Group items tagged

“Intrinsic processes” include those that result in mutations due to random errors in DNA replication whereas “extrinsic factors” are environmental factors that affect mutagenesis rates (such as UV radiation, ionizing radiation, and carcinogens

intrinsic factors do not play a major causal role.

intrinsic cancer risk should be determined by the cancer incidence for those cancers with the least risk in the entire group controlling for total stem cell divisions

if one or more cancers would feature a much higher cancer incidence, for example, lung cancer among smokers vs. non-smokers, then this most likely reflects additional (and probably extrinsic) risk factors (smoking in this case)

Particularly, for breast and prostate cancers, it has long been observed that large international geographical variations exist in their incidences (5-fold for breast cancer, 25-fold for prostate cancer)14, and immigrants moving from countries with lower cancer incidence to countries with higher cancer rates soon acquire the higher risk of their new country

Colorectal cancer is another high-incidence cancer that is widely considered to be an environmental disease17, with an estimated 75% or more colorectal cancer risk attributable to diet

melanoma, its risk ascribed to sun exposure is around 65–86%

non-melanoma basal and squamous skin cancers, ~90% is attributable to UV

75% of esophageal cancer, or head and neck cancer are caused by tobacco and alcohol

HPV may cause ~90% cases in cervical cancer23, ~90% cases in anal cancer24, and ~70% in oropharyngeal cancer

HBV and HCV may account for ~80% cases of hepatocellular carcinoma

H pylori may be responsible for 65–80% of gastric cancer

While a few cancers have relatively large proportions of intrinsic mutations (>50%), the majority of cancers have large proportions of extrinsic mutations, for example, ~100% for Myeloma, Lung and Thyroid cancers and ~80–90% for Bladder, Colorectal and Uterine cancers, indicating substantial contributions of carcinogen exposures in the development of most cancers

onsistent estimate of contribution of extrinsic factors of >70–90% in most common cancer types. This concordance lends significant credibility to the overall conclusion on the role of extrinsic factors in cancer development