Aetiology Flashcards
Aetiology definition
The cause, set of causes, or manner of causation of a disease or condition
What are carcinogens?
Long ‘latent period’ ( dependent on carcinogen, intensity, and duration of exposure) between exposure to a carcinogenic agent & the clinical appearance of the disease = Delay in establishing cause
What are the main carcinogen groups
1.Chemicals
2.Radiation
3.Viruses
4.Hormonal status
5.Genetic susceptibility
6.Chronic irritation
7.Social factors
8.Iatrogenic factors
Chemicals
Some are direct carcinogens
•Many cause environmental pollution
•Workers in industries are at greatest risk
•Once identified, need to eliminate the hazard
•Classic example = asbestos and mesothelioma .
All asbestos has been banned in the UK since 1999, so modern products should be asbestos-free and there are strict regulations about work that may involve asbestos exposure .
Ultraviolet radiation
Significant correlation with development of Basal cell carcinoma (BCC), Squamous cell carcinoma (SCC) and malignant melanoma
•Prolonged exposure of the skin = increased risk of skin cancer
•Fair skinned = increased risk
Ionising radiation (A)
a) Occupational exposure:
•Radiation dermatitis, skin cancer and leukaemia.
•Miners of radioactive ores
•Bone sarcomas
•Painters of luminous watch dials with radium
Ionising Radiation (B)
b) Therapeutic application
•Irradiation for enlarged thymus gland → Thyroid cancers
•Ankylosing spondylitis → myeloid leukaemia
•Foetal irradiation → acute lymphoblastic leukaemia
•‘Mantle RT’ for Hodgkin lymphoma → breast cancer
Ionising Radiation (c)
c) Nuclear explosion
•Atomic bombs (e.g. Hiroshima)
•Some immediate effects – death (due to both heat and force of the explosion as well as acute radiation exposure)
•various cancers up to 40 years later (latent period)
Viruses
HIV
•HPV
•EBV
•Hepatitis viruses
Hormonal status
Fluctuations in hormone levels account for higher levels of breast cancer in women than men
•Tumours known to be hormone dependent: breast, ovary, uterus, prostate
Genetic susceptibility
Few cancers have a direct link genetically - breast, ovarian, melanoma.
•Kleinfelter’s syndrome (extra X chromosome) and male breast cancer
Chronic irritation
Mechanical factors or infection
•Oral cancers associated with ill-fitting dentures, poor oral hygiene, jagged teeth and syphilis
•Chronic conditions: ulcerative colitis, cirrhosis of the liver, polyps
Social factors
Smoking
Inactive lifestyle
Alcohol intake
Diet
Iatrogenic factor s
Immunosuppressive drugs: leukaemia and lymphomas or following organ transplant
•Cytotoxic drugs e.g. alkylating agents
•Hormonal drugs e.g. stilboestrol and oestrogen
Aetiology and NMSC
The major risk factor for skin cancer is exposure to ultra-violet radiation from the sun or sun-beds, especially for fair-skinned people as UV radiation induces DNA damage in keratinocytes.
•Exponential increase of BCCs in relation to UV exposure.
•In particular, the 290-320 nm wavelength UV (sunburn wavelength) is believed to play an important role in the formation ofBCC.
•It should be viewed as a hazard to children and adolescents, as about one quarter of lifetime exposure occurs before 18 years of age.
Aetiology SCC
Chronic to ultra violet light exposure
Common in sun-damped skin, fair skin,
Congenital diseases, oculocutaneous albinism and xeroderma pigmentosum and pre-existing lesions like Bowen’sdisease
What is xerodermapigmentosum
A rare autosomal recessive genodermatosis with a worldwide incidence of 1:250 000 live births.
•Patients have a genetic inability to repair DNA damage that has been induced by ultraviolet light.
•This manifests clinically as photosensitivity and an incidence of cSCC that is >1000 times higher than the average.
Treatment for xeroderma pigmentosun,
Treatment includes protection from ultraviolet light (avoidance, protective clothing, protective glasses, face shield, and sunscreens with a high SPF (sun protection factor).
•Due to the high incidence of skin cancer linked with xeroderma pigmentosum, patients need skin cancer surveillance every three months by a consultant dermatologist.
Other skin conditions
Actinic (solar) Keratosis
•Dry, scaly patches of skin caused by sun damage
•Xeroderma pigmentosum (XP)
•Rare genetic disorder with heightened sensitivity to UV radiation
•Psoriasis treatments
•A chronic, autoimmune mediated skin condition. (slight) increased cancer risk may be due to chronic inflammation rather that immunosuppressant drugs.
•Eczema treatment
•Minimal evidence
Other risks
A suppressed immune system
•Taking immune-suppressive drugs following organ transplant or receiving radiation treatment can lead to increased risk of skin cancer.
•Gorlin syndrome
•Also known as nevoid basal cell carcinoma syndrome
•Past radiation exposure
•Human Papilloma virus
•Birthmarks
•Chemical exposure
Patient/family Hilton
•Being diagnosed with a non-melanoma skin cancer means that you:
•have about a 10 times higher risk of a second non melanoma skin cancer
•might also be at an increased risk of developing a second primary cancer (other than skin cancer), it’s not clear why
•Most non melanoma skin cancers don’t run in families, but research has found some families seem to have a higher number than normal.
People who have a family history of melanoma have an increased risk of basal cell skin cancer (BCC).
