ObjectivePatients with potentially indolent prostate cancer (PC) can be managed with active surveillance (AS). Our objective was to analyse how anxiety and distress develop in men with untreated PC and whether highly anxious men quit AS. MethodsOne hundred and fifty Dutch patients who opted for AS in the Prostate cancer Research International: Active Surveillance Study were invited to participate in an additional prospective, longitudinal quality of life (QoL) study within 6months after diagnosis. Participants completed questionnaires with validated measures on anxiety and distress at inclusion (t=0), 9 (t=9) and 18 (t=18) months after diagnosis. We assessed changes in scores on depression (Center for Epidemiologic Studies Depression (CES-D) scale), generic anxiety (State-Trait Anxiety Inventory (STAI-6)), PC-specific anxiety (Memorial Anxiety Scale for Prostate Cancer (MAX-PC)) and decisional conflict (Decisional Conflict Scale (DCS)) about patients' treatment choice between t=0, t=9 and t=18 using repeated measures analysis. ResultsResponse rates for patients still on AS at t=0, t=9 and t=18 assessments were 86%, 90% and 96%, respectively. Nine patients (7%, 9/129) between t=0 and t=9 and 33 of 108 patients (31%) between t=9 and t=18 stopped AS, mostly (86%) because of protocol-based reasons. CES-D, total MAX-PC and DCS scores did not change significantly (p>0.05) when comparing t=18 with t=9 and t=0 scores, but generic anxiety (STAI-6; p=0.033) and fear of disease progression (sub-score of the MAX-PC; p=0.007) decreased significantly. These differences, however, were clinically modest (0.089 SD and 0.281 SD). Overall, six of 129 men (5%) discontinued AS because of anxiety and distress. ConclusionsWhen men with low-risk PC are managed with AS, fear of disease progression and general anxiety decreased, and only few may discontinue AS because of anxiety and distress. This suggests that negative QoL effects are limited in men with favourable clinical characteristics who opted for AS. (Registered trial number, NTR1718) Copyright (c) 2014 John Wiley & Sons, Ltd.