RADIATION THERAPY QUESTIONS AND
ANSWERS
Accelerated Fractionation A reduction in overall time without a change in dose per
fraction or total dose
Delivers fractional doses of 150-200 cGy
Multiple treatments per day
Total dose remains the same
Overall treatment time is halved
Hypofractionation Use of large daily fractions, however, the patient is not treated 5 days
per week
Dose per fraction is increased
Total dose is decreased
Late side effects are greater
Split Course Treatment Larger fractions are used daily causing an increased reaction
which requires the course to be split with a few weeks rest between courses.
Irradiated Volume A major factor in determining a tolerance dose is whether whole organ
versus partial organ is exposed to radiation
Time The interval between fractions and overall duration of treatment affect tolerance
dose.
, Controlling Factors Three major factors that must be controlled and monitored when
administering radiation therapy
Treatment volume
Dose distribution
Dose fractionation
Chemotherapy Adding chemotherapy and the timing of its delivery relative to treatment
has a major impact on sensitivity
Innovations Hyperthermia
Radiosensitizers
Radioprotectors
Immunological and biological response modifiers
Tolerance Organ tolerance is determined by the radiosensitivity of the relevant stem cell
subpopulations, which may not always be proliferating or dividing
The tolerance of the normal tissue is the limiting factor in the dose given
Tumor Lethal Dose A dose of radiation that creates complete and permanent regression
(removal - killing) of the tumor.
Is defined as the dose which achieves 95% tumor control
Nominal Standard Dose Used to compare and contrast treatment regimens and the
biologic effects that differ in dose, fractionation and overall treatment time
Tumor Control Tumor control is directly related to the radiation dose and inversely
proportional to the number of tumor cells
ANSWERS
Accelerated Fractionation A reduction in overall time without a change in dose per
fraction or total dose
Delivers fractional doses of 150-200 cGy
Multiple treatments per day
Total dose remains the same
Overall treatment time is halved
Hypofractionation Use of large daily fractions, however, the patient is not treated 5 days
per week
Dose per fraction is increased
Total dose is decreased
Late side effects are greater
Split Course Treatment Larger fractions are used daily causing an increased reaction
which requires the course to be split with a few weeks rest between courses.
Irradiated Volume A major factor in determining a tolerance dose is whether whole organ
versus partial organ is exposed to radiation
Time The interval between fractions and overall duration of treatment affect tolerance
dose.
, Controlling Factors Three major factors that must be controlled and monitored when
administering radiation therapy
Treatment volume
Dose distribution
Dose fractionation
Chemotherapy Adding chemotherapy and the timing of its delivery relative to treatment
has a major impact on sensitivity
Innovations Hyperthermia
Radiosensitizers
Radioprotectors
Immunological and biological response modifiers
Tolerance Organ tolerance is determined by the radiosensitivity of the relevant stem cell
subpopulations, which may not always be proliferating or dividing
The tolerance of the normal tissue is the limiting factor in the dose given
Tumor Lethal Dose A dose of radiation that creates complete and permanent regression
(removal - killing) of the tumor.
Is defined as the dose which achieves 95% tumor control
Nominal Standard Dose Used to compare and contrast treatment regimens and the
biologic effects that differ in dose, fractionation and overall treatment time
Tumor Control Tumor control is directly related to the radiation dose and inversely
proportional to the number of tumor cells
