Rad Onc Flashcards
Four “R”’s of radiation oncology
- Improved normal tissue tolerance
- Repair
- Repopulation
- Enhanced disease tissue killing
- Redistribution
- Reoxygenation
At what point in the cell cycle are cells most sensitive to radiation?
- G2 (especially end of G2)
- Two reasons:
- Greastest quantity of DNA
- Multiple checkpoints
2/3 of the effectiveness of radiation therapy comes from ___
2/3 of the effectiveness of radiation therapy comes from indirect effects
In other words, hydroxyl free radicals
This is why reoxygenation is so important for radiation therapy
High dose radiation to a tubular structure
“Pop”
Proton vs photon beam radiation
Radiation therapy for medulloblastoma
Full craniospinal proton beam radiation
We have to treat the whole spine due to risk of drop metastasis. This can be curative.
Proton beam is to reduce side effects to organs.
The various types of radiation therapy
Electrons deposit radiation at ___
Protons deposit radiation at ___
Electrons deposit radiation at the very surface
Protons deposit radiation at depth
Radium seeds
Emit photon radiation highly locally with no entrance or exit dose
Excellent way to treat local prostate cancer
General acute and late radiation side effects
Cerebral acute and late radiation side effects
Sparing hippocampi helps reduce neurocognitive side effects
Oropharynx acute and late radiation side effects
Radiation pneumonitis looks a lot like. . .
. . . pneumonia OR tumor progression
You have to be able to differentiate them with clinical features and timing, because the treatments are different! Antibiotics vs more radiation vs steroids
Timeframe for radiation-associated inflammation
Radiation pneumonitis: 6-12 months post-treatment
Leukoencephalopathy: Progressive over time
Diarrhea/Colitis/Proctitis: Acute, when on treatment. But, telangiectasias may be formed that can bleed at any time in the future.
Mitomicin C
Used for anal cancers – sensitizes to radiotherapy by increasing oxygen delivery in the tumor
