Rad Bio 6

Doubling time

the time required for a tumor to double in size

tumor load

refers to the number of cancer cells, the size of a tumor, or the amount of cancer in the body.

cell kill hypothesis

inverse relationship of cancer cells and curability

in order to cure cancer, every cancer cell must be killed. repeated courses of chemo must be given in order to reduce the total number

alkylating agents

forms molecular bond with nucleic acids, interfering with action

prevents mitosis

antimetabolites

interfere with synthesis of nucleic acids

antitumor antibiotics

disrupts DNA and RNA transcription

hormones

chemicals secreted by endocrine glands, alter the cells environment, by changing the cell membrane’s permeability

tumor growth can be affected by manipulating hormone levels

most commonly used for breast cancer - estrogen receptor +

nitrosoureas

Lipid soluble - can cross BBB (blood brain barrier)

DNA synthesis inhibited

vinca plant alkaloids

Cause mitotic arrest in metaphase

radioprotectors

~ protect normal tissues from radiation injury

~ scavenge free radicals before they damage DNA

~ enhance DNA repair in normal cells

~ ex: Amifostine

radiosensitizers

~ make tumor cells more sensitive to radiation

~ inhibit DNA repair mechanisms in cancer cells

~ mimic oxygen effect in hypoxic tumors

~ are usually common chemo agents

hyperthermia

medical manipulation of body temperature for treatment of disease

41.5 C - 46.5

temperature range for hyperthermia

thermal enhancement ratio

doses of x-rays required to produce a given level of biologic damage with and without the application of heat

external heating

~ superficial tumors

~ microwaves (433-2450 MHz)

~ radiofrequency (RF)

~ ultrasound

~ used for tumors within a few centimeters of the skin

interstitial heating

~ implanted probes/antennae placed directly into the tumor

~ delivers localized RF or microwave energy

~ effective for head and neck, prostate, or brain tumors

~ deep-seated tumors

intracavitary/intraluminal heating

~ heating devices placed into body cavities (rectum, bladder, esophagus, cervix)

~ useful for pelvic and GI cancers

Whole body hyperthermia

~ entire body heated using heated blankets, chambers, or perfusion

~ investigational; used for metastatic disease

regional perfusion hyperthermia

~ circulating heated blood or chemotherapy through a limb or organ

~ often combined with high-dose chemo

initiation

~ initiated cell appears somewhat normal

~ perhaps referred to as dysplastic or premalignant

~ still functions normally

promotion

~ altered cells proliferate

~ agent that encourages or enhances cell growth

progression

~ invasion

~ cells divide increase bulk

~ local spread

~ metastasis

proto-oncogenes

normal genes, control normal growth and differentiation

oncogene

genes that contribute abnormal proliferation of cells through point mutations, translocations, gene amplification

antioncogenes

~ also called tumor suppressor genes

~ inactivation allows the malignant process to thrive

latent period

time interval between irradiation and the appearance of a malignancy

~ leukemia has the shortest from atomic bomb survivor data (7-12 years)

lethal

~ before or immediately after implantation of embryo in uterine wall (before week 4)

OR

~ increased higher dose during all stages of development

malformations

exposure during major organogenesis in which main body structures are formed (week 5)

preimplantation

~ day 0-9 or roughly 2 weeks

~ most sensitive stage - causes radiation to be lethal

~ seems to be all or nothing - embryo either doesn’t implant and dies or implants and grows/develops normally

organogenesis

~ week 2-8

~ sensitive to a variety of congenital abnormalities

~ ex: organs developing outside of the body, growth retardation, facial abnormalities

~ if death is to occur, its typically neonatal

fetal

~ week 9-birth

~ more damage at earlier part of fetal phase

~ documented effects on hematopoietic system, liver, and kidney

~ gonads both morphologically (structure) and function in both genders

~ growth retardation (which can and can not repair)

1 Gy

Before 18 weeks, a dose of _____ will kill 50% if embryos

5 Gy

Before 18 weeks, a dose of ____ will kill 100% if embryos

microcephaly

most associated abnormalities with radiation in fetal stage

40%

an obstetric x-ray exam results in a ____ increase risk of childhood cancer over spontaneous level

5 mSv or 0.5 rem

exposure of fetus for entire gestation period

0.5 mSv or 0.005 rem

montly exposure for women to not exceed