Lec 22 - Radiation and Oncology Flashcards
4 basic patterns of spread
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
3 main treatments
1) surgery
2) medical therapy -chemo, hormone, biologic, vaccine
3) radiation therapy
adjuvant meaning
usually done after main treatment (aka surgery in most)
neoadjuvant meaning:
before the mos important treatment
RT used as adjunct cancer examples:
Breast cancer
skin cancer
prostate cancer
uterineendometrium
RT used as neoadjuvant cancer examples:
esophgeal
rectal CA
pancreaticCA
extremity sarcoma
a radiosensitive tumor does what with radiation?
melts!
radioresponsive tumor does what with RT?
melts quickly!
4 Rs of radiation therapy
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
How RT works…
- 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
radiosensitive phase of cell cycle=
M/G2
radioresistant phase of cell cycle =
S
therapeutic ratio
TCP is greater than NTCP = thats why radiation is useful
what type of cells are more radioresistant?
hypoxic cells - O2 for some reason seems to enhance ability to cause double strand DNA breaks
reoxygenation allows for?
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
standard fractionation dosing
180-200cGy 1x/day
palliative standard dosing?
300 cGy daily
hyperfractionation dose and good for?
120-150cGy 2x/day
good for rapidly dividing cancers
hypofractionation dosing
800-2200cGy for 1-3 fractions
give a tumor one really good whack
curative intent treatement style
larger # treatments and lower dose per treatment
palliative intent treatment:
smaller # treatments and higher dose per treatment
5 levels of treatment complexity
nonplanned 2D plan 3DCRT plan IMRT Plan SRS/SBRT plan
2D plan
do a scan and dont measure but just do it? make up the dose bro
3DCRT plan
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
