Over the last 20 years, the number of tumours diagnosed has grown steadily, not only due to population growth, but also thanks to early cancer detection techniques and increased life expectancy.
Although the risk of developing cancer has increased, fortunately the risk of cancer mortality has been decreasing over the last twenty years. The behaviour, prognosis and treatment of different types of cancer, even within the tumour’s different stages of development, are highly variable.
Regarding cancer diagnoses, a distinction shall be made between screening tests and diagnostic tests.
Cancer screening tests are used to detect the possibility of the disease’s presence before symptoms even appear. In women, two of the most commonly used screening tests are the Pap test (or Pap smear) to detect cervical cancer, and the mammogram to detect breast cancer. In men, prostate-specific antigen (PSA) blood levels are used to detect prostate cancer.
The diagnostic testsare carried out when there is already a suspicion of cancer.
In vivo and in vitro Cancer Diagnostics
As with symptoms, the tests used to diagnose cancer vary depending on the type of tumour suspected. However, diagnostic tests usually consist of a physical examination followed by various imaging procedures, such as an X-ray, ultrasound or computed tomography (CT) scan. Nuclear medicine, which employs radiopharmaceuticals for primarily diagnostic (imaging) purposes, may also be used.
Although these tests can show the presence, location and size of an abnormal mass, they cannot confirm that the cause of these masses is cancer. To confirm the cancer diagnosis, a sample of the tumour (biopsy) needs to be taken and analysed under a microscope at a later date. Generally, the sample should be a piece of tissue, although sometimes it is appropriate to test blood by performing a liquid biopsy.
Five medical specialties are involved in the diagnosis of cancer: