Timo Soeterik

19 General Introduction and Thesis Outline the outcomes of AS in patients not fulfilling one or more of the traditional AS inclusion criteria. 44,49 More data are urgently needed to assess whether the inclusion criteria can be expanded. To enable timely detection of disease progression, intensive follow-up schemes are used to ensure the safety of AS. Although different AS follow-up protocols have been described, follow-up is generally characterized by periodical repeat prostate biopsies (every 1-3 years) and PSA monitoring (every 3-6 months) to assess if the disease progresses to a stage for which active treatment is indicated. 46 Strict adherence to AS follow-up protocols requires commitment of the urologist and the patient, especially since prostate biopsies are associated with pain, hematuria and an increased risk of urinary tract infections. 50 When applied in clinical practice, AS follow-up may not be compliant with current AS protocols. For instance, Loeb and colleagues evaluated the frequency of PSA testing and repeat biopsies in 5,192 patients on AS, and concluded that although over 80% of patients had 1 or more prostate specific antigen tests per year, fewer than 13% underwent prostate biopsy beyond the first 2 years follow-up. 51 Question remains whether this lack of compliance results in unfavourable outcomes for the patient, or if lower-intensive follow-up is safe in specific patient subgroups. To conclude, although prior studies have demonstrated that AS is an effective and safe strategy to reduce overtreatment of prostate cancer, it remains to be determined if AS is also a safe when applied outside the strict trial setting. Areas that remain to be explored include the compliance with AS protocols regarding patient selection and follow-up intensity in real-world practice. In addition, it should be further evaluated in which patients, and to what extent, follow-up intensity and invasiveness can be reduced to further minimize treatment-related burden. Lastly, it should be established if selection for AS can be widened, by evaluating the outcomes of AS in patients not fulfilling all standard eligibility criteria. SANTEON The Santeon Prostate Cancer Value Based Healthcare programme The Santeon consortium consists of seven hospitals including OLVG Amsterdam, Maasstad Hospital Rotterdam, St. Antonius Hospital Utrecht/Nieuwegein, Canisius Wilhelmina Hospital Nijmegen, Catharina Hospital Eindhoven, Martini Hospital Groningen and the Medisch Spectrum Twente Enschede (in close collaboration with the Hospital Group Twente Almelo/Hengelo). Within the context of the Santeon Prostate Cancer Value Based Healthcare (VBHC) project, the hospitals have worked together intensively for over 10 years, comparing clinical and patient-reported outcomes. Since the initiation of the VBHC project, a data-infrastructure has been organized. The designed data-infrastructure facilitates short-cyclic feedback loops to improve clinical outcomes. In addition, the collected data 1