EXAM #2: RADIATION ONCOLOGY Flashcards
What is the most fatal cancer in the world?
Lung
What are the three most common cancers in men?
Prostate
Lung and bronchus
Colon and rectum
What are the three most common cancers in women?
Breast
Lung and bronchus
Colon and rectum
What are the four basic patterns of cancer progression?
1) Local-growth
2) Local-extension i.e. tumor invades adjacent organs
3) Lymph node metastases
4) Hematogenous metastases
What stage does local tumor growth determine?
T-stage
What stage does local extension affect?
Upstaging the T-stage
What stage does lymph node metastases affect?
N-stage
What stage does hematogenous metastasis affect?
M-stage
What cancers does radiation take the place of surgery in?
1) Anal
2) Limited stage small cell lung
3) Esophageal
4) Stage IIIB non-small cell lung cancer
What cancers is radiation used as an adjuvant therapy in?
1) Breast
2) Skin with positive margins
3) Prostate
4) Uterine/ endometrial
Note that radiation is used AFTER the main surgical treatment
What is radiation?
Use of EM and particulate ionizing raidation
How is the dose of radiation measured?
Gray
What is the most common form of radiation?
Daily external delivery of photons i.e. x-rays over multiple weeks
Why is external beam radiation therapy given over time?
This is required for maximal tumor kill and minimal damage to normal tissue damage
What does radiosensitive mean?
Tumor melts with radiation
What does radioresponsive mean?
Tumor melts quickly with radiation
What is Brachytherapy?
Any source that emits a halo of radiation
E.g. prostate seeds
What is the most important lesion induced by radiation?
Double strand DNA break
What is the most radiosensitive phase of the cell cycle?
M/G2
What is the radioresistant phase of the cell cycle?
S
What is the RT in radiation therapy? What are the implications?
Theraputic ratio of radiation, like a TI
The bigger the number the more cancerous tissue is specifically targeted
Why are hypoxic cells the most radioresistant?
Oxygenation enhances ds-DNA breaks
What part of tumors is the most hypoxic?
Central portion
What is the standard dose of radation?
180-200 cGy per day
What is hypofractionation dose radiation?
Very high dose radiation
What types of cancer are typically radiated for palliative reasons?
Brain mets
Bone mets
What are the five levels of treatment complexity in radiation?
1) Non-planned
2) 2D
3) 3DCRT
4) IMRT
5) SRS/FSRT/SBRT
What is 3D-CRT?
- Computer based treatment plan
- Designs treatment to target the tumor and avoid normal structure
Causes a “leaking” or radiation into nearby critical structures
What is IMRT?
Intensity-modulated radiation therapy (IMRT) is a high-precision radiotherapy that uses computer-controlled linear accelerator to deliver precise radiation doses to a malignant tumor
This prevents harm to surrounding structures and is at limiting collateral damage than 3D-CRT*
What is SRS?
Stereotactic Radiosurgery
This creates an x,y, and z axes to localize brain lesions*
What is the cyber knife?
Robot used today for brain tumor localization
What is the definition of GTV?
Gross Tumor Volume i.e. the volume of tumor that can be imaged
What is the definition of CTV?
Clinical Target Volume, the gross tumor volume plus the margins of assumed sub-clinical disease
What is the definition of ITV?
Internal Target Volume,this is a volume that accounts for the movement of the CTV in a patient
What is the definition of PTV?
Panning target volume, a volume intended to compensate for errors in planning and set up
What does OAR stand for?
Organs at Risk
Why is a CT done for every patient?
Planning
What is “fusion?”
Fusion of the planning CT and other imaging modalities
What are photons best for treating?
Deep lesions
What are electrons best for treating?
Superficical lesions
What type of beam block is the current standard of care?
Multileaf Collimator (MLC)
What is a portal film?
Image used to verify the correct setup for radiation based on bony landmarks
What is IGRT?
Image Guided Radiation Therapy
This is a special imaging technology that allows the physician to image the tumor immediately before or during the time radiation is delivered. These images are then compared to the reference images taken during simulation. Any necessary adjustments are then made to the patient’s position and/or radiation beams in order to more precisely target radiation at the tumor and avoid healthy surrounding tissue.
What is stereoscopic IGRT?
This is an imaging technique, IGRT, that uses bones as landmarks
It is difficult to use for deep soft tissue targets are there are no bony landmarks in close proximity*
What is stereoscopic IGRT poor for?
Soft tissue targets
What is cone beam IGRT best for?
Soft tissue targets
