Retroperitoneum

•lipomas •liposarcomas Children = rhabdomyosarcoma and lymphoma •majority develop germ cell tumors² Frequency: •lipomas occur in 1% of the population⁵ •liposarcomas represent 0.1% of all cancers but are the most common retroperitoneal sarcoma³ •rhabdomyosarcoma is the most common of the soft tissue sarcomas in children; soft tissue sarcomas make about up 3% of childhood cancers⁴ •lymphomas constitute 10-12% of childhood cancers⁵ || •Liposarcomas - no well established causative factor has been identified but trauma has been implicated.⁷ •Rhabdomyosarcoma - cause is unclear but several genetic syndromes and environmental factors are associated with increased prevalence.⁸ •Lymphoma - exact cause of lymphoma is unknown but several factors have been linked to increased risk: age, infections (HIV, HTLV-1, Epstein-Barr, Helicobacter pylori), medical conditions (HIV, autoimmune disease, diseases requiring immune suppressive therapy, inherited immunodeficiency diseases) and exposure to toxic chemicals (pesticides, herbicides, benzene, black hair dye).⁹ || ​•patients present with complaints of abdominal pain or a mass in 60-80% of cases •50% of patients have weight loss and loss of appetite at diagnosis. •patients with sarcomas tend not to seek medical treatment until the tumor are large because these tumors are usually asymptomatic. Patients with a germ cell tumor or lymphoma become more acutely ill •several retroperitoneal tumors are associated with paraneoplastic syndromes •germ cell tumors can cause precocious puberty in children and neutoblastoma can produce opsoclonic myoclonus •retroperitoneal liposarcoma or lipoma can produce intermittent hypoglycemia •extraadrenal retroperitoneal paraganglioma can produce symptoms of excessive catecholamine¹ || Diagnositc workup should include:¹ •thorough history and physical •complete blood cell count and studies to assess baseline bone marrow, hepatic and renal status •CT •CT guided needle biopsy or laparotomy •MR •simple radiographs² || Malignant Tumors: Lymphoma 27%, Liposarcoma 18%, Fibrosarcoma 11%, Leiomyosarcoma 8%, Neuroblastoma 8%, Unclassified sarcoma 6%, Rhabdomyosarcoma 4%, Mesodermal sarcoma 2%, Neurofibrosarcoma1%, Myxosarcoma 1%, Malignant fibrous histiocytoma 1%, Hemangiosarcoma 1%, Schwannoma 1%, Carcinoma 3%, Teratocarcinoma 1%, Unclassified tumor 4%, Metastatic tumor 3%¹ ||
 * ​ ​Epidemiology: || ​Adults = mesenchymal neoplasms
 * Etiology: || •While the exact etiology of lipomas remains uncertain, speculation of a link between trauma and subsequent lipoma formation exists and an association with gene rearrangement of chromosome 12 has been established in the cases of solitary lipomas, as has an abnormality in the HMGA2-LPP fusion gene.⁶
 * Signs & Symptoms: || ​Clinical presentation:
 * Diagnostic Procedures: || ​ Evaluation should focus on 3 factors: physiologic status of patient, extent of tumor involvement and histologic characteristics.
 * Histology: || Benign tumors: Lipoma 18%, Pheochromocytoma 12%, Ganglioneuroma 9%, Leiomyoma 6%, Teratoma 6%, Neurilemonma 4%, Neurofibroma 4%, Fibroma 3%, Paraganglimoa 2%, Lymphangioma 2%, Myoma 2%, Adenoma 2%, Adenoma 2%, Hemangioma 1%, Cyst 29%¹
 * Lymph Node Drainage: || For soft tissue sarcomas in the retroperitoneum, regional lymph node involvement is rare.¹² ||
 * Metastatic Spread: || The most common mode of expansion and invasion for these tumors is anteriorly into the abdominal cavity. Adjacent organ involvement is 60-70%.¹ ||
 * Grading: || Please see the "Classifications" table in the Staging Section below.¹¹ ||
 * Staging: || AJCC/TNM (based on histology)¹

The tables below show the AJCC classification and staging for soft tissue sarcomas. This staging system is better used for extremity sarcomas, but is also commonly used when staging retroperitoneal sarcomas. Retroperitoneal sarcomas are usually staged as Stage IIB or Stage III due to being large (greater than 5 cm) and deep to the superficial fascia.¹¹

|| For surgical resection only: 45% of patients survived for 5 years after complete excision. Only 8% survived after a partial excision.¹ Chemotherapy: Disease-free survival for patients who have a complete response to chemo is 75% to 95% as compaired to 5% for not a complete response. If the disease is present after retroperitoneal dissection, a dose of 40 to 45 Gy can be delivered.¹ ||
 * Radiation Side Effects: ​ || The acute sequelae of treatment with irradiation are nausea and vomiting. The long term major sequelae of surgery and irradiation are small bowel enteropathy (which is linked to the number of laparotomies the patient has had and irradiation dose and volume), and small bowel obstruction.¹ ||
 * Prognosis: || Prognosis factors are histology, invasiveness, and recectability of retroperitoneal.
 * Treatments: || ** General Management **
 * In past, surgical resection was the only means of achieving a cure in most patients wtih retroperitoneal tumors; this is still true in soft tissue sarcomas.
 * Nonresectability criteria include involvement of the aorta, vena cava, iliac or superior mesenteric vessels, as well as spinal cord or nerve plexus, peritoneal seeding, and distant metastases.
 * Radiation therapy is usually required in most malignant retroperitoneal tumors because of their infiltrative nature into retoperitoneal soft tissues.
 * A strong rationale exists for th euse of preoperative irradiation to decrease the likelihood of tumor seeding; this facilitates complete tumor resection and minimizes the risk of complicaitons.
 * Chemotherapy **
 * The role of chemotherapy in childhood rhabdomyosarcoma is well established; vincristine sulfate, doxorubicin, actinomycin D, and cyclophosphamide are the most commonly used agents.
 * Germ cell tumors are responsive to etoposide, cisplatin, and vincristine sulfate.
 * In both germ cell tumor and rhabdomyosarcoma, chemotherapy is often the initial treatment, followed by surgery and irradiation.
 * Radiation therapy techniques **
 * In the treatment of retroperitoneal soft tissue sarcomas with radiation therapy, we prefer preoperative irradiation, with consideration given to an intraoperative or postoperative boost.
 * Preoperative irradation is preferred for three reasons:
 * the extent of the local disease is usually easily defined by CT scan or MRI
 * radiation therapy morbidity is usually less since the large primary tumor mass acts to push normal tissues out of the irradiation field
 * preoperative irradiaiton may shrink the tumor, which will allow for a complete resection
 * When preoperative irradiation fields are designed, planning based on CT scannins is of great value. Contrast studies of the stomach or small bowel can be useful.
 * It is common for one kidney to be entirely in the irradiation field. In this situation, it is essential for the function of the other kidney to be documented and it should receive no more than 18 Gy.
 * Radiation therapy fields should be individualized for the exact location of tumor in each patient.
 * AP/PA or moderately oblique fields will often produce an optimal distribution.
 * Lateral fields should be used sparingly, as they often result in much larger volumes of normal tissue being irradiated, especially the liver in the upper abdomen.
 * Because these tumors originate in the retroperitoneum, the margins of the irradiation fields need to follow the anatomy of the tissues involved.
 * A 3 to 5 cm margin around gross tumor is usually adequate.
 * Generally, preoperative doses are 45 Gy, with approximately 4 weeks allowed to the time of surgery.
 * If the surgical margins are close or positive, additional postoperative radiation should be considered.
 * Normal tissue tolerances need to be respected as for preoperative therapy, but the total dose often is limited to 50 Gy because of the tolerance of small intestine and stomach.¹ ||
 * TD5/5: || Dose to the following organs should be considered:

Liver -- the whole liver can receive 20 to 30 Gy, with an upper threshold of 33 to 35 Gy. One-third to one-half of the liver volume can receive more than 40 Gy without complications. Kidney -- 1/3 can receive 50 Gy, 2/3 can receive 30 Gy, the whole kidney can receive 23 Gy. Spinal cord -- 45 Gy Stomach -- 1/3 can receive up to 60 Gy, 2/3 is 55 Gy, and the whole stomach tolerance is 50 Gy Small intestine -- 1/3 to 50 Gy and all to 40 Gy¹ || || 1. Chao KS, Perez CA, Brady LW. //Radiation Oncology - Management Decisions,// 2nd ed: 567-574. Philadelphia, PA//:// Lippincott, Williams & Wilkins, 2002. 2. Lenards, N. //Fundamentals of Clinical Oncology for Medical Dosimetrists. ​// Course content - Retroperitoneum, Slide 6. December, 2009. 3. BioInfoBank Library. []. Accessed January 18, 2010. 4. Wikipedia. []. Accessed January 18, 2010. 5. eMedicine. Non-Hodgkin Lymphoma. []. Accessed January 18, 2010. 6. eMedicine. Lipoma. [] Accessed January 18, 2010.. Accessed January 18, 2010. 7. eMedicine. Liposarcoma. []. Accessed January 18, 2010. 8. eMedicine. Rhabdomyosarcoma. []. Accessed January 18, 2010. 9. eMedicine. Lymphoma - causes. []. Accessed January 18, 2010. 10. Digitally Reconstructed Radiographs courtesy of Ginnie Dea, RT(T), Alta Bates Summit Comprehensive Cancer Center. 11. Pub Med Central. Retroperitoneal Sarcomas. []. Accessed January 22, 2010. 12. emedicine. Benign and Malignant Soft Tissue Tumors. []. Accessed January 22, 2010.
 * Planning Photos: || ​Digital reconstructed radiographs (DRR) of anterior and posterior retropertioneal fields including lungs but sparing the left kidney.¹⁰
 * References**

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