomatic. [1] ||
 * **Etiology:** || Ionizing radiation and immunosuppression are risk factors. Astrocytomas occurring in an irradiation portal are sevenfold in those who survived more than three years after treatment for childhood malignancies with high radiotherapy doses. Syndromes such as Cowden’s syndrome, Li-Fraumeni and Neurofibromatosis type 1 are autosomal dominant and can be associated with astrocytomas. Li-Fraumeni is associated with a p53 germline mutation. Approximately 12% of families with this germline mutation have brain tumors. Other risk factors implicated but not yet proven include the ingestion of nitrosamines, work in the petroleum industry, exposure to electromagnetic radiation, and ingestion of aspartame. [1] ||
 * **Signs & Symptoms:** || An important indicator is change in consciousness but is difficult to test because a base line is difficult to establish due to the slow growing nature of the tumor. A better indicator could be lethargy and mood changes. Seizures, headaches, weakness or numbness (gradual onset) are an indicator of elevating intracranial pressure (obstructing cerebrospinal fluid pathways,) hydrocephalus, paralysis, sensory deficits aberrant behavior. [1] ||
 * **Diagnostic Procedures:** || Diagnostic procedures: CT, PETCT and MRI. MRI rendering the better of the two images due to the attenuation of the tumor verse surrounding tissue, CT without contrast will not show extent of tumor. A biopsy of the tumor can be done as well.[1] ||
 * **Histology:** || These tumors may have endothelial proliferation and marked atypia; nevertheless, they are slow growing and well circumscribed.[2] This subset comprises juvenile pilocytic astrocytoma (JPA) and its variant a juvenile pilomyxoid astrocytoma, pleomorphic xanthoastrocytoma (PXA), and subependymal giant-cell astrocytoma (SGCA). Low-grade astrocytomas generally cause symptoms by perturbing cerebral function (eg, seizures), elevating intracranial pressure (ICP) by either mass effect or obstructing cerebrospinal fluid (CSF) pathways (ie, hydrocephalus), or causing neurologic (and sometimes endocrine) abnormalities (eg, paralysis, sensory deficits, aberrant behavior, headaches).[2] The different types of histology of Low-Grade Astrocytoma are listed below[3]:
 * Usually cortical
 * Abundant cytoplasm
 * Most common histological variant
 * Diffuse or circumscribed
 * Well-differentiated
 * Pilocytes
 * Hair-like glial processes
 * Well-differentiated
 * Cerebral hemispheres
 * Large, round cells
 * Eosinophilic cytoplasm
 * More aggressive subset of JPA’s
 * Previously identified as JPA’s
 * Primarily in the hypothalamic region
 * Peripheral hemispheric lesions
 * Often involve leptomeninges
 * More aggressive histology
 * Rare
 * Unique to children ||
 * **Lymph node drainage:** || Since there is an absence of lymphatics in the brain, there is no lymphatic drainage due to the blood brain barrier[2]. ||
 * **Metastatic spread:** || Unlike other systemic tumors, metastasis of astrocytomas is exceedingly rare. Clinical decline and tumor associated morbidity and mortality are almost always associated with local mass effects on the brain by a locally recurrent intracranial tumor[2]. ||
 * **Grading:** || The grade of a tumor is based on its aggressiveness of growth and cellular differentiation. Grade is determined by microscopic examination of tumor cells and is important in predicting the prognosis of a CNS tumor diagnosis. Grade and stage give the physician an accurate description of the tumor so that they may treat it effectively. CNS tumors can be grouped in to benign, low-grade or malignant, and high grade. A system known as the Kernohan Grading System, which is a four grade system has also been used. This system takes in to consideration; cellularity, anaplasia, mitotic figures, giant cells, necrosis, blood vessels and proliferation. Because of the many factors, this grading system is confusing and difficult to use.[4] ||
 * **Staging:** || There are no universal staging systems for CNS tumors which can be confusing and can lead to problems when diagnosing. The American Joint Committee on Cancer uses a GTM system; grade (G), Tumor type (T), and Metastasis (M).
 * **Radiation side effects:** || Depending on the location, treatment type, and extent of expansion around the tumor site, many side effects are possible but not all likely. Many of them include:
 * Nausea vomiting
 * Radiation dermatitis
 * Hair loss in treatment field
 * Inflammation of outer middle or inner ear and other ear damage, if in the treatment area, may cause temporary or permanent hearing loss.
 * Fatigue
 * Blood counts may decrease with large treatment volumes
 * Somnolence syndrome, occurs 6-12 weeks post radiation caused by damage to oligodendroglial cells.
 * Focal radiation necrosis can appear 6 months to years post radiation.
 * <span style="color: #7030a0; font-family: 'Times New Roman','serif'; font-size: 16px;">Cataracts, retinopothy if eye is included in field
 * <span style="color: #7030a0; font-family: 'Times New Roman','serif'; font-size: 16px;">Visual degradation if the optic nerve and or chiasm are included with blindness at doses of 50 to 55 Gy.
 * <span style="color: #7030a0; font-family: 'Times New Roman','serif'; font-size: 16px;">Hypothalamic-pituitary doses of 20 Gy or more can cause insuficiant hormone production. Brain irradiation can impact critical thinking, short term memory, and learning ability.[5] ||
 * **Prognosis:** || Low grade Astrocytomas are a grade II tumor. They are slow growing and rarely spread to other parts of the central nervous system. The average survival is 7.5 years. Over time some of these tumors do progress into higher grade lesions, and are fatal.[6] ||
 * **Treatments:** || [[image:uwlmedicaldosimetry2012/low gradeastro .jpg width="208" height="277" caption="low-grade Astrocytoma"]]
 * **TD 5/5:** || ** TD 5/5 values from Emami 1991 [7] **
 * **References:** || 1. Lenhard RE, Osteen R, Gansler T. //The American Cancer Society’s Clinical Oncology//. Williston, VT: Blackwell Publishing, Inc; 2001.