Radio and Chemo Flashcards
(28 cards)
how does chemo work
prevents cancer cells from growing spreading by destroying the cells or stopping them from dividing
rest period allows normal cells and tissues to recover
healthy cells can repair the damage that chemo causes but cancers cells can repair themselves that well
(usually 3 weekly cycles - time needed for bone marrow to recover- 6 cycles make up a course of chemo)
what cells are likely affected by bystander effect of chemo
hair follicles, mouth, nails, gut mucosa, bone marrow
what is chemoradiation
chemo given with radio to enhance affects of radiation
what are the common SEs of chemo
mouth ulcers N+V fever diarrhoea alopecia bone marrow suppression (universal for all types) fatigue infertility photosensitivity
what do alkalyting agents do
e.g. cyclophosphamide
directly damages DNA and prevents cell division
works in all cell cycle stages
what do platinum alkylators do
e.g. carboplatin, cisplatin
direct damage to DNA and prevents cell division
what do antimetabolites do
e.g. methotrexate, 5 FU
interfere with building blocks of DNA synthesis
greatest activity in S phase
what do anti tumour antibiotics do
e.g. anthracyclines (doxuribuicin -the red one)
interfere with enzymes involved with DNA replication
all phases of cell cycle
what do topoisomerase inhibitors do
e.g. etoposide
interfere with topoisomerases (enzymes which help separate DNA strands prior to copying)
what do mitotic inhibitors do
e.g. taxanes, vinca alkaloids
prevent mitosis
M phase specific
what are 4 mechanisms for drug resistance
cancer cells may pump the drug out of the cell (p-glycoprotein pump)
cancer cells learn how to repair DNA damage caused by chemo
cancer cells develop a mechanism that inactivates the drug
gene amplification- overproduction of a protein that makes the chemotherapy ineffective
what is the best way of preventing drug resistance
using the best combo of drugs first when there is the least possibility of chemotherapy resistance
can surgery and radio be used to treat mets
no neither alone or in combo (unless radioactive iodine for thyroid)
what are the phases in the response of cells and tissue to radiation
physical- deposition of energy: ionisation and production of fast electrons. direction action= electron damage DNA
chemical: electrons interact with molecules to produce chemical changes- free radicals (e.g. hydroxyl OH) which damage biological targets= indirect effect
biological= the chemical damage has biological effects (can last a lifetime, usually through its effect on DNA)
how does oxygen affect radiation
the more oxygen present the more sensitive the cell is to radiation
in hypoxic conditions organic radicals can be repaired
in well oxygenated tissues organic peroxide (RO2) formed which makes repair impossible
radiation damage made permanent in the presence of oxygen
in tumour have hypoxic but viable cells
what is the different between physical dose and biological effect in chemo
dose= energy deposited in the medium
biological effect is not equal to the dose and depends on type of radiation, no. of particles, intervals between fractions, overall exposure time, dose rate, biological tissue
what is selective toxicity
devising treatment regime that causes minimal damage to the normal tissues but maximal harm to the tumour
based on relationship between dose and response (tumour, normal tissue)
what are the acute and late effect of radio timelines
acute up to 6 months after completion of treatment (usually effects on proliferating populations)
late affects after 6 months (usually parenchymal stem cells and vasculature)
what are the 5 rs that determine outcome of radiotherapy
repair- cells ability to repair radiation induced damage. want to inhibit healing in cancer cells and promote healing in normal cells
repopulation-want to not give tumour time to regrow between treatments- given every 3 weeks for e.g.
re-oxygenation- if radiation kills well oxygenated tumour cells then, after each fraction of treatment, there will be fewer tumour cells competing for the finite amount of oxygen that is present. Cells that were previously hypoxic may re-oxygenate and become sensitive to a subsequent treatment with radiation
Redistribution: cells vary in sensitivity to radiation according to cell cycle phase. In theory, schedules could be designed to exploit this. In practice, this is rarely achieved
Radiosensitivity: this may simply be an intrinsic, genetically driven, property of specific cell lineages. Some cell types may be less able to repair radiation-induced damage and therefore be intrinsically radiosensitive.
what repairs missing bases
base excision repair
what repairs SSB
base excision repair
what repairs bulk adducts
nucleotide excision repair
what repairs replication errors- wrong base
missmatch repair
what repairs DSB
homologous recombination/ NHEJ / alt NHEJ
