The goal of this feasibility study is to test a newly developed, multicomponent prehabilitation intervention to patients with prostate cancer, to improve their resilience to treatment side-effects. The main questions it aims to answer are: * Are patients and their close relatives willing to take part in prehabilitation? * What is the acceptability and feasibility of the prehabilitation intervention, seen from the perspectives of patients, their close relatives, and healthcare professionals? * Are the planned data collection methods feasible, and are there indications of a clinical effect? Participants will: * Take part in 12 weeks of physical exercise training * Attend a 4-day residential prehabilitation intervention, where they receive education and do exercises. After 12 weeks, it is possible to take part in a voluntary follow-up session. * Patients will respond to questionnaires about their health, symptoms, and quality of life. Patients and their close relatives will attend a group interview. Patients will also complete an exercise diary and brief physical tests