SM_283b: Radiation Oncology Flashcards
Goal of radiation of therapy is to ___
Goal of radiation of therapy is to prevent disease spread or stop the disease
Describe treatment paradigms for radiation
Treatment paradigms for radiation
- Curative: primary (radiotherapy alone), ± chemo (concurrent, sequential), ± surgery (preoperative, postoperative)
- Palliative
Describe when radiation is primary treatment
Radiation is primary treatment
- Small cell lung cancer
- Locally advanced cervical cancer
- Anal cancer
- Laryngeal cancer
- Medically inoperable early stage NSCLC
- Locally advanced head and neck cancer
- Localized lymphoma
Radiation is used preoperatively to ___
Radiation is used preoperatively to improve the chance or margin of resection and reduce risk of locoregional recurrrence
- T3 or N+ rectal cancer
- Stage IIIA lung cancer
- Sarcoma
- Borderline resectable pancreatic cancer
Radiation is used postoperatively with the goal of ___
Radiation is used postoperatively with the goal of eradicating subclinical disease
- Breast conservation
- Breast cancer after mastectomy (node +)
- Endometrial cancer
Radiation is used as salvage therapy if there is ___
Radiation is used as salvage therapy if there is evidence of recurrence after surgery
- Post-prostatectomy recurrence
- Vaginal recurrence after hysterectomy for endometrial cancer
Radiation is used as palliative therapy when there is ___, ___, ___, and ___
Radiation is used as palliative therapy when there is pain, bleeding, compression, and SVC syndrome
Describe goals of radiotherapy for cancer
Goals of radiotherapy for cancer
- Deliver precise measured dose to targeted volume
- Eradicate tumor and microscopic disease
- Cure / prolong survival
- Minimize damage to adjacent normal tissue
- Minimize side effects
- Provide pts with high QOL
- Provide effective palliatipn
Describe steps of radiotherapy
Radiotherapy steps
- Consultation
- Treatment planning
- Simulation: positioning, immobilization device
- 3D reconstruction
- Target definition
- Planning / optimization
Stereotactic treatment is used to treat ___
Stereotactic treatment is used to treat cranial and extracranial treatment
- Stereotactic radiosurgery: intracranial
- Stereotactic ablative body radiation: lung, liver, spine lesions
- Small well-defined targets
- Advanced image guidance
- High dose per fraction
- Use of multiple beams
Describe GammaKnife stereotactic radiosurgery
GammaKnife stereotactic radiosurgery
- Stereotactic frame and immobilization
- Intracranial treatment (single fraction)
- MRI done same day
- 192 beamlets converge on single point / isocenter
X-rays are produced ___ in ___
X-rays are produced extranuclearly in powerful electrical devices that accelerate e- to high energy
Gamma rays are produced ___ in ___
Gamma rays are produced intranuclearly when emitted by radioactive isotopes
Brachytherapy is ___
Brachytherapy is type of radiotherapy that involves placing radiation inside the body
___ is used to shape beams
3D conformal treatment via computerized MLCs is used to shape beams
Intensely modulated radiotherapy uses ___
Intensely modulated radiotherapy uses linear accelerators to safely deliver radiation to a tumor while minimizing dose to surrounding normal tissue
Rough rule for radiobiology is ___
Rough rule for radiobiology is per cell / per Gy ~ 1000 SBB: high fidelity repair, 40-50 DSB produced which is most biologically significant, > 1000 damaged bases
Principal driver of radiotherapy biologic effects is ___
Principal driver of radiotherapy biologic effects is DNA double stranded breaks
- 1/3 direct damage: direct radiotherapy induced ionization of DNA
- 2/3 indirect damage: ionization lading to free radical chain reaction
Describe role of oxygen in radiobiology
Role of oxygen in radiobiology
- Radiolysis of water
- Oxygen: binds H radicals forming hydrogen peroxide, binds electrons to create superoxide, binds organic radicals to form peroxides
Radiosensitivity varies with ___
Radiosensitivity varies with cell cycle
- Maximum sensitivity to M phase and during G2
- Decreased sensitivity during S phase
- Variable during G1 phase: decreased sensitivity with longer G1 phases
Four R’s of fractionation in radiobiology are ___, ___, ___, and ___
Four R’s of fractionation in radiobiology are re-oxygenation, redistribution, repair, and repopulation
Fraction of radiation ___ important than total dose
Fraction of radiation more important than total dose
Biologically equivalent dose is ___
Biologically equivalent dose is determined by a linear quadratic theory
Discuss grading of radiotherapy toxicity
Grading of radiotherapy toxicity
- No intervention
- Intervention
- Significant intervention
- Life-threatening
- Death
Describe acute radiation toxicity
Acute radiation toxicity
- Epithelial surfaces, hematocytopenia, inflammatory cascade
- Skin toxicity
- Grade 1: erythema
- Grade 2: dry desquamation
- Grade 3: moist desquamation
Describe late radiation toxicity
Late radiation toxicity
- Vascular structures, fibrosis, parenchymal cell death
- Telangiectasia
- Fibrosis (retraction)
