Cervical Cancer/Radiation Therapy Flashcards
What do all types of radiation have in common?
They all use high energy waves to kill cancer cells
Why is radiation more harmful to cancer cells than to normal, healthy cells?
Because normal cells are not dividing and they are better able to repaire themselves.
What is the difference between external radiation and internal radiation treatment?
EXTERNAL: aim an x-ray machine at the area with cancer and deliver radiation from outside the body.
INTERNAL: use radioactivity and place it near to or into a tumor within the body to administer direct, very localized therapy
What tools do the radiation ocologists use to ensure that they administer external beam radiation accurately?
- use a marker to mark the spot
- Mould to position your legs (prostate cancer) to ensure you were in the same position each time
- Mask to put over the patients head
Radioactive elements emit a natural form of x-rays known as _____________
Gamma Rays.
What international term is used used to measure the radiation dose?
Gray (Gy)
How does radiation therapy work?
inflicts damage on the DNA of the cancer cells by interacting with the cells water to produce free radicals. These free radicals are highly reactive, and cause breakdown of DNA strands
ruining their ability to reproduce, thus shrinking the tumor.
Cells vary in their sensitivity to radiation treatment. Typically, which cancers are most highly radiosensitive? And after these, which are considered FAIRLY radiosensitive?
- rapidly dividing cells (both cancerous and healthy) are most sensitive to radiation therapy (Lymphoma, leukemia, seminoma, and dsygerminoma).
- oropharyngeal, glottis, bladder, skin, cervical epithelia, adenocarcinomas of the alimentary tract
At what phase(s) of the cell cycle are cells most sensitive to radiation therapy?
Mitosis (when cell division occurs) andG2 phase (when protein and RNA synthesis occur)
What types of cancer are fairly low in radiosensitivity?
-breast, salivary gland tumors, hepatomas, renal cancer, pancreatic cancer, chondrosarcoma, osteogenic sarcoma
What is a Vero Machine?
All-in-one radiation/imaging/patient positioning system that focuses the radiation dose on the central target (tumour) while sparing surrounding healthy tissues and organs. Able to compensate positioning to move with breathing and heart rate so that administration is exactly on target, minimizing damage to surrounding healthy tissue
When are cells most radioresistant?
During the S phase (Synthesis) when DNA is duplicated.
Would you expect a large tumor to be more or less radiosensitive? Why?
The presence of oxygen enhances radiation damage by interfering with the repair process. Large tumors are radioresistant because they have a greater volume of hypoxic tissue.
How do you determine the therapeutic ratio of radiation therapy?
overlap of normal tissue tolerance dose and dose required to destroy the tumor. This is improved by best targetting the tumor while sparing normal tissue
What are the 4 Rs or radiobiology?
Repair (ability of cells to recover from sublethal damage)
Redistribution (distribute radiation at different phases of the cell cycle for maximum kill)
Repopulation (regeneration of cells after radiation damage)
Reoxygenation (as the tumor shrinks, it becomes more oxygenated, increasing radiosensitivity)
