M6S3: Cancer And Chemotherapeutics Flashcards
Introduction to cancer
-refers to group of diseases that primarily affect Canadians 50 years or older
-45% of males and 43% of females will develop cancer at some point
-aka 1 in 2.3 people will get cancer
-around 30% of Canadians deaths due to cancer
-most common types include lung, breast, colorectal, prostate (lung = leading cause of death)
Key features of cancer cells
-cancer generic term for large number of diseases that involve abnormal groups of cells that share 3 features:
1. Cell growth and Division: ability to proliferate indefinitely
2. Invasion: ability to invade surrounding normal tissue
3. Metastasis: ability to spread throughout body
Causes of cancer
Genetics
-can contribute to variation in response to carcinogens
Ex. People who have condition known as xeroderma pigmentosum have genetically-based deficiency in DNA repair
-as result, these people are prone to mutations and therefore, have high incidence of skin cancer
Environmental factors
-include all non-genetic elements like environmental chemicals, diet and infections
-modifiable
Steps in carcinogenesis
*refer to goodnotes
Environmental factors and cancer risk
Tobacco use
-smoking causes cancers like lung, esophageal, bladder, pancreatic cancers
-in addition to genetic factors, whether smoking results in development of cancer will depend upon the tar content of cigarettes smoke, frequency, and duration
-smokers 8 times more likely to get lung cancer
- passive smoke (inhaled from enviro) also risk factor for cancer
-more 800 Canadians who do not smoke die from second hand smoke every year
Adult diet
-saturated animal fat and red meat link to cancer of colon, rectum and prostate
-high intake of salt linked to stomach and other cancers
-skimping on fresh fruits and vessels can contribute to different cancers as thought that fruits and veggies contain constituent that block cancer-inducing chemicals produced in body
Occupational factors
-strict control measures have cut down on cancer caused by these exposures but measures are not as well instituted in developing countries, making it likely that carcinogens in workplace are major hazard
Viruses and infections
-both bacterial and viral infections liked to cancer
Bacteria -> heliocobacter pylori, the bacterium responsible for causing stomach ulcers, strongly associated with stomach cancer
Viruses -> hepatitis B and hepatitis C can cause liver cancer. Estimated that 80% liver cancer caused by hepatitis. Human papillomavirus (HPV) (sexually transmitted) can cause cervical cancer
*refer to goodnotes
Cancer prevention (can only occur through environmental factors, not genetics)
Avoid excessive exposure to sunlight
-this decreases risk of skin cancers
-if exposured use sunscreen
Monitor alcohol intake
-associated with increase number of cancers like mouth and liver cancers
Eliminate use of tobacco products
-will greatly decrease risk of developing lung cancer and other cancers associated with tobacco use
Eat healthy
-maintain adequate diet of fruits and veggies
-moderate consumption of saturated fats and red meats
Be active
-maintaining healthy lifestyle will ensure body is in its best form to combat the carcinogens its exposed to on a daily basis
Get vaccinated
Hepatitis B can cause liver cancer, while HPV can cause cervical cancer
Vaccinations for both these viruses are available in Canada
Goals of cancer treatment
*defer based on severity of symptoms
Prevent the cancer
-treatment given to prevent cell growth or to remove precancerous cells that could turn into cancer (ex. Mole)
Cure the cancer
-primary goal of treatment but cure has been achieved for only a few cancers like testicular cancer, Hodgkin’s disease, and childhood leukaemia’s
Control the cancer
-when cure not possible, control cancer is goal to stop growing, spreading and prolong patient survival
Relieve symptoms
-make patient comfortable for example medication for controlling pain and nausea
Drugs used to treat cancer
Main types of treatment: surgery, chemotherapy (kills cancer cells), radiation, bone marrow transplant
Chemotherapeutic drugs
Act by: slowing the growth of rapidly dividing cells
-in general, drugs inhibit DNA synthesis, protein synthesis, or cell division through variety of ways
-newer agents act directly against abnormal protein in cancer cells and are therefore more a targeted therapy than traditional chemotherapeutic drugs
Several classes exist, ranging in specificity of their target
1. Alkylating agents -> bind to and interfere with DNA replication
2. Mitotic inhibitors -> affect microtubule function and formation of mitotic spindle, thereby preventing cell division
3. Hormones and hormone antagonists -> treat hormone sensitive tumours by suppressing cell division
4. Biologicals -> number of drugs derived through molecular biological techniques inhibit cell replication by blocking cytokines, which normally control cell growth. Some drugs also antibodies to these cytokines
Principles of cancer chemotherapy
-when designing cancer chemotherapy regimen, a couple of factors need to be considered
Benefit-risk assessment
-healthcare team, in consultation with the patient, must weight the possible benefits verse adverse effects of treatment in each clinical situation
Ex. Continuously dividing cells in body also harmed by most drugs employed in cancer chemotherapy so cells lining GI tract also harmed, resulting in nausea, vomiting, ulceration. Hair roots harmed too, resulting in hair loss
-additionally, each type chemotherapeutic associated with own toxicities
-decision whether or not to continue chemotherapy need to be re-evaluated prior to each treatment
Combination chemotherapy
-chemotherapy drugs typically combined as:
Development of resistance -> over time, cancer cells can become resistant to chemo. Cancer cells less likely to develop resistance when attacked by variety of drugs that act in different ways
Occurrence to toxicities -> chemo drugs have low therapeutic indexes. If single drug used, not possible to increase dose beyond a certain level because of toxicities. Combining drugs allow for selection of chemotherapeutic with different toxicities. Dose and schedule carefully evaluated
