Marieke van Son

8 CHAPTER 1 The present thesis constitutes an investigation of the role of focal therapy in the treat- ment of prostate cancer. Considering the complexity of the topic, this introduction offers a comprehensive insight into all aspects of the disease including the current established treatment options, before zooming in on the concept and rationale of focal therapy. The aim is to provide a wide basis for a well-founded vision on its potential. Epidemiology Prostate cancer is the second most common cancer in men (after skin cancer), affecting 1 in 9 men over the course of their lifetime(1). Incidence rates increased rapidly in the early 1990s (Figure 1) due to a screening surge using prostate specific antigen (PSA) testing to detect latent prostate cancers in asymptomatic men(2). In more recent years, incidence rates have declined because of recommendations against the routine use of PSA-screening, although this remains controversial. Main arguments against screen- ing involve the risk of over-diagnosis of indolent cancers and unnecessary treatments which carry a financial, emotional and physical burden(3). Main arguments in favor of screening involve the risk of delaying the diagnosis of a more aggressive or advanced prostate cancer, diminishing survival rates substantially(4, 5). Although the peak in PSA-testing in the early 1990s was accompanied by a relative increase in prostate cancer-specific mortality (Figure 2), which is most likely explained by the larger pool of evident prostate cancer patients at the time, the steady decline of mortality rates after- wards shows no clear survival advantage for population-wide PSA-screening. Current guidelines recommend the decision to screen should be an individual one, balancing benefits and harms based on individual characteristics and patient preference(6, 7). Figure 1 – Trends in age-standardized cancer incidence rates among males in the United States. Image adapted from: Siegel et al., 2020(2)