Case Study
A single patient's lung tumor is diagnosed only after decades of asbestos exposure at work. This case shows the one Hill viewpoint a case study can prove well.
What is temporality?
A trial testing low, medium, and high doses of a chemotherapy drug checks whether higher doses shrink tumors more.
What is biological gradient or dose-response?
Combining smoking and lung cancer studies from many countries is the best way to check whether the link holds up everywhere.
What is consistency?
Mesothelioma is a very rare cancer almost always linked to asbestos exposure. Because the cancer type is so distinctive, early case reports pointed strongly to one cause.
What is specificity?
In a mammography screening trial, women are randomized before any follow-up begins, so we know for certain the screening happens before any cancer outcome is observed.
What is temporality?
A meta-analysis finds that a chemical is associated with a specific cancer. The epidemiological findings are supported by toxicology studies, animal experiments, pathology findings, and molecular research showing the same general biological effect.
What is coherence?
A case report on one patient's tumor can't tell you whether the same cancer-causing effect shows up in other people or populations.
What is consistency?
20,000 participants are randomly assigned to receive either a cancer-prevention intervention or placebo. After 10 years, the intervention group develops significantly fewer cases of the targeted cancer.
What is experiment?
A meta-analysis of 35 studies finds that people with high occupational exposure to asbestos have approximately 5 times the risk of lung cancer compared with those with little or no exposure. The authors argue that the large effect size strengthens the causal argument.
What is strength?
Early case reports of lung cancer in young, non-smoking women led researchers to propose a biological explanation (like an EGFR gene mutation) worth investigating further.
What is plausibility?
A new medication is being tested for cancer prevention. Researchers are particularly cautious because a chemically similar medication has previously been shown to increase the risk of certain tumors.
What is analogy?
A meta-analysis examines alcohol consumption and breast cancer and finds that risk increases progressively as consumption increases.
What is biological gradient or dose-response?