While organised mammography screening programs were being gradually introduced across various countries, researchers could study the impact of screening on breast cancer mortality by comparing mortality in areas with and without screening. Now that screening has been fully implemented in most Western countries, researchers can only compare women who participate in screening with those who do not participate.
Women who do not participate in screening may seem to be a good choice as a comparison group, as they are not affected by screening. But the question is: can non-participants reflect how breast cancer mortality would have developed in women in general without the introduction of screening?
Smoking was established as a cause of lung cancer in the late 1950s. It then took another 50 years to establish that colorectal cancer was also a smoking-related cancer. However, as of 2018, a causal relationship between smoking and breast cancer had not yet been established. It may seem strange that it is taking so long to prove that smoking is a cause of all three of the most common cancers globally. Breast and lung cancer each account for 2.09 million cases annually and colorectal cancer for 1.8 million.
World Cancer Day is a global event which takes place annually on 4 February to educate and raise awareness about the disease with the aim of saving millions of preventable deaths each year. This year’s theme ‘We can. I can’ explores how everyone can do their part to reduce the global burden of cancer.