Lec 22 - Radiation and Oncology

Question 1

4 basic patterns of spread

Answer 1

1) local growth-tumor itsle fenlarges over time (size or depth)
2) local extension - tumor invades adjacent organs
3) lymph node metastases
4) hematogenous metasteses - ex prostate to bone and small cell lung to brain

Question 2

3 main treatments

Answer 2

1) surgery
2) medical therapy -chemo, hormone, biologic, vaccine
3) radiation therapy

Question 3

adjuvant meaning

Answer 3

usually done after main treatment (aka surgery in most)

Question 4

neoadjuvant meaning:

Answer 4

before the mos important treatment

Question 5

RT used as adjunct cancer examples:

Answer 5

Breast cancer
skin cancer
prostate cancer
uterineendometrium

Question 6

RT used as neoadjuvant cancer examples:

Answer 6

esophgeal
rectal CA
pancreaticCA
extremity sarcoma

Question 7

a radiosensitive tumor does what with radiation?

Answer 7

melts!

Question 8

radioresponsive tumor does what with RT?

Answer 8

melts quickly!

Question 9

4 Rs of radiation therapy

Answer 9

1) repair- splitting radiation into small parts, normal tissue cells are allowed to repair sublethal damage but tumor cells cant do this as well
2) redistribution: allow tumor cells to move into the most sensitive phases of cell cycle over time
3) reoxygenation- allow “inner” hypoxic tumor cells to get a greater exposure to oxygen over the course of treatment
4) repopulation: delivering continuous, daily blows to tumor cells prevents them from repopulating and thriving

Question 10

How RT works…

Answer 10

• DNA of well-oxygenated tumor cells appears to be the main target for biological effect of radiation
• most important lesion induced is adouble strand DNA break

Question 11

radiosensitive phase of cell cycle=

Answer 11

M/G2

Question 12

radioresistant phase of cell cycle =

Answer 12

S

Question 13

therapeutic ratio

Answer 13

TCP is greater than NTCP = thats why radiation is useful

Question 14

what type of cells are more radioresistant?

Answer 14

hypoxic cells - O2 for some reason seems to enhance ability to cause double strand DNA breaks

Question 15

reoxygenation allows for?

Answer 15

progressvie killing of tumor cells

kill the outer oxygenated cell–> reoxygenate outer cells of what didnt die –> kill that new outer oxygenated area… on and on

Question 16

standard fractionation dosing

Answer 16

180-200cGy 1x/day

Question 17

palliative standard dosing?

Answer 17

300 cGy daily

Question 18

hyperfractionation dose and good for?

Answer 18

120-150cGy 2x/day

good for rapidly dividing cancers

Question 19

hypofractionation dosing

Answer 19

800-2200cGy for 1-3 fractions

give a tumor one really good whack

Question 20

curative intent treatement style

Answer 20

larger # treatments and lower dose per treatment

Question 21

palliative intent treatment:

Answer 21

smaller # treatments and higher dose per treatment

Question 22

5 levels of treatment complexity

Answer 22

nonplanned
2D plan
3DCRT plan
IMRT Plan
SRS/SBRT plan

Question 23

2D plan

Answer 23

do a scan and dont measure but just do it? make up the dose bro

Question 24

3DCRT plan

Answer 24

uses computer based treatment planning

• treat and avoid normal structures as much as possible
• downfall is that it leaks into other tissues
• not such a good option anymore - cant conform to specific organ shapes

Question 25

Dose volume histogram shows?

Answer 25

with 3DCRT shows how much of the target and normal structures are receiving certain doses

Question 26

IMRT plan

Answer 26

like 3DCRT but it conforms to whatever shape your target is

Question 27

SRS/SBRT plan

Answer 27

pretty mcuh as good as you can get to not damage other tissues

Question 28

photons

Answer 28

due to gradual fall off treats deep lesions - build up strength
skin sparing
can combine fields for better dose distribution

Question 29

electrons

Answer 29

reats shallow lesions
definite range
usually single field

Question 30

stereoscopic IGRT is for

wat is it?

Answer 30

bony lesions or non soft tissue

basically youre constantly readjusting for movement

Question 31

cone beam IGRT is for?

what is ti?

Answer 31

for soft tissue

bassically youre constantly readjusting for movemnt