An Introduction to Radiation Therapy PDF

An Introduction to Radiation Therapy BME 229 Fall 2024 1 Radiation Therapy (Radiotherapy)  Curative vs. Palliative Treatments Curative care is directed at healing or curing a disease Examples: Taking an antibiotic for an infection, or killing tumor cancer...

An Introduction to Radiation Therapy BME 229 Fall 2024 1 Radiation Therapy (Radiotherapy)  Curative vs. Palliative Treatments Curative care is directed at healing or curing a disease Examples: Taking an antibiotic for an infection, or killing tumor cancer cells with radiotherapy or chemotherapy. Palliative care involves offering treatments that help relieve the symptoms, but does not cure or treat the cause of a disease Examples: Getting a massage for a stiff neck, or getting radiotherapy to reduce pain caused by a bone cancer.  Introduction to Oncology Cancer Uncontrolled cell growth / death Local invasion Distant spread Genetic changes  Malignant vs. Benign Tumors Malignant tumor is cancerous. Malignant tumors can invade and destroy nearby tissue and spread to other parts of the body. Example: Prostate cancer. Benign tumor is not cancerous. Benign tumors may grow larger but do not spread to and/or invade other parts of the body. Example: BPH (benign prostate hyperplasia). An Example – Bone Cancer  Cancer Types Carcinoma – Malignant tumors derived from epithelial tissues that cover internal organs and surfaces of the body Sarcoma – Malignant tumor arising from connective tissue (bone or muscle, etc.) Glioma – Tumours in brain or spine Melanoma – Malignant tumours in skin Lymphoma – Malignant tumors in the lymph nodes or in other lymphoid tissue Leukemia – Cancer of the blood  Canadian Figures (2015) 150,000 new cancer cases per year 45,000 deaths per year 30% of cases fatal – 67% in 1960s – 75% in 1940s Canadian Cancer Statistics 2015 Canadian Cancer Statistics 2015 Canadian Figures (2015) Canadian Cancer Statistics 2015 Main Sites of Malignancy - Males Cases – Prostate – 26% – Lung – 17% – Colorectal – 14% Deaths – Lung – 31% Colorectal cancer is cancer that starts – Colorectal – 12% in either the colon – Prostate – 12% or the rectum. Main Sites of Malignancy - Females Cases – Breast – 31% – Lung – 13% – Colorectal – 12% Deaths – Lung – 25% – Breast – 17% – Colorectal – 12%  Causes Smoking Viruses Sunlight Family History / Genetic facctors Ionizing Radiation Etc.? (food, environmental factors, …)  Screening (Preventive Methods) Find disease early, prior to symptoms More successful treatment Less side effects from treatment Screening (Preventive Methods) Breast – Mammogram Cervix – Pap Smear Colorectal – Fecal/blood test, colonoscopy Prostate – PSA test  Diagnosis (Detection Methods) Patient History Physical examination Biopsy Blood test Imaging Endoscopy Etc.  Treatments Surgery Radiotherapy (Radiation Therapy) Chemotherapy Hormones Immune modulation Antibodies Photodynamic therapy Others (hyperthermia, etc.) Surgery Surgery Colon Cancer  Radiation Therapy (Radiotherapy) Radiation Therapy The use of ionizing radiation to treat or control malignant cells (cancer). Radiotherapy may be used for as a curative, palliative, or adjuvant cancer treatment modality. Curative treatment = Treatment to cure the disease. Palliative treatment = Treatment to alleviate symptoms without curing the disease. For example reducing pain. Adjuvant treatment = Treatment that is added to increase effectiveness of a primary therapy, e.g. radiotherapy after radical surgery or chemotherapy. 22  Radiation Therapy (Radiotherapy) Radiotherapy has also several applications in non-malignant conditions. A few examples: Treatment of Trigeminal Neuralgia, Graves' Ophthalmopathy, Pterygium, etc. The use of radiotherapy in non-malignant conditions is limited partly by concerns about the risk of radiation-induced cancers. Trigeminal Neuralgia = A disorder of the fifth cranial nerve (trigeminal nerve). Resulting in very intense and episodic pain that affects one side of the face. Graves' Ophthalmopathy = An autoimmune inflammatory disorder affecting muscles in the orbit of the eye. Pterygium = A scarring condition of the cornea, caused by exposure to intense sunlight. 23  Radiation Therapy (Radiotherapy) Radiotherapy may be used as the primary cancer treatment therapy. It is also common to combine radiotherapy with other therapy modalities such as surgery, chemotherapy, hormone therapy, and hyperthermia, or some mixture of them. The precise treatment will depend on the tumour type, location, and stage, as well as the general health of the patient. 24  Radiation Therapy (Radiotherapy) Solid Tumors In solid tumors treatment, it is necessary to include a margin of Tumor normal tissue around the tumor to enhance the treatment efficacy and minimize the risk of tumor recurrence. Treatment Margin 25  Radiation Therapy (Radiotherapy) To spare normal tissues (such as skin and intervening and surrounding organs or tissues), shaped radiation beams are aimed from several directions and Tumor angles of exposure to intersect at the tumor, providing a much larger absorbed dose in tumor than in the surrounding, healthy tissue. 26  Radiotherapy Mechanisms of Action Main mechanism of action is cell killing by damaging the DNA of cells (double-strand DNA breaks). The ionizing radiation of high-energy photons, electrons, protons, neutrons, or heavy charged particles. The DNA damage is either direct or indirect ionization of the atoms which make up the DNA chain. One of the major limitations of photon radiotherapy (x-ray and -ray) is that the cells of solid tumors are hypoxic that makes them radioresistive. Much research has been devoted to overcoming this problem including use of treatment fractionation and tumor reoxygenation, use of high pressure oxygen tanks, blood substitutes that carry increased oxygen, hypoxic cell radiosensitizers, etc. Charged particles can cause direct damage to cancer cell DNA through high-LET (linear energy transfer) and have an antitumor effect independent of tumor oxygen supply. 27  Radiotherapy Side Effects The nature and severity of radiotherapy side effects depend on the organs that receive the radiation, the treatment itself (type of radiation, dose, fractionation, concurrent chemotherapy, etc.), and the patient. Two types of side effects: acute (short term) and long term Examples of acute side effects: 1. Damage to the epithelial surfaces (skin, mouth, etc.) 2. Edema (Swelling of soft tissues) 3. Infertility. The gonads (ovaries and testicles) are very sensitive to radiation. Examples of long-term effects: 1. Fibrosis due to a diffused scarring process in the irradiated tissues. 2. Hair loss. Unlike the hair loss seen with chemotherapy, radiation-induced hair loss is more likely to be permanent, but is also more likely to be limited to the area treated by the radiation. 3. Fatigue is among the most common symptoms of radiation therapy, and can range from a few months to a few years. 4. Cancer, in the form of a secondary malignancies caused by radiation! 28  Types of Radiation Therapy The 3 main types of radiotherapy systems are: 1. External beam radiotherapy (EBRT or XBRT) 2. Brachytherapy (or sealed source radiotherapy) 3. Unsealed source radiotherapy The differences relate to the position of the radiation source. External is outside the body, while sealed and unsealed source radiotherapy has radioactive materials delivered internally. Sealed source radiotherapy (brachytherapy) makes use of sealed radioactive sources that are placed inside or next to the cancerous organ/tissue. Examples of sources are: Iridium-192 wires, and Iodine-125 seeds. Brachytherapy is commonly used to treat localized prostate cancer, cervical cancer, etc. Unsealed source radiotherapy makes use of soluble forms of special radioactive substances (radionuclides) which are administered to the body by injection or ingestion. An example: Iodine-131 to treat thyroid cancer. 30  External Beam Radiotherapy Main types of external beam radiotherapy: 1. Conventional (2D) external beam radiotherapy (2DXRT) 2. 3-Dimensional conformal radiotherapy (3DCRT) 3. Intensity-modulated radiotherapy (IMRT) 4. Image-guided radiotherapy (IGRT) Treatment planning and simulation: A critical step before delivering the treatment. The aim of the treatment planning and simulation is to accurately target or localize the tumor to be treated, and to specify the number, directions, dosages, and shapes of the beams. 31 Treatment Planning and Simulation 32  Conventional (2D) External Beam Radiotherapy (2DXRT) Conventional external beam radiotherapy (2DXRT) is delivered via ionizing beams using linear accelerator machines (LINAC). LINAC generates high energy X-ray or electron beams. 2DXRT mainly consists of a uniform beam of radiation delivered to the patient from several directions: often front or back, and both sides. Conventional refers to the way the treatment is planned or simulated, i.e. using 2D X-ray imaging. 33  3-Dimensional Conformal Radiotherapy (3DCRT) The main difference between the 2DXRT and the 3DCRT is that the latter makes use of specialized CT and/or MRI scanners and planning softwares to achieve 3D treatment planning. This leads to a more accurate and effective treatment of the tumor volume with reduced unwanted exposure to their surrounding normal tissue. 34 Intensity-Modulated Radiotherapy (IMRT) Intensity-modulated radiation therapy (IMRT) is an advanced version of the 3DCRT. It utilizes an adaptive dosage scheme in which the maximum dosage is delivered to the tumor while the surrounding normal tissues receive a minimal dosage. IMRT also improves the ability to conform the treatment volume to complex tumor shapes, for example when the tumor is wrapped around a vulnerable structure such as the spinal cord or a major organ or blood vessel. It further improves the treatment efficacy and reduces side effects. 35 Intensity-Modulated Radiotherapy (IMRT) Treatment Planning 36 Intensity-Modulated Radiotherapy (IMRT) Multi-leaf Collimator Made of individual "leaves" of a high atomic numbered material, usually Tungsten. 37  Image-Guided Radiotherapy (IGRT) Latest technology in external beam radiotherapy. It utilizes intraoperative imaging (X-ray, CT or MRI) and treatment monitoring to further enhance the treatment efficacy and safety for a wide range of tumors treatment. Real time or quasi real time imaging. Registration of intraoperative imaging with 3D preoperative imaging dataset (e.g. during treatment planning) toward more accurate treatment monitoring and control. 38  Gamma Knife Gamma knife is a special external beam radiotherapy device used to treat brain tumors with a high and focused dose of radiation therapy in one treatment session. Radiation dose in a range of 10 to 150 Gy. The device contains a large number of cobalt-60 sources (e.g. 201 of them), each placed inside a spherical array in a heavily shielded assembly (beta decay). 40  Gamma Knife Brain tumours Arteriovenous malformations (AVMs) Other neurological conditions Using the stereotactic radiosurgery technique, the device aims high-dose Gamma radiation to a sharply focused target point in the patient's brain. 41 Example – Brachytherapy for Prostate Cancer Under Transrectal Ultrasound Guidance Iridium-192 seeds green iso- dose line: prescription dose 144 Gy seed: 0.435 mCi Example - Brachytherapy