Early diagnosis aims to detect cancer in its early stages when it is potentially curable. This can apply not only to people who already have symptoms of a given cancer, but also to those who, not having any symptom, are subject to known risk factors that justify this approach.
This supposes, in particular, an “increased awareness of the first signs of cancer among physicians, nurses and other health care providers, as well as among the general public”, stresses the (WHO) on its website.
Screening, on the other hand, “consists of testing [populations of] healthy individuals to identify those having cancer before any symptoms appear”, writes the WHO.
Early diagnosis programmes, such as the one existing at the Champalimaud Clinical Centre (CCC), thus aim at reducing the proportion of patients who are diagnosed at a late stage, which is crucial in terms of prognostic and outcomes.
Unfortunately, not all cancers are amenable to early diagnosis because only at a late stage do their symptoms become manifest. This is the case with pancreatic cancer and ovarian cancer, for instance. Actually, early cancer diagnostic is really feasible only for certain cancers: breast, cervix, mouth, larynx, colon and rectum, and skin.
An aside: because of this, the CCC provides a more complete service, a sort of “mix” between the two early detection strategies: a Risk Assessment and Early Diagnosis Programme. This programme includes initial consultations – for healthy individuals – “that pay special attention to their gender, age, lifestyle, clinical history, and genetic risk, in order to identify their most significant risk factors”. A follow-up consultation is then scheduled to discuss the results and define an action plan based on the individual’s identified risk factors, “which may include lifestyle recommendations or define a calendar to perform regular medical exams” – something more akin to screening.
Screening, as already mentioned, is normally performed at the level of populations essentially composed of healthy people, usually under public health programmes/campaigns. It consists of the use of relatively simple tests that are able to detect cancer or pre-cancerous lesions and can be performed on large numbers of people. Mammograms for breast cancer and Papanicolaou smears for cervical cancer are among the best-known of these tests.
However, as summarised by the WHO, screening tests have drawbacks such as: falsely positive results that lead to additional testing, invasive diagnostic procedures and patient anxiety; falsely negative results that provide false reassurance; and overdiagnosis, which leads to unnecessary treatment of preclinical cancers that might never cause symptoms nor become a serious health threat.
That is why this international agency does not recommend mammography screening in women less than 50 years of age and only advocates mass population screening for cervical, breast and colorectal cancer. The Liga Portuguesa Contra o Cancro also recommends starting mammogram testing only in women from 50 years on.
By Ana Gerschenfeld, Health & Science Writer of the Champalimaud Foundation.
Reviewed by: Professor António Parreira, Clinical Director of the Champalimaud Clinical Center.