Carcinogenesis, Hereditary & Embryonic Effects, & Radiation Protection Flashcards
Children who receive cranial radiation are most at risk for developing ….?
Meningiomas
Which organ can develop both malignant and benign growths following radiation?
Thyroid
What % of TBI patients develop life-threatening leukemias?
15%
What kind of cancers have and have not been detected in children treated w/ RT for tinea capitis?
Have:
- Brain
- Thyroid
- Adenomas
- Leukemias (non-CLL)
- Breast
Have NOT
- H&N
What kind of cancers did radium dial painters develop, and why?
Osteosarcomas: They licked their paint brushes and ingested radium, which localized to their bones.
Does radiation cause death from causes other than second cancers?
Yes, from toxicity to the circulatory, digestive, and respiratory systems.
What kind of a trend b/w dose and cancer risk do solid tumors fit?
- Linear
- Non-threshold (stochastic)
What kind of a trend b/w dose and cancer do leukemias fit?
- Linear-quadratic
- Non-threshold (Stochastic)
Does radiation risk depend on gender?
Yes!
Does radiation risk depend on age?
- Yes, very young children are most at risk
– Children < 5 yrs are 3x more susceptible than the average population, or 10x more susceptible than older adults - Very old individuals are also more radiosensitive
What is a stochastic effect?
An effect whose probability but NOT severity increases with dose. It usually does not have a threshold dose and is an all-or-none effect.
What is a deterministic effect?
- Has a threshold dose
- Severity related to dose
- Continuous effect, as opposed to all or none
What was the cause of thyroid cancers in children affected by the Chernobyl disaster?
Ingestion of I-131
When did thyroid cancers occur in children affected by the Chernobyl disaster?
7-10 yrs post-disaster
What is radiogenic cancer?
Cancer linked to radiation
Which source contributes the most to radiation exposure in the US?
Medical ≥ 50%
Which source is the second most common source of radiation exposure to people in the US?
Background ≥ 37%
Which medical procedure(s) contribute the most to medical radiation exposure?
- CT Scanners
- NM procedures
Individuals treated for enlarged thymus as children are at an increased risk of which cancer?
Thyroid
What is the tissue weighting factor for the breast, lungs, bone marrow, stomach, colon, and other tissues not mentioned elsewhere?
0.12
What is the tissue weighting factor for the gonads?
0.08
MNEMONIC: 2 round testes, 2 ovaries → 8
What is the tissue weighting factor for the thyroid, esophagus, bladder, and liver?
- 0.04
- The BELT organs: Bladder, Esophagus, Liver, Thyroid
What’s the sum of all tissue weighting factors?
1 (100%)
What is the tissue weighting factor for the brain, skin, bone surface, and salivary glands?
0.01
What is the increased % risk for the development of fatal cancers in radiation oncologists?
1%
Did the use of X-rays during the 50s and 60s increase the risk of childhood cancer in children who received these exams in utero?
Yes!
What is the radiation-induced malignancy rate for low DDREF radiation for all and working populations?
All - 5%
Working - 4%
What is the radiation-induced malignancy rate for high DDREF radiation for all and working populations?
All - 10 %
Working - 8%
What is a low dose and dose rate effectiveness factor (DDREF)?
Low LET radiation AND
Dose < 0.2 Gy OR Dose Rate < 0.1 Gy/hr
What is a high dose and dose rate effectiveness factor (DDREF)?
Low LET radiation AND
Dose > 0.2 Gy OR Dose Rate > 0.1 Gy/hr
OR
High LET radiation at any dose or dose rate
What is an equivalent dose (Sv)?
It is dose weighed for radiation type
What is an effective dose (Sv)?
The sum of weighted equivalent doses for all tissues and organs of the body is called the “effective dose”
What is the latent period for radiation-induced leukemias?
3-7 yrs
What is the minimum latent period for radiation-induced solid tumors?
≥ 10 yreas
Treatment for which benign spine disease is linked to an increased incidence of leukemia?
Ankylosing Spondylitis - 2/2 bone marrow expxosure
How many lung cancer deaths per year are attributable to exposure to indoor radon?
10-20%
20k out of 160k
What % of second malignancies in breast cancer patients are attributable to radiation?
5%
What kind of second malignancies are irradiated breast cancer patients most at risk for?
Esophagus
Lung
Soft tissues
What is the absolute risk model for radiation carcinogenesis?
Predicts the appearance of a distinct crop of radiation-induced cancers after a latent period following irradiation.
What is the relative risk model for radiation carcinogenesis?
Radiation-induced cancer risk is the natural incidence multiplied by a factor.
Has the incidence of cancer in the Japanese atomic bomb survivors plateaued?
No, it continues to increase to this day.
The incidence of which cancer was increased in women receiving fluoroscopies for pulmonary TB treatment?
Breast
What % of cancers in the Japanese atomic bomb survivors are leukemias?
20%
What is the probability of hereditary disorder in the first generation born to parents exposed to radiation for whole and working population?
- Working population: 0.1%/Gy
- Whole population: 0.2%/Gy
What is the annual dose of radiation attributed to medical diagnostic tests?
3 mSv (50%)
How does background radiation vary with altitude?
Increase, since there is a decrease in atmospheric shielding of cosmic rays
What is the annual dose of radiation attributed to a combined exposure to cosmic, terrestrial, and internal background radiation?
3 mSv
Under what condition are the equivalent and effective radiation doses equal?
When the whoel body is irradiated
What is the largest contibuter to background radiation in the US?
Radon
How much of the annual medical radiation exposure is received by the gonads?
0.3 mSv (10%)
How much of the annual medical radiation exposure is received by the gonads?
0.3 mSv (10%)
What sources of radiation are exempted from the annual radiation dose limit?
Background radiation, and radiation from medically necessary procedures.
Is metal retardation deterministic or stochastic?
Both.
It is deterministic when the fetus received radiation in utero.
It is stochastic when the egg/sperm received radiation prior to conception.
What’s doubling dose?
- Dose required to produce as many mutations as would occur spontaneously (spontaneous = radiation-induced)
- The total amount of mutations would thus be doubled (spontaneous + radiation-induced)
In the megamouse study, what was the doubling dose?
1 Gy
What’re the main conclusions of the mega mouse project?
- Radiosensitivity of different mutations varies 2/2 differences in gene sizes
- Dose rate effect: Acute doses of radiation result in more mutations than low-dose-rate exposures 2/2 DNA repair
- Heritable consequences of radiation can be greatly reduced by allowing time between irradiation and conception 2/2 repair
- The estimated doubling dose is 1 Gy w/ low-dose-rate exposure
in the mega mouse study, which sex was more susceptible to radiation-induced mutagenesis?
Males > Females
In the mega mouse study, what was the effect of low dose rate on mutagenesis?
Low dose rate decreased mutagenesis 2/2 ability to repair DNA at low doses
A study of Japanese A-bomb survivors by the Radiation Effects Research Foundation showed what effect of radiation on mutations in the F1 generation?
No effect, contrary to animal studies
What was the average dose received by the Japanese A-bomb survivors?
≤ 100 mSv
Do we have accurate dosimetry for the radiation exposure of the Japanese A-bomb survivors?
Yes!
Are the Japanese A-bomb survivors compliant with continued follow-up and testing?!
VERY
Does radiation induce new mutations in the population?
No, it only increases the frequency of mutations already seen within the population.