Flashcards in 03/02c Neoplasia II Deck (46):
What is epidemiology?
The study of the distribution and determinant of health-related states or events in specified populations, the the application of this study to control of health problems
What is the definition of cancer INCIDENCE?
Incidence is how many people are diagnosed with cancer in a given time period (often 1 year)
What is the definition of cancer PREVALENCE? What factors determine prevalence?
Prevalence is how many people (total) have the cancer in a given time period
Depends on incidence, length of survival, and mortality rates
What percentage of the US population has had cancer?
What is the relationship between cancer and age?
Cancer is largely a disease of the older population; incidence increases with age
What are the top four most common cancers that cause death in the US?
Why have lung and bronchus cancer death rates increased so much between the 1930s and now?
What is the absolute difference in cancer survival rates between the white and black populations?
What happens to your chances of getting a certain type of cancer if you move to different country?
You acquire the cancer rates of the country that you move to
What are most cancers caused by? What does this mean?
The majority of cancer are thus preventable, if we can figure out what in the environment is causing them
What are three characteristics of inherited cancers that distinguish them from sporadic cancers?
Cancer develops in a large proportion of afflicted patients
Usually early onset
What percentage of all cancers are inherited cancers?
What are the three broad categories of inherited cancers?
Unclassified familial clusters
What are unclassified familial clusters?
Family that has a high rate of cancer, but with an unclear mechanism of inheritance and no genetic defect identified
What are four important features of autosomal dominant cancers?
Have very specific sites or tissues that are affected by cancer
Can have incomplete penetrance and variable expressivity
Can have multiple benign tumors in the target tissue, as well as malignant tumors
Can have characteristics non-neoplastic lesions in other tissues
What are two classic examples of non-neoplastic lesions characteristic in cases of neurofibromatosis?
Café au lait spots on the skin
Lisch nodules in the eye
How much more likely are you to develop retinoblastoma if you have the mutated Rb gene?
10,000x more likely
What are five important features of autosomal recessive cancers?
Rare in comparison to autosomal dominant cancers
Usually have complete penetrance
Tumors usually arise in sites exposed to mutagens (UV light, radiation, etc.)
Typically have complex, multi-system effects
Mostly due to defects in DNA repair
What three things can happen to a cell that has accumulated a large amount of DNA damage?
Enters senescence (irreversible dormancy)
Develops unregulated cell division, leading to the formation of a tumor
What is ataxia telangiectasis?
Autosomal recessive cancer
Characterized by progressive neurologic impairment, cerebellar ataxia, immundeficiency with susceptibility to infections, impaired organ maturation, and X-ray sensitivity
Mutation in a gene that senses DNA double-stranded breaks and initiates cell cycle arrest or cell death
What is xeroderma pigmentosum?
Autosomal recessive cancer in which nucleotide excision repair enzymes are mutated, and thus cells cannot repair damage to DNA caused by UV light
Patients present with severe sunburns after only a short sun exposure, and are susceptible to developing basal cell carcinoma and other skin malignancies at a young age
What is Lynch Syndrome?
Hereditary Nonpolyposis Colon Cancer (HNPCC) - most common inherited colon cancer
Causes cancers of the colon, endometrium, and ovary
Autosomal dominant inheritance pattern
Caused by a DNA repair defect
What three features of a cancer would lead you to believe it was an unclassified familial cancer?
1) Cancers seen in multiple close relatives
2) Multiple cancers seen in individuals
3) Persistence of cancers over several generations
What broad non-hereditary medical condition can predispose you to cancer?
May be due to infection, autoimmunity, or be medically induced
What are some cancers that are caused by inflammation associated with infection?
Helicobacter pylori gastritis - gastric cancers
Chronic osteomyelitis - squamous cell cancer in fistula tracts
Viral hepatitis - liver cancer
What are some cancers that are due to inflammation caused by autoimmune conditions?
Colon cancer - ulcerative colitis
Bile duct cancer - sclerosing cholangitis
What is a pre-cancerous lesion?
A lesion with a marked increase in cancer at the site
Obligate precursor - remove it and cancer is prevented, but not all will progress to cancer
What is a carcinogen?
An external agent that increases the incidence of malignant neoplasms, reduces their latency, or increase their severity or multiplicity
What important information can be provided by studying occupational cancers?
Identification of specific carcinogens present in various occupations
What are the six classes of carcinogens?
2) Radiations (including UV light)
4) Dietary exposures
6) Social habits
What are chemical carcinogens?
Often highly reactive electrophiles - react with nucleophilic sites in the cell like DNA, RNA, and proteins
Can be direct (chemical is the active carcinogen) or indirect (procarcinogen - metabolite of the chemical is the active carcinogen)
What are four examples of procarcinogens?
Polycyclic aromatic hydrocarbons (in cigarette smoke)
Naturally occurring carcinogens (peanut mold)
Nitrosamines and amides (nitrate preservatives)
What enzymes are responsible for metabolizing and activating most known carcinogens?
Cytochrome P450-dependent mono-oxygenases
What is one enzyme that can inactivate procarcinogens? What chemical does it act on?
Glutathione-S-transferase (GST) - inactivates polycyclic aromatic hydrocarbons
What cancer is caused by UV light?
What cancers are caused by ionizing radiation (X-rays, gamma rays)?
Leukemia, thyroid, and many others
What viruses are capable of causing cancer? Name four
HPV - cervical cancer
EBV - lymphoma
Hepatitis B and C - liver cancer
Human T-cell lymphotrophic virus-1 - leukemia/lymphoma
What parasites are capable of causing cancer? Name two
Shistosoma haematobium - bladder cancer
Opisthorchis viverrini - bile duct cancer
Name two dietary carcinogens
Aflatoxins (peanut mold) - liver cancer
Arsenic - lung and skin cancer
What are two examples of therapeutic agents that can cause cancer?
Many chemotherapeutic agents - lymphomas and leukemias
Estrogenic hormones - endometrium and breast cancer
What are six examples of cultural and lifestyle habits that can cause cancer?
1) Tobacco smoke - lung, respiratory tract, kidney, bladder, and pancreas cancers
2) Ethanol - liver and GI cancers
3) Betal quid - mouth cancer
4) Smokeless tobacco - mouth cancer
5) Chinese salted fish - nasopharyngeal cancer
6) Obesity - colon, endometrial, and breast cancers
What are the leading modifiable risk factors for cancer worldwide? Name four
1) Tobacco smoking and ethanol consumption
2) Diet low in fruits and vegetables
3) Obesity (in developed countries)
4) Unprotected sexual habits (cervical cancer)
Carcinogenesis requires two big things - what are they?
An INITIATOR and a PROMOTER
What are initiators and promoters? How do they cause cancer?
Initiators are usually agents that cause DNA damage or mutations
Promoters usually cause cellular proliferation and expand the number of cells with damage
This leads to a multi-step model of carcinogenesis
Neoplasia only occurs when initiators are administered prior to promoters
How do the statistics of childhood cancers differ from those of adults?
Rare overall (only 1% of new cancers)
Second leading cause of death before age 15
Better survival rates - 80% survive 5 years or more
Types of cancers seen are very different - adult type carcinomas are rare