Radiotherapy PDF

Introduction Radiation therapy: is the medical use of ionizing radiation to control or kill malignant cells directly or indirectly. Types of radiation for treatment: • Photons beam (x-ray and gamma ray) • Particles (Electron, protons, neutron, alpha ..) Sources of radiation? Three most common modes...

Introduction Radiation therapy: is the medical use of ionizing radiation to control or kill malignant cells directly or indirectly. Types of radiation for treatment: • Photons beam (x-ray and gamma ray) • Particles (Electron, protons, neutron, alpha ..) Sources of radiation? Three most common modes of nuclear decay Some examples of X-ray energies used in medicine are: ➢ Superficial X-rays – 35 to 60 keV ➢ Diagnostic X-rays – 20 to 150 keV ➢ Orthovoltage X-rays – 200 to 500 keV ➢ Supervoltage X-rays – 500 to 1000 keV ➢ Megavoltage X-rays – 1 to 25 MeV Definition of Radiotherapy • Radiation therapy is the medical use of ionizing radiation, generally as part of cancer treatment to control or kill malignant cells Radiation therapy Technique: Is a procedure to implement radiotherapy plan (Clinical, physical and technical) for cancer patient with consideration to anatomy of organ of interest, sensitive adjacent organs, physiology, patient position with best maneuvering utilization of radiotherapy accessories and equipment. Goals of Radiotherapy Radiation therapy is given for different aims: • Radical treatment • Palliative treatment • Adjuvant therapy • Enhancing the chance of operation Types of Radiation Therapy External beam (Teletherapy) Internal irradiation (Brachytherapy) – Intracavitary – Interstitial – Surface molds Mechanism of Radiation Therapy • Radiation therapy works by damaging the DNA of cancerous cells in the two ways :1. Direct ionization of the atoms which make up the DNA chain. 2. Indirect ionization happens as a result of the ionization of water, forming free radicals. High energy radiation (gamma rays, x-rays, electrons) directed to area of interest Some radiation interaction with water in the body leads to free radical formation which can damage DNA and other cellular structures; and eventually cell death and tissue injury occur Photon Therapy • In photon therapy, most of the radiation effect is through free radicals 1. Single-strand DNA damage (cell repair) 2. Double-stranded DNA (cell death) Radical Treatment • Radical radiotherapy is treatment delivered with intent to produce a high rate of local tumour control • Most radical treatments are given over 4-6 weeks, in 1.8 – 2 Gray fractions to a total dose of 55 - 74Gy THE normal tissues and cancers have variable and overlapping sensitivities to radiation – This limits our ability to optimize the treatment – Combined approaches (with chemotherapy, surgery, etc.) often needed Radiosensitive vs. Radioresistant Cancers • Radiosensitive • Radioresistant – Lymphomas – Melanoma – Germ cell tumors – Sarcomas – Small cell carcinomas – Glioblastomas Combination Treatment • Radiation therapy may be used alone or in combination with other treatments such as:1. Surgery 2. Chemotherapy 3. Immunotherapy Palliative Treatment • Palliative radiotherapy is given over a shorter period of time with larger fraction sizes but a lower overall dose • Treatment may be given as a:1. Single fraction:a) 8-10 Gy 2. Short fraction:a) 20 Gray /5 fractions b) 30Gy /10 fractions Advantages ● ● ● Allows for loco-regional treatment of cancer without direct removal of organs/tissues Can allow for organ preservation Less restricted by pre-existing medical conditions Disadvantages ● ● ● Almost impossible to avoid some damage to normal tissues (but repair/recovery possible) May involve multiple daily treatments over several weeks, especially for curative treatment Psychological aspects of “not removing” cancer April 11, 2001 December 6, 2000 (just prior to 1000cGy/1fr/1day orthovoltage treatment using 300kvp photons) Treated area close-up (1 year post radiation) Limitations of Radiotherapy Immediate symptom or pain relief does not occur Significant improvement may require a couple of weeks or more after radiotherapy Etiology of the symptoms needs to be clear before giving radiation Diffuse/extensive involvement of critical organs by cancer not usually well palliated by radiation ● ● ● ● TEAMWORK OF RADIOTHERAPY 1. 2. 3. 4. 5. 6. 7. Radiation Oncologist Medical Radiation Physicists Radiation Therapist Medical Dosimetrist Radiation Oncology Nurses Social Workers Dieticians Radiation Oncologist • Radiation oncologist is a physician who oversee the care of each cancer patient undergoing radiation treatment. • Duties :1. They develop and prescribe each cancer patient's treatment plan. 2. They make sure that every treatment is accurately given. 3. They monitor the patient's progress and adjust treatment to make sure patients get quality care throughout treatment. Medical Radiation Physicists • Medical physicist works directly with the radiation oncologist in the treatment planning and delivery. • Duties :1. They oversee the work of the dosimetrist and help ensure that complex treatments are properly tailored for each patient. 2. They are responsible for developing and directing quality control programs for equipment and procedures. 3. They are responsible for making sure the equipment works properly. Radiation Therapist • Radiation Therapist is an allied health professional who works in the field of radiation oncology and with radiation oncologists. • Duties :1. They administer the daily radiation treatment under the radiation oncologist’s prescription and supervision. 2. They maintain daily records and regularly check the treatment machines to make sure they are working properly. Medical Dosimetrist • Medical dosimetrist is a member of the radiation oncology team who has knowledge of the overall characteristics and clinical relevance of radiation oncology treatment machines and equipment. • Duties:1. They carefully calculate the dose of radiation to make sure the tumour gets enough radiation. 2. They develop a number of treatment plans that can best destroy the tumour while sparing the normal tissues. Radiation Oncology Nurses • Nurses work with the radiation team to care for patients during the course of treatment. • Duties:1. They help evaluate the patient before treatment begins. 2. They may talk to the patient about potential side effects and their management. Social Workers • Social workers may be available to provide practical help and counseling to patients or members of their families. • Duties :1. They can help a patient and family members cope. 2. They also may help arrange for home health care and other services. Social worker Psychologist Dieticians • Dieticians work with patients to help maintain nutrition. • Duties :1. They monitor patients' weight and nutritional problems. 2. They educate patients. 3. They provide patients with nutritional supplements to improve their nutritional status before, during and after treatment.