Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Fundamentals 3- Heme > Radiation Oncology > Flashcards

Radiation Oncology Flashcards

1
Q

List the two general uses of radiation in cancer treatment.

A
  1. Local treatment to target the area of known disease plus and area of normal tissue and lymphatics for that area
  2. Systemic therapy where the isotope is metabolized and concentrated in a particular tissue or linked to Ab which concentrates in tumor cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How has the overall incidence rate of cancer in women and men changed from 1995?
How has the mortality rate changed?

A

It has stabilized for me and slightly increased for women.

The mortality rate has continued to decrease for both

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How does incidence of cancer rate differ amongst race?

A

African american men and women have a 40% higher incidence and 20% death rate higher than Whites for lung, colorectal, prostate and breast cancers. The other ethnicities have a slightly lower incidence and death rate, except they have a higher rate for stomach liver and cervical cancers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the three major treatments for cancer?

Which act locally and which act systemically?

A
  1. Surgery- local excision of the tumor, marginal tissue and lymphatics for the area
  2. Radiation- local or systemic (isotopes metabolize and concentrate in particular tissue or linked to an Ab that targets tumor cells preferentially to normal cells)
  3. Chemo- systemic where the drugs are administered to target tumor cells throughout the body
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What type of radiation is used for most treatments of cancer?

A

Ionizing radiation in which the radiation is of sufficient energy to eject one or more electrons from the orbit of the target atom or molecule.
This releases enough energy to break strong chemical bonds (33eV)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the two types of ionizing radiation?

A
  1. electromagnetic (x-ray, gamma ray, photons)

2. Particulate (electrons, protons, neutrons, a-particles, heavily charged ions)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How are the energies used in modern radiation therapy quantified?
What are the three voltage ranges and which do most treatments work in?
What are the two major treatment strategies used today?

A

othovoltage - 150 to 500kV
supervoltage- 500 to 1000kV

megavoltage greater than a MV (ex. Cobalt 1.25MV or Linear Acceleration (6-18 MV)

Modern therapy generally works in the megavoltage range with Linear Acceleration or Cobalt.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is a roentgen, rad and gray (Gy)?

A

Roentgen is unit of EXPOSURE related to the ability of the x-ray to ionize air
Rad is the unit of ABSORPTION corresponding to 100ergs/g
Gray is the current unit to measure radiation exposure and is equal to 1J/kg

1cGy = 1 rad

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the difference between “directly ionizing” and “indirectly ionizing”?

A

Charged particles like electrons, protons, neutrons etc are directly ionizing by disrupting the atomic structure of the absorber.

Electromagnetic radiation is indirectly acting because x-rays and gamma rays do not directly produce biological or chemical damage but rather give up their energy to the absorber which produces charged particles.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the most important site of action in the treatment of cancer?
What is the most clinically important type of damage?

A

The most important site of action is the DNA within the cell.
Photons interact with atoms to produce ion radicals which in turn produce free radicals which damage DNA.
Double strand breaks are the most clinically important type of damage by ionizing radiation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What cells are targeted by ionizing radiation?

A

All the cells in the area where the radiation is sent. This could include healthy and cancerous cells.
Normal cells have good DNA repair mechanisms and thus are damaged less than the cancer cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

List the time course for indirectly acting ionizing radiation. Not where the DNA insult occurs and where the DNA injury occurs.

A
  1. X-ray photon (10^-15s)
  2. fast electron (10^-15s)
  3. ion radical(10^-9 s)
  4. free radical (insult) (10^-9s)
  5. DNA break (injury) (10^-5s)
  6. biological effects (hours to years)
  7. cell killed and transformation occurs (hours to years)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the three possible outcomes of DNA damage after ionizing radiation?

A
  1. DNA damage is so bad the cell undergoes apoptosis
  2. DNA damage does NOT kill the cell but damage is irreparable resulting in chromosomal aberration expressed when the cells divide(LOF).
  3. DNA damage is in germ cells and the damage is inherited in offspring
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the relationship between damage to cells and radiation dose?

A

As the radiation dose increases, the probability of cell damage increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

The ideal radiation treatment would be greater than the doese needed for ___________ but less than the dose _______________________.

A

greater than the dose needed for local control but less than the dose causing major complications

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What four things can modify the response to radiation?

4 R’s

A
  1. Cell cycle “reassortment”
  2. type of radiation/ Repopulation
  3. oxygen enhancement (reoxygenation)
  4. fractionation (repair)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is meant by cell cycle reassortment?

What stages of the cell cycle are most sensitive to radiation? Least? Moderate?

A

Radiation can redistribute cells to different parts of the cell cycle.
Cells in M phase and G2 are most sensitive to radiation because the cells are growing and preparing to divide.
Cells are least sensitive to radiation in late S phase(DNA synthesis)
Cells are moderately sensitive to radiation in G1 and early S

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Drugs which increase the portion of cells in ____ and _____ phases will have increased radiation effects.

A

M and G2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the three possible effects of radiation on any individual cell?

A
  1. no effect- no damage in a critical site or target
  2. Cell death if enough damage occurs at a critical site
  3. recovery due to repair of sublethal damage
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What does the dose-response survival curve look like for densely ionizing radiation?

A

It is a straight line from the origin.
Survival is an exponential function of dose.
Higher the dose, less survival.
Log Kills

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What does the dose-response survival curve look like for sparsely ionizing radiation (x-ray or gamma)?

A

Initial linear slope follwed by a shoulder.

The curve becomes straighter (log kills) at high enough doses

22
Q

Which would be more likely to elicit DNA damage, densely ionizing radiation or sparsely ionizing radiation? Why?

A

Densely because the ions are clustered around the DNA causing strand breaks.
Sparsely ionizing radiation has electrons set in motion by photons and is more spread out.

23
Q

What is meant by oxygenation in regard to ionizing radiation?

A

Cells are more sensitive to radiation when they are in oxygen-rich environments. They are LESS sensitive when they are hypoxic.
Oxygen Enhancement Ratio.

24
Q

Would a larger or smaller tumor require more radiation? Why?

What treatment technique can be used to improve outcomes for larger tumors?

A

Larger because they outgrow their blood supply and are hypoxic in the central area (necrosis). Radiation kills the periphery, but can’t get to the center.
Fractionation allows for radiation to kill the oxygen-rich periphery, then reoxygenation of the tumor, followed by more radiation, etc.

25
Q

What is fractionation?

A

Providing radiation in a single dose (fraction) gives a greater cell kill than the same dose of radiation spread out over multiple smaller doses. However, sometimes spreading the dose out yields better results because less normal cells are killed.

Balance between killing cancer cells and allowing survival of normal cells (especially because radiation repair is more efficient in normal cells than cancer cells)

26
Q

What is standard fractionation?
Hyperfractionation?
Accelerated fractionation?

A

Standard- once a day, five days a week
Hyperfractionation- decreases dose per fraction but increases total dose delivered
Accelerated fractionation- decreased total treatment time without decreasing the number of fractions or total dose or dose/fraction.

27
Q

What is the benefit of hyperfractionation?

A

It decreases the dose per fraction but increases the total dose delivered.
This increases killing of tumor cells while normal cells are still able to repair damage

28
Q

What is the benefit of accelerated fractionation?

A

It is when the treatment time is shortened with little to no change in fraction, dose/fraction, total dose.

This gives less time for regeneration of tumor cells during treatment

29
Q

What is accelerated hyperfractionation?

A

It is a combo of accelerated fractionation (shorted treatment time) and hyperfractionation (increased number of fractions but less dose per fraction)

30
Q

What is the difference between radical and adjunctive radiation?
What are 2 examples of tumors that would require radical treatment?
What are 2 examples of tumors that would require adjunctive radiation?

A

Radical is just radiation. (Lung, Anal, PRostate)
Adjunctive is surgical removal of tumor and lower dose radiation to kill cells that may have been missed. (Pancreas, Sarcoma)

31
Q

What 4 things determine the side effecs of radiation therapy?

A
  1. site of body being treated
  2. volume of tissue irradiated
  3. total dose delivered
  4. Dose/Fraction
32
Q

When do acute side effects from radiation occur?
What type of tissue demonstrate acute side effects?
What are the effects a result of?
Can the tissue be repaired?

A

They occur day to weeks after radiation in tissue with rapid cell turnover.
The effects are a result of large number of cell death.
This tissue can be repaired.

33
Q

When do late effects of radiation occur?
What type of tissue demonstrate the late side effects?
What are the effects a result of?
Can the tissue be repaired?

A

They occur months or years after radiation in slowly proliferating tissue.
They occur because of vascular damage or parenchymal cell loss.
This tissue cannot ever be completely repaired.

34
Q

What is TD5/5?

What is TD50/5?

A
  1. minimal tolerance dose- no more than 5% severe complication rate in 5 years of treament.
  2. maximal tolerance dose- 50% severe complications in 5 years of treatment
35
Q

What organ can tolerate radiation the least? (lowest TD5/5)

A

Fetus- 2Gy
Lung-15 Gy
Kindey- 20 Gy

36
Q

What organs can tolerate radiation the best? (highest TD5/5 and TD50/5)

A

Brain- 50Gy
Spinal cord-45 Gy
Intestines -45 Gy
Stomach-45 Gy

37
Q

What are the five steps in developing a plan for radiation treatment?

A
  1. Identify if you are going to treat
  2. Simulation (CT scan with immobilization)
  3. Target organ/ at risk tissue
  4. Planning
  5. Delivery
38
Q

What are the two main methods of delivery of radiation?

A
  1. Teletherapy- external beam irradiation

2. Brachytherapy- radiation source placed in the body

39
Q

What are the two main teletherapy units used today? How do they work?

A
  1. Linear Accelerator- radiation is generated with electricity. Electrons are accelerated then rapidly decelerated in target material to produce X-ray
  2. Cobalt unit
40
Q

What are the advantages of using a linear accelerator?

A

Advantages:

  1. absence of radiation when the machine is turned off
  2. multiple strengths of photons and electrons in the same machine
  3. 4-25MV of radiation
41
Q

What are the advantages and disadvantages of using Cobalt unit for teletherapy?

A

Advantages:
1. easy to maintain

Disadvantages:

  1. low energy radiation (1.25MV)
  2. periodic replacement of Cobalt due to radioactive decay
  3. emits radiation when not in use
42
Q

How can external beam irradiation be used to treat tumors inside the body rather than on the surface?

A

Multiple lasers from different directions are aimed to intersect at the site of the largest volume of tumor.
(simple field- two opposing beams)
(complex field - 6 opposing beams)

43
Q

What is Intensity Modulated Radiation Therapy (IMRT)?

A

A technique that maximizes dose to the target volume and minimizes dose to surrounding normal tissue

44
Q

What is IGRT (image guided radiation therapy)?

A

A technique that uses imaging to track the movement of the tumor during treatment

45
Q

What is Brachytherapy?

A

When a radiation source is placed in the body (as opposed to external beam radiation)
The implanted chip emits radiation to the surrounding tissues and falls off at 1/distance^2

46
Q

What is the advantage of brachytherapy?

What is the most common site for brachytherapy?

A

the ability to deliver a very high dose of radiation the tumor with relative sparing of the adjacent normal tissue.
The most common site of brachytherapy is GYN malignancies like cervical cancer

47
Q

What are the three main factors to consider when making treatment decisions?

A
  1. Histopathology (site of tumor and size)
  2. Stage (extent of spread)
  3. Goal of treatment (palliative vs. curative)
48
Q

What are the most sensitive cells to radiation?

A

Rapidly dividing and undifferentiated cells. It is good for leukemia and lymphoma, multiple myeloma and seminoma.

49
Q

What kind of tumor would elicit curative radiation?

What would elicit palliative radiation?

A

Curative- local or local/regionalized tumors

Palliative- widespread/metastatic with symptomatic disease

50
Q

Compare a palliative radiation regimen to curative.

A

Palliative doses of radiation are higher dose/fraction but a lower total dose.

Fundamentals 3- Heme (19 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions