Aetiology Flashcards
How has incidence varied over the last 50Y.
Overall risk relatively unchanged
Incidence of specific cancers have altered.
Changes too rapid to be explained by genetics - change in behaviour / environment. (Migrants and hosts)
What are the hormonal risk factors for breast cancer?
Hormonal (early menarche, late menopause).
Oral contraceptives
HRT (oestrogen only - adding progesterone reduces endometrial cancer risk but increases breast cancer risk).
Reproductive behaviour (age & breastfeeding).
What genetic factors contribute to colorectal cancers?
FAP - rare dominantly inherited syndrome –> high risk of colon cancer at young age (mutations in APC gene - C5)
Hereditary non-polyposis - ~5% CRC & due to mutations in DNA mismatch repair genes.
How is H.Pylori linked to stomach cancer?
–> chronic atrophic gastritis
infection prevalence increased by overcrowded living, large families, poor hygiene, low socio-economic status.
Regional strain differences are important (cage/VacA-+ve strains carry highest risk)
Aside from H. Pylori, what other factors contribute to stomach cancer?
High salted foods
Nitrates & nitrites in processed meats - react in stomach with secondary amines –> nitrosamines
How is dietary fibre thought to decrease colon cancer risk?
Decreases transit time and stool weight
Dilutes carcinogens
SCFAs induce apoptosis
Decrease in intraluminal pH inhibits secondary bile acids which are carcinogenic.
How is meat thought to increase CRC risk?
Heterocyclic amines, polycyclic amines formed during cooking are carcinogenic.
Iron increases ROS - increases cell proliferation.
Haem iron = increases endogenous NOC production.
Why is it believed that incidence has increased since 70’s?
Longer lives
Detection and awareness
Recording and diagnosis
Decreasing mortality.
How is salt thought to induce stomach cancer?
Damage stomach mucosa –> inflamm response
Increase DNA synthesis and increase cell proliferation.
Reduce DNA repair
Increase vulnerability to carcinogens.
