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14 Onco > Principles of Radiotherapy > Flashcards

Principles of Radiotherapy Flashcards

1
Q

principles of radiation therapy

A
  • minimize therapy
  • minimize negative impact on quality of life
  • improve quality of life
  • maximize impact on quality of life (cure or remission)
  • improve outcomes
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2
Q

we do not want to overtreat patient because of ___

A

toxicity, time, and costs

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3
Q

function of improving the quality of life

A
  • for patients that need palliation

- organ and function preservation

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4
Q

2 types of radiation

A

particulate radiation and electromagnetic radiation

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5
Q

type of radiation dictates ___

A

how the radiation is used for treatment

how to protect the radiation workers

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6
Q

2 subtypes of particulate radiation

A

alpha: can be stopped by a thin piece of paper
beta: need aluminum shielding to protect workers

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7
Q

electromagnetic radiation used for treatment

A 
gamma radiation (needs a thick concrete block for protection)
- shorter wavelength, higher frequency, higher energy
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8
Q

radiations that come from machines

A
  • linea accelerator (LINAC) !!!
  • tomotherapy
  • halcyon
  • cyberknife
  • proton machines
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9
Q

types of radioactive materials

A
  • cobalt: ebrt, bachytherapy, gamma knife
  • iridium: brachy (gyne)
  • iodine: brachy (prostate)
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10
Q

classification of radiotherapy according to treatment type

A
  • external beam radiotherapy

- brachytherapy

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11
Q

most common machine used for radiotherapy

A

linear accelerator (linac)

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12
Q

principle of linac

A
  • can produce high energy photons (electromagnetic type of radiation, for deeper tumors)
  • electrons (particulate type, for superficial tumors)
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13
Q

benefits of linac

A
  • more uniform beam characteristics
  • more precise field shaping
  • more precise delivery
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14
Q

parts of the linac

A
  • gantry + stand = where radiation is produced
  • treatment couch
  • table 1
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15
Q

planning techniques for radiotherapy

A
  • 2d/conventional (xray): most simple
  • conventional ct = uniform intensity, square or rectangular
  • 3d conformal radiotherapy (3dcrt) = uniform intensity, irregular shapes
  • imrt = varying intensity, irregular shapes, higher conformity
  • igrt = changes per change in size, shape, and location of tumor
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16
Q

what is vmat

A
  • radiation can be shut out of machine while moving in 360 degree arc
  • quicker treatment delivery and improved dose homogeneity
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17
Q

advantages of stereotactic techniques

A
  • very high tumor dose
  • almost negligible dose to organs at risk
  • srs, sbrt or sabr
  • gamma knife, linac, tomotherapy, cyberknife
18
Q

machines that use stereotactic techniques

A

gamma knife!!, linac, tomotherapy, cyberknife

19
Q

3 most common extracranial cancer primaries or locations

A

lung, liver, bone

20
Q

common uses of brachytherapy

A

body cavities (gyne, npca) or close to surface (prostate, sarcoma, tongue, lip, breast)

21
Q

two actions in radiation therapy

A

direct action: radiation itself breaks the dna bonds

indirect action: radiation interacts with water to form hydroxyl groups, oxygen is important to make the damage more permanent

22
Q

radiation used in photon radiation

A

indirect action

23
Q

t/f cancer cells are better able to repair direct actions

A

false, indirect actions, due to more single stranded breaks of the dna compared to double strand breaks

24
Q

what is fractionation

A
  • irradiating small doses over many treatments
  • takes advantage of minimally improved survival of normal tissue at smaller doses
  • amplified over many treatments
25
Q

4 rs of fractionated radiation

A
  • repair
  • reassortment or redistribution
  • reoxygenation
  • repopulation
26
Q

principle of reassortment or redistribution

A

radiation causes cells to accumulate in certain phases of the cycle (g2 and m phase)

27
Q

principle of reoxygenation

A

tumors reoxygenate after radiation but when tumors reach a certain size, those cells farther away from the vessels are poorly oxygenated because diffusion of oxygen is limited

28
Q

principle of repopulation

A

normal cells are better at repopulation after radiation

29
Q

type of radiosurgery that has very high radiation doses resulting in ablation

A

stereotactic / srs / sbrt / sabr

30
Q

what are radiation protectors

A

agents that allow normal tissues to tolerate radiation more

31
Q

what are radiation sensitizers

A

agents that make the cancer more sensitive to radiation

32
Q

most common radiation sensitizers

A

chemo: 5fu, platinum analogs (cisplatin), gemcitabine, taxanes

targeted agents: egfr inhibitors!!, farnesyltransferase inhibitors, cox2 inhibitors, histone deacetylate inhibitors, hsp90 inhibitor

33
Q

ability of localized radiation to trigger systemic antitumor effects

A

abscopal effect

- molecules released after radiation improve defenses against cancer

34
Q

timing of toxicity

A

acute less/= 90 days of radiation

late >90 days

35
Q

radiotherapy can be curative for __

A

prostate cancer (and other urologic ca), breast ca, h&n ca, gyne ca (cervix), pediatric, cns, skin

36
Q

what is definitive rt

A
  • radiotherapy is the main treatment with or without systemic agent
  • objective is cure
37
Q

what is concurrent rt

A
  • rad given with systemic agent (chemo, targeted agent, immuno)
38
Q

what is neoadjuvant rt

A
  • rad given prior to surg with/without systemic agent

- goal is to improve surgical results

39
Q

what is adjuvant rt

A
  • rad given after surgery +/- systemic agent

- goal is to lower chance of recurrence

40
Q

methods to simulate and plan treatment

A
  • ct scan
  • fusion of images (software)
  • contouring
41
Q

volumes in contouring

A
  • gross tumor volume: seen or palpable tumor
  • clinical target volume: areas where there can be microscopic ca extension
  • planning target volume: isotopic margin or expansion to compensate for the possible setup uncertainty
  • internal target volume: not always done, but for when tumor moves (lung or liver)
42
Q

principle of proton therapy

A
  • there is sudden increase in deposition then no more after

- ideal to have less dose to organs at risk after the dose is given

14 Onco (27 decks)

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