Topic 1: Principles of Treatment using radiotherapy

By the end of this unit you will have learned, what radiotherapy is, terms used, types, indications and  side effects  on cancer patients

Definitions

Radiation therapy is a type of cancer treatment that uses beams of intense energy to kill cancer cells.

Radiation therapy most often uses X-rays, but protons or other types of energy also can be used.

 

Excitation -an electron in an atom or molecule is raised to a higher energy level without being ejected

Ionization -an electron in an atom or molecule is given enough energy to be ejected.

in living material, this releases enough energy locally to break biological bonds

 

·       electrons: small negatively charged particles can be accelerated to almost the speed of light.

·       protons: positively charged particles , mass ~ 2000 times greater than electron

·       alpha particle: nucleus of helium atom = 2 protons + 2 neutrons ( ie decay of radium-226 to radon-222)

·       heavy charged ions: nuclei of elements C, Ne, Argon, etc.

 

radiation damages

are of three types:

·       Lethal: leads irrevocably to cell death

·       Potentially lethal: radiation damage which can be modified by artificial post radiation conditions (ie balanced salt solution) to allow repair.

·       Sublethal: in normal conditions, can be repaired in a few hours. Its repair is shown by increased survival when a dose of radiation is split into 2 fractions separated by a time interval.

 

Indications

1.     As the only (primary) treatment for cancer

2.     Before surgery, to shrink a cancerous tumor (neoadjuvant therapy)

3.     After surgery, to stop the growth of any remaining cancer cells (adjuvant therapy)

4.     In combination with other treatments, such as chemotherapy, to destroy cancer cells

5.     In advanced cancer to alleviate symptoms caused by the cancer