Low+Grade+Astrocytoma

CT scanning in a typical case reveals a nonenhancing lesion whose density is lower than that of the surrounding brain. A mass effect upon surrounding ventricular structures is common. When the MR images, the lesion typically presents as a low-intensity area on the T1-weighted images, whereas there is almost always an increase in signal intensity corresponding with an increase in relaxation time on T2-weighted images. The area of increased signal is usually homogeneous and well circumscribed, with no evidence of hemorrhage or necrosis. In many cases, it is difficult to differentiate on MR scans the tumor itself from surrounding areas of edema. Although the data are still not definitive, it does not appear that the use of an MRI contrast agent such as gadolinium will appreciably improve the ability to detect small lesions. Recent studies employing serial stereotactic biopsies of various regions of CT- and MR-defined abnormalities in patients with gliomas have indicated that there is infiltration of tumor cells into areas that were previously thought to represent only edematous white matter. There also would appear to be a role for positron emission tomography (PET) scanning in the diagnosis and treatment of these patients. A low-grade astrocytoma will be hypometabolic and therefore "cold" on PET scanning. However, when dedifferentiation to a more malignant state occurs within a low-grade astrocytoma, this area will be hypermetabolic and consequently will appear as a "hot spot" on PET scanning. This information may be extremely valuable in determining a site for stereotactic biopsy and/or determining whether the patient should be treated with postoperative radiation therapy. Fig 4. Low-grade astrocytoma and anaplastic astrocytoma. Short echo time (TE) MR spectra of 2 anaplastic astrocytomas (//A//, //-B//) and of low-grade astrocytoma (//C//) with corresponding MR images indicating the regions of interest are shown. The 3 spectra are scaled according to measured concentrations to allow direct comparison. Astrocytomas appear to be quite heterogeneous. Note the striking difference in total choline (tCho) in spectra A and B, tumors of the same diagnostic name. The prominent scyllo-inositol (sI) observed in spectrum C is not representative for all astrocytoma. Picture courtesy of American Journal of Neuroradiology. [] || Grade II astrocytoma is also cal﻿led low-grade astrocytoma or diffuse astrocytoma and is usually an infiltrating tumor. This tumor grows relatively slowly and usually does not have well-defined borders. It occurs most often in adults between the ages of 20 and 40. || Postoperative irradiation in subtotally resected pilocytic astrocytoma may be appropriate depending on symptoms, extent of residual disease, availability for follow-up, and feasibility of repeat surgical excision. The post-op radiation dose is 50-55Gray (Gy) (1.8-2.0Gy fractions). Nonpilocytic Astrocytomas: Treatment is recommended for patients with increasing tumor size, new neurologic symptoms, refractory seizures, or evidence of malignant transformation. The postoperative radiation dose is 50-55Gy. The irradiation fields cover the preoperative tumor volume with a 2 centimeter margin. Chemotherapy is not used until there is a recurrence or transformation. [1]
 * Epidemiology: || Astrocytomas make up 60% of brain tumors. There are 7-10 cases per 100,000 population discovered per year. Grade 1 astrocytomas (pilocytic Astrocytomas) are seen in the cerebellum, brainstem, and optic nerves of children. Grade 2 astrocytomas are seen in the cerebral hemispheres of 20-40 year old individuals and high grade astrocytomas, which are most malignant in their course, are seen in patients in their 50s and 60s. ||
 * Etiology: || Astrocytomas of all grades have been associated with cranial therapeutic irradiation, exposure to pesticides, and N-Nitroso compounds. Evidogenous mutations caused by these agents or other causes act to provide astrocytomas. ||
 * Signs & Symptoms: || They are generally present with a long history of signs and symptoms. They are often non-specific and non-localizing initially. School age children may present with personality changes, declining academic performance, fatigue, and intermittent headaches related to increased intracranial pressure. ||
 * Diagnostic Procedures: || In the past, the neuroradiologic procedures used to diagnose the lesion included isotope brain scanning and cerebral angiography. The isotope brain scan might or might not demonstrate the lesion; the angiogram would usually demonstrate a mass lesion without evidence of abnormal vascularity. In recent years, the diagnostic procedures of choice have become CT and/or MR imaging. Because it is not uncommon to find low-grade astrocytomas that are detected only on MRI (after normal CT scans), most believe that MRI is the most sensitive test available today to diagnose these lesions. At surgery, the use of intraoperative ultrasonography has been reported to be extremely helpful in outlining the extent of the lesion.
 * Histology: || ﻿An astrocytoma is a type of glioma that develops from star-shaped cells (astrocytes) that support nerve cells. It is slow growing, and rarely spreads to other parts of the CNS. The borders are not well defined, and it is common among men and women in their 20s-50s. They are a heterogeneous group of intrinsic central nervous system neoplasms that share certain similarities in their clinical presentation, radiologic appearance, prognosis, and treatment. ||
 * Lymph Node Drainage: || To my understanding and research, I have found that there is no drainage due to the blood brain barrier present. Also, the fact that there is an absence of lymphatics in the brain leads to this conclusion. ||
 * Metastatic Spread: || Tumor spread, when it occurs, is usually by contiguous extension; dissemination to other central nervous system sittes may rarely occur. Although metastasis is unlikely, tumors may be of multifocal origin, especially when associated with neurofibromatisis type 1. ||
 * Grading: || Grade I astrocytoma is usually a noninfiltrating tumor. The most common type of grade I astrocytoma is pilocytic astrocytoma which is also known as juvenile pilocytic astrocytoma or JPA. This tumor grows slowly but can become very large. Pilocytic astrocytoma occurs most often in the cerebellum, cerebrum, optic nerve pathway and brainstem. This tumor occurs most often in children and teens and accounts for 2% of all brain tumors.
 * Staging: || There are several different systems for staging astrocytomas. The World Health Organization (WHO) system is the most common; it has four grades of increasing severity based on the appearance of the astrocytoma cells. Other methods of staging correspond fairly closely to the WHO system. Grades I and II are sometimes grouped together and referred to as low-grade astrocytomas. Over time, tumors may progress from a low-grade form with a relatively good prognosis to a higher grade form and poorer prognosis. Additionally, tumors may recur at a higher grade. ||
 * Radiation Side Effects: || T here are cognitive side effects of treatment including poor short-term memory and adminished ability to concentrate. There have been studies of people with low-grade astrocytomas treated with focal radiation therapy, which found a lack of cognitive effects in the first few years after treatment, providing reassurance that current radiation therapy procedures are well-tolerated. These studies also show that fatigue and depression are common in patients with low-grade astrocytomas whether or not they receive radiation therapy. Thus, some symptoms commonly attributed to radiation therapy may be more appropriately blamed on the tumor itself. ||
 * Prognosis: || A great deal of effort has been expended to determine which factors might be of significance in determining the prognosis in a particular patient. All of the recent studies seem to agree that a young age at the time of diagnosis is by far the most important factor that correlates with a prolonged survival. There have been some findings that indicate other factors correlating with a prolonged survival were gross total surgical removal, lack of a major preoperative neurological deficit, long duration of symptoms prior to surgery, seizures as a presenting symptom, lack of a major postoperative neurological deficit, and having had surgery performed within recent decades. Most would agree that lobectomy has no place in the surgical treatment of these tumors and that a gross total resection should be attempted if it can be accomplished without a significant risk of producing a neurological deficit.  ||
 * Treatments: || Pilocytic Astrocytomas: Surgery is the treatment of choice. In completely resected tumors, no adjuvant therapy is needed.

 A brainstem pilocytic astrocytoma treated with CyberKnife radiosurgery. || Low Grade Astrocytoma: Standard dose (if radiation therapy is indicated), 50-55Gy. [1] || References: M.L. Grunnet, //Cerebellar Astrocytoma.// []. Accessed May 31, 2011 Pediatric Oncology Education Materials//. Astrocytoma//. [|http://www.pedsoncologyeducation.com]. Accessed June 1, 2011 CNS Clinic Jordan//. Low-grade Astrocytoma//. []. Accessed June 1, 2011. National Bran Tumor Society. //Low Grade Astrocytoma.// [|http://www.braintumor.org.] Accessed June 1, 2011. WebMD. //Brain Cancer.// []. Accessed June 3, 2011. //Astrocytoma.// []. Accessed June 4, 2011. American Brain Tumor Association. //Low Grade Astrocytomas.// []. Accessed June 4, 2011. [1] Chao C, Perez C, Brady L. Brain, Brainstem, and Cerebellum. //Radiation Oncology.// //2nd ed//. Philadelphia, PA: Lippincott Williams & Wilkins; 2002: 129-156. [2] Vann A, Dasher B, Chestnut S, Wiggers N. Central Nervous System Tumors. //Portal Design in Radiation Therapy. 2nd ed.// Columbia, SC: The R.L. Bryan Company; 2006: 59-69.
 * TD5/5: || TD 5/5: Normal Tissue Tolerances (Gy) (1.8-2.0 Gy per fraction). [2]