Title: Fast Fact and Concept #66: Radiation for Palliation - Part 1
Author(s): Rutter C; Weissman DE
Radiation therapy (XRT) is used with palliative intent to improve quality of life by improving function and/or diminishing symptoms, most commonly pain, bleeding or pressure on vital structures. XRT is the use of ionizing radiation to damage a cell's DNA. This can happen to a DNA molecule itself (direct effect, less common) or to an oxygen compound (OH, HOOH) which then reacts with a DNA molecule (indirect effect, more common). Damage only occurs in cells within the Radiation Field -the area through which the radiation beam passes; both malignant and normal cells within the field are affected. Malignant cells are less efficient at repairing DNA damage and are, therefore, more likely to die. The goal is to design a radiation field that includes all of the tumor cells while excluding as much normal tissue as possible.
XRT can be delivered 1) from outside the body, External Beam Radiation (EBR ), 2) from within the body by placement of a radiation source near the cancer, Brachytherapy or 3) as a radio- pharmaceutical given by mouth or by intravenous injection (e.g. Strontium 89). In EBR, patients typically receive one fraction per day, but other schedules are sometimes used (e.g. Hyperfractionation = > 2 doses per day). Fractionation takes advantage of the different rates at which malignant and non-malignant cells repair damage caused by XRT; it gives normal tissues an opportunity to recover while continually reducing the tumor cell population.
Radiation doses are described in units called Gray (Gy) or centiGray (cGy): 1 Gy = 100 cGy. Note: in the older literature, the term Rad was used, 1 rad = 1 cGy. A Radiation Prescription includes the site being treated, beam orientation and number (e.g. two beams, AP and PA), beam type (photons or electrons) and energy (in Volts), dose per fraction (typical daily doses for palliative EBR range from 150-400 cGy), number of fractions per day, and total dose. A Radiation Boost is an extra dose of radiation, given during the last treatments, to a smaller field within the original field. The total administered dose is based on a balance between giving enough radiation to control the tumor while respecting normal tissue tolerance to minimize the risk of late side effects. Different tissues have different radiation tolerances; liver and kidney can only tolerate a small total radiation dose (< 2400 cGy), whereas bone and peripheral nerves can tolerate much larger total doses (>5000 cGy).
Prior to the first treatment, patients undergo Simulation, where the exact location of the field is mapped; tattoo marks are sometimes placed on the skin to help ensure that the treatment field can be reproduced in the correct location at every treatment. If the radiation prescription calls for daily fractions, patients come to the radiation therapy department once a day, five days a week. Most palliative XRT lasts one to three weeks (treatment for curative intent lasts 5-7 weeks). Treatments are delivered inside a shielded, enclosed room. A radiation therapist operates the radiation machine (typically a linear accelerator) from outside the room while watching the patient on a camera. Each daily treatment takes only a few minutes and is painless.
At least once a week patients see the radiation oncologist to evaluate response and assess/treat toxicity. Toxicity depends upon the area being treated and, except for fatigue, is limited to tissues within that field. Side effects can be early/acute, occurring during or shortly after treatment and resolving within one to two months (e.g. oral mucositis during oral radiation), or late, occurring months to years after treatment (e.g. coronary artery disease following chest radiation). Early toxicity is related to inflammation and death of rapidly dividing cells (e.g. skin, gut) while late effects result from vascular changes and cell death of slowly dividing cells. Radiation oncologists have a host of medications, salves, and mouth rinses to help alleviate acute toxicities.
Fast Fact #67, Palliative Radiation - Part 2
References Ciezki JP. Palliative Radiotherapy. Seminars in Oncology. 01-Feb-2000; 27(1):90-3 Kirkbride, P. The Role of Radiation Therapy in Palliative Care. Journal of Palliative Care. 1995; 11(1):19-26 Perez C, Brady L., Chao KSC, eds. Radiation Oncology: Management Decisions. 3rd ed. Philadelphia: Lippincott-Raven 1999 Tisdale BA. When to Consider Radiation Therapy for Your Patient. American Family Physician 1999;59(5)
Copyright and Referencing Information: Users are free to download and distribute Fast Facts for educational purposes only. Citation for referencing Fast Facts and Concepts #66 Radiation for palliation-Part 1. Rutter C and Weissman DE. April, 2002. End-of-Life Physician Education Resource Center www.eperc.mcw.edu.
Fast Facts and Concepts was originally developed as an end-of-life teaching tool by Eric Warm, MD, U. Cincinnati, Department of Medicine. See: Warm, E. Improving EOL care--internal medicine curriculum project. J Pall Med 1999; 2: 339-340.
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Creation Date: 4/2002
Purpose: Instructional Aid, Self-Study Guide, Teaching
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Keyword(s): Radiation, Chemotherapy
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