15250-m-cuypers

11 General introduction 1 during puberty, regulated by hormones (testosterone). A healthy prostate has the size comparable to a walnut 18 . Men from 50 years and older frequently experience problems from growth of the prostate. Usually this is a benign enlargement of the prostate, which is not caused by cancer. With Pca, there is an uncontrolled growth of the prostate glandular cells. This changes the structure of the prostate gland, resulting in enlargement of the prostate and hardening of the prostate tissue 19 . In this dissertation, when the term Pca is used, we refer to prostate cancer at a localized stage. At this stage the cancer cells are located within the prostate (stage T1 or T2; Figure 1), without progression through the prostatic capsule and into surrounding tissue (T3) or other organs (T4) 20 . Pca progression during the localized stage is usually slow, and multiple, equally effective options can be considered for treatment, as well as the option not to treat immediately, as the tumor may not progress to an advanced stage at all 14 . Figure 1. Location of the prostate and tumor stages. © Cancer Research UK / Wikimedia Commons (CC BY-SA 4.0) Figure 2. Three dimensional image of a prostate with cancer, after needle biopsy 21 Growing number of Pca patients In 1970, prostate specific antigen (PSA) was discovered as an indicator for Pca 22 . The level of PSA can easily be measured with a simple blood test. An elevated PSA level might be an indication for Pca and reason for further investigation, such as a rectal examination, imaging, and prostate biopsy (Figure 2). During the 1990’s, PSA testing became common practice, and consequently, Pca detection has increased significantly 23 . As Pca mostly