Radiation Therapy PDF

RADIATION THERAPY Prophylactic - is a type of radiation therapy CLUSTER 5 used to prevent the spread of cancer from one...

RADIATION THERAPY Prophylactic - is a type of radiation therapy CLUSTER 5 used to prevent the spread of cancer from one part of the body to another AIMS OF RADIATION THERAPY Palliative Intent- is the use of radiation to a specific area to shrink a tumor, and slow down To kill the malignant cell in a tumor, or to tumor growth. or to reduce or relieve Render them permanently incapable of further cell symptoms such as pain and bleeding. division Without producing excessive damage to the TYPES OF CANCER TREATMENT surrounding normal tissues To deliver a precise Cancericidal dose 1. SURGERY - Branch of medicine that deals with the diagnosis RADIATION ONCOLOGY and treatment of injury, deformity, and disease by natural and instrumental means. A clinical and scientific endeavor devoted to the - It comes from the Greek word "cheirourgen", management of patients with cancer and any made up of "cheir" Chand), and "ergo" (to work). other disease by lionizing radiation alone or Literally means to work with the hand. Thus, combined with other modalities. investigation of surgery can be defined as those manual the biologic and physical basis of radiation procedures used in the management of injuries therapy, and training of professionals in the field. and disease RADIATION THERAPY 2. CHEMOTHERAPY - It works by Interrupting cell growth and division in A clinical specialty dealing with the use of ionizing general. Different agents interact with the cell and radiation in the treatment of patients with its DNA in various ways. While the particular form malignant neoplasia can occasionally with benign of chemotherapy that is administered is selected condition): is the treatment of disease, primarily for its activity against a specific cancer, most malignant tumors, using electromagnetic and drugs also interrupt normal cell growth and particle radiation. division - The Human body processes and excretes all RADIATION ONCOLOGY TEAM drugs from the liver or the kidneys. Therefore, when a patient has liver or kidney damage, giving 1. Radiation Oncologist - clinical evaluation. chemotherapy becomes dangerous. Therapeutic decision, target volume localization, simulation & verification of treatment plan, ADMINISTRATION periodic evaluation. follow-up evaluation. Oral 2. Medical Physicist - ensure the accurate Intravenous delivery of radiation therapy, treatment planning Intramuscular and quality assurance Intrathecal 3. Medical dosimetrist - (dose calculation, deliver Intraperitoneal safe doses to px) beam data computerization, analysis of treatment plan, selection of treatment MAJOR CLASSES OF CHEMOTHERAPY DRUGS plan, patient contour, dose calculation. Alkylating agents 4. The radiation therapist - target volume Antimetabolites localization, treatment planning simulation, Antracyclines treatment of a patient, localization films, Camptothecins positioning of patients making of blocks (photon Taxanes platinums and electrons) COMMON SIDE EFFECTS OF CHEMOTHERAPY TYPES OF TREATMENT INTENT Side effects of chemotherapy depend on the type of drugs the amounts taken, and the length of CURATIVE/RADICAL INTENT treatment. 1. Adjuvant - delivered After surgery to kill any remaining cancer cells and lower the risk of Alopecia cancer recurrence. Stomatitis 2. Neoadjuvant - given before surgery to shrink a Dysphagia tumor or stop disease spread optimizing the Nausea and Vomiting success of the main treatment and making it Constipation less invasive. Diarrhea 1 Skin Reactions Effects on Bone Marrow CELL ADAPTATION (Anemia, Neutropenia. Nausea and Vomiting Neoplasia - abnormal proliferation Thrombocytopenia) Aplasia - organ or part of organ missing Infertility Metaplasia - conversion in cell type Dysplasia- change in cell or tissue (badly developed) 3. BIOLOGIC THERAPY (Immunotherapy) Anaplasia - structural differentiation loss (retro) - It uses the body's immune system to fight cancer or to lessen the side effects of some Hypoplasia - congenital below-average number of cancer treatments. cells - Cancer Immunotherapy refers to a diverse Desmoplasia - connective tissue growth (scar) set of therapeutic strategies designed to induce the patient's immune system to fight 2 TYPES OF NEOPLASM ACCORDING TO the tumor ACTIVITY Contemporary methods for generating an immune Benign Tumor – non-cancerous. non-progressive response against tumors include the use of disease and does not spread. interferons and other cytokines to induce an immune Malignant Tumor – has the ability to spread response in renal cell carcinoma and melanoma patients. beyond the site of origin. Tumors may invade the neighboring tissue to distant sites forming 4. HORMONE THERAPY secondary growth known as metastases. (either increase or limit the presence of hormones), - Hormones are chemicals that act naturally 3 MAJOR SUBTYPES OF CANCER produced by the organs making up the body's endocrine system. These chemicals travel Carcinoma throughout the body via bloodstream (directlv – arise from epithelial tissue released to the bloodstream, coordinating the Sarcoma functions of various organs from head to toe) – arises from the connective and supportive - Researchers have determined that some cancers are "fueled" by hormones, and may tissues (Leiomyoma, Rhabdomyoma) rely on them to grow. In those cases blocking Lymphoma the reaction of these hormones could stop the – includes cancers that involve blood-forming cancer from growing. tissue - The growth of some cancers can be inhibited enlargement of the lymph nodes by providing or blocking certain hormones. invasion of the spleen and bone marrow Common examples of hormone-sensitive tumors include certain tvpes of breast and overproduction of immature white cells. prostate cancers. Removing or blocking estrogen or testosterone is often an imnortant 3 PATHWAYS OF MALIGNANT NEOPLASM additional treatment Seeding (Diffused Spread) 5. CRYOTHERAPY – occurs when neoplasm invade a natural body cavity. Lymphatic Spread WORLDS TOP 3 KILLERS – major metastatic site of carcinomas, especially Cardiovascular diseases- 29% those of the lung and breast. Infectious diseases- 16.2% Hematogenous Spread Cancer- 12.6% – wherein tumor cells invade and penetrate blood vessels and are released as neoplastic emboli CANCER into the circulation. is a disease process that involves an unregulated, uncontrolled replication of cells the cells do not know when to stop dividing. dedifferentiated 2  REMISSION DIAGNOSIS a period of time where the cancer is responding to treatment or is under control. PET Scan COMPLETE REMISSION - Utilizing Radiopharmaceuticals commonly PARTIAL REMISSION Fluorine-18(fluorodeoxyglucose) - does not completely disappears. Biopsy medical removal of tissue from a living subject RECURRENCE to determine the presence or extent of a disease. examined under a microscope by a pathologist. period of time when a cancer returns after a -for TYPING of tissue growth period of remission. SECOND PRIMARY CANCER – term for the TYPES OF BIOPSY recurrent cancer Excisional Biopsy – an entire lump or suspicious area is removed. 3 TYPES OF RECURRENCE Incisional Biopsy 1. LOCAL RECURRENCE - same place where it was – when only a sample of tissue is removed with found, or very close by. preservation of the histological architecture of the 2. REGIONAL RECURRENCE – Occurs in the lymph tissue’s cells. nodes and tissue located in the vicinity of the patients – Also called “core biopsy”. local cancer. Fine Needle Aspiration (FNA) 3. DISTANT RECURRENCE –to areas farther away – uses a fine needle and a syringe to sample fluid from where cancer was first located. such as from a breast cyst. Core Needle Biopsy 6 HALLMARKS OF CANCER – a procedure that removes small but solid samples of tissue using a hollow “core” needle. Immortality – Telomeres CLASSIFICATION OF TUMOR DIAGNOSIS – Hayflick limit – the limit of a cell on further division Grading – 60 – 70 doubling – assessment of neoplasm aggressiveness – HeLa Cells – Henrieta Lacks 1951 Staging Produce “Go” signals – Proto-oncogenes – assessment of tumor size, affected node and Override “stop” signal metastasis – Tumour suppressor genes Avoidance of cell death Roman Numeral Staging – Apoptosis – Stage I: Early localized tumor, often in site, usually Loss of positive signal without lymph nodes or metastatic involvement Induction of negative signal – Stage II: Primary tumor has involved underlying Angiogenesis (neovascularization) tissues but is still localized Metastasis – Stage III: Primary tumor has spread to regional – Process of “Diapedesis” – entry of cell to vessel lymph nodes wall – Stage IV: Primary tumor has spread beyond anatomical bounds of organ to regional lymph nodes, RISK FACTORS metastatic potential is very high. External Factors TNM SYSTEM Exposure to chemicals Viruses The TNM system is the one used most often in radiation staging cancer. It gives three key pieces of Internal factor information. Hormones T describes the size of the tumor, and whether the genetic mutation cancer has spread to nearby tissues and organs. disorders of the immune system 3  N describes how far the cancer has spread to nearby lymph nodes. M shows whether the cancer has spread to the other organs of the body. CLASSIFICATION OF TUMOR DIAGNOSIS Stage IA - T1 N0 M0 Stage IB - T2 N0 M0 Stage IIA - T1 N1 M0 Stage IIB - T2 N1 M0; T3 N0 M0 Stage IIIA - T3 N1 M0; T1 N2 M0; T2 N2 M0; T3 N2 M0 RADIOBIOLOGY Stage IIIB - T4 N0 M0; T4 N1 M0; T4 N2 M0; T1 N3 LAW OF BERGONI’E AND TRIBONDEAU M0; T2 N3 M0; T3N3M0; T4 N3 M0 Stage IV - Any T, Any N, M1 PHYSICS The higher the energy, the more deeply the radiation can penetrate (get into) the tissues. The way a certain type of radiation behaves is important in planning radiation treatments. Cell Cycle(Mitosis) G1 phase TYPES OF RADIATION - The cell starts making more proteins to get ready to divide. Electromagnetic type S phase Proton beams are charged parts of atoms that - the chromosomes that contain the genetic cause little damage to tissues they pass through code (DNA) are copied but are very good at killing cells at the end of their G2 phase path - just before the cell starts splitting into 2 cells. SKIN SPARRING EFFECT M phase (mitosis) - MV photons do not reach maximum dose at - cell splits into 2 new cells that are exactlythe the surface/skin but build-up to a maximum same. dose. This effect is referred to as skin sparing and is desirable for most photon treatments. Particulate type Electron beams or particle beams are also produced by a linear accelerator. These are used for tumors close to a body surface since they do not go deeply into tissues Neutrons beam can cause more DNA damage than photons, (LET= 50 keV/um) the effects on normal tissue may be more severe. beams must be aimed carefully and normal tissue Protected Alpha particle Direct and Indirect effect Alpha particle- has a large LET value but is Direct effect virtually non-penetrating and is essentially - direct interaction and inactivation of target useless as a therapeutic tool. molecule. Indirect effect - Ionization of other molecules and produces highly reactive free radical which then interacts with the DNA. 4 Types of chromosome aberration HISTORICAL PERSPECTIVE Lethal to cell - dicentric ring, centric ring and anaphase January 29, 1896 - Dr. Emil H. Grubbe - first bridge therapeutic application of x ray with breast cancer Non lethal patient. - reciprocal translocation and small deletions PieRre and Marie Curie discovered Polonium and Radium in 1898. Radiolysis of Water January 1902 - The first reported curative The principal radiation interaction of the body treatment using ionizing radiation was performed Forms free radical by Dr. Clarence E. Skinner, considered cure in - Hydroperoxyl (HO2*) 1909 - Hydrogen peroxide (H2O2) RADIATION THERAPY RELATED TERMS LET and RBE LET – Linear energy transfer Treated Volume (TV) - Has a unit of keV/μm volume within an isodose surface considered - Another method of expressing radiation appropriate to achieve the purpose of treatment. quality - Diagnostic x-ray has an LET of 3keV/μm Irradiated Volume RBE – Relative Biologic Effectiveness is the volume of tissue that receives a dose - As the LET increases so as the biologic effect considered significant in relation to tissue - Diagnostic x-ray has an RBE of 1 tolerance. Gross Tumor Volume (GTV) is the gross palpable or visible/ demonstrable extent and location of malignant growth. Clinical Target Volume (CTV) is a tissue volume that contains a demonstrable GTV and subclinical microscopic malignant disease that must be eliminated. Planning Target Volume (PTV) contains CTV with anisotropic margin for Possible uncertainties consider organs at risk (OAR) Dose Response Curve Dose-effect Relationship - Linear - Non- Linear - Threshold- (deterministic) - Non- Threshold- (stochastic) 5  - ratio of dose in tissue to dose in air OTHER RELATED TERMS SAR - scatter air ratio Isocenter - determines the scattered dose component in - the intersection of axis of gantry rotation & radiation therapy axis of collimator rotation TPR SSD - tissue phantom ratio - from source to Tx target - ratio of dose rate a given depth in tissue to SAD the dose rate at the same source to point - distance from source to isocenter distance, but at a reference depth - Cobalt 60: SAD of 80 cm TMR - Linear Accelerator: SAD of 100 cm - tissue maximum ratio Dose rate - a special case of TPR in which the reference - measured at the isocenter depth is defined as a fixed dmax for allfield sizes. SPR - scatter phantom ratio SMR - scatter maximum ratio OTHER NOMENCLATURE TAR-tissue air ratio, ratio of dose in tissue to dose in air. SAR-scatter air ratio: determines the scattered dose component in radiation therapy DMAX TPR-tissue phantom ratio: ratio of dose rate at a - the depth at which electronic equilibrium given depth in tissue to the dose rate at the same occurs for photon beams. source to point distance, but at a reference depth - the point where dose reaches its maximum TMR-tissue maximum ratio: a special case of TPR value. in which the reference depth is defined as a fixed - *Mainly depends on the energy of the beam Dmax for all field sizes. 3 Type of Radiation therapy 1 External Beam Radiation Therapy Also called teletherapy treatment, or long distance The patient lies underneath a machine that emits radiation or generates a beam of x- rays. Radiation therapy technique for which source of radiation is at some distance from patient Delivery of radiation to a patient from a unit such as a linear accelerator in which the radiation enters the patient from the external surface of the body. 2. Brachytherapy Percent Depth Dose (PDD) "Brachytherapy is a method of treatment in which - the ratio expressed as a percentage, of sealed radioactive sources are used to deliver absorbed dose at a given depth to absorbed radiation at a short distance by Interstitial, dose at DMAX Intracavitary, or surface application With this mode of therapy, a high radiation dose can be delivered locally to the tumor with rapid dose fall off in the surrounding normal tissue. "In the past, Penumbra brachytherapy was carried out mostly with radium - located in the area of beam edges where or radon sources. dose rate falls-off rapidly Currently, use of artificially produced radionuclides such as 137Cs, 192Ir. 198 Au. 125I and 103 Pd is TAR more common. - tissue air ratio 6  - Indicates shielding TYPES OF TREATMENT FOR LINEAR - Can be used as reference image for tx ACCELERATOR verification X-ray or Photon - for deep therapy (underlying CT SIMULATOR tumors) - Is a CT scanner that include software Electrons - for superficial therapy (superficial manipulation to emulate a BEV similar to that lesions) of a simulator - A CT simulator introduces concept of virtual Radiation Therapy Process simulation 1. Clinical evaluation 2. Consultation 3. Treatment planning 4. Simulation 5. Treatment 6. Tx evaluation & follow-up Treatment Planning - determining the volume of tissue that needs to be encompassed within the radiation field Single field- the entire tumor dose is delivered through only one treatment port of field; an IMMOBILIZATION DEVICES example is the treatment of skin cancer. Thermoplastic Mask Opposing ports- the tumor dose is the result of - takes up its shape when heated to immobilize contributions from fields I and II. certain patient movement. Multifield- employs the use of three or more fields to deliver the tumor dose. Rotational field (Arc) - the source of radiation rotates around the patient until the dose has been delivered. Wedge field- to alter the primary beam and obtain the desired isodose distribution. Shaped field- using shaper blocks Alpha Cradle SIMULATOR - Made of two chemicals that can be mixed together to form a styrofoam-like material that Major steps in target localization and field design: may take the shape of the patient 1. Acquisition of patient data 2. Localization of target and adjacent sturctures OTHER ACCESSORY MATERIALS: 3. Definition and marking of patient 4. Design of tx fields Custom blocks- made of cerrobend; frequently 5. Transfer of data to tx planning system used to create unique field shapes 6. Production of image for tx verification Bolus- tissue-equivalent material -removes skin sparring effect Diagnostic tools for localizing targets Palpation X ray Ultrasound MRI PET/SPECT CT scan Simulator radiograph SIMULATORS FILM - Shows relevant anatomy - Indicates field placement and size 7  Wedge filters - placed in the path of the beam to ORGAN TOLERANCE DOSE TO RADIATION attenuate and modify the isodose distribution in a specially tilted configuration Compensators- evens out irregular skin surface contours, while retaining skin sparing advantage. Beam spoiler- made of lucite, placed in the path of the beam to reduce the depth of the maximum radiation dose BUILT-IN ACCESSORY RADIATION DOSE Flattening filters - spatial distribution of the natural beam is Dose Unit altered by reducing central exposure rate Absorbed dose refers to the amount of energy relative to the peripheral deposited per unit mass - Used in LINAC Measured in rad New SI unit cGy is used for radiation therapy 1 J/kg = 1 Gy = 100 rad 1 rad = 1 cGy DOSE DETERMINATION INSTRUMENTS Ionization chambers 1. Thimble ionization chamber (cylindrical ionization chamber) 2. Parallel plate ionization chamber For electron beam dosimetry w/