The global burden of cancer is high and continues to increase: the annual number of new cases was estimated at 14.1 million in 2012 and is expected to reach 22.2 million by 2030 (Ferlay et al., 2015). With current trends in demographics and exposure, the cancer burden has been shifting from high-resource countries to low- and medium-resource countries.
Prevention of cancer is one of the key objectives of the International Agency for Research on Cancer (IARC). Cancer prevention can be achieved by primary prevention – aimed at preventing the occurrence of cancer – or by secondary prevention – aimed at diagnosing cancer sufficiently early to reduce related mortality and suffering.
Screening and early clinical diagnosis are the principal instruments of secondary prevention of cancer and a fundamental component of any cancer control strategy. Screening may enable detection of cancer sufficiently early that cure and resulting reduction in mortality and having the disease are realistic possibilities given suitable treatment. Screening for some cancers, such as cervical or colorectal cancer, may also detect precancerous lesions, effective treatment of which can prevent occurrence of cancer.