PEnile ReHABilitation After Nerve Sparing Robot-assisted Radical Prostatectomy for Prostate Cancer 2.0 (PEHAB-II)

Inclusion Criteria: Pre-screening eligibility criteria * Age \> 18 years and \< 70 years * Patients who have a penis that has developed naturally, without surgical interventions. * Histologically confirmed PCa * Scheduled for RP as primary treatment with the intention of at least a one-sided nerve-sparing procedure. * Non-metastatic disease (cN0M0) * Pre-operative erections good enough for intercourse (anamnestic) * Motivated to participate in a penile rehabilitation program Inclusion criteria To be eligible to participate in this study, a subject must meet all of the following post- operative criteria: * All of the above-mentioned pre-screening eligibility criteria * At least unilateral nerve-sparing or if available Fascia Preservation (FP) score =\>5 * A pre-diagnostic anamnestic erection that was good enough for intercourse. * A pre-diagnostic IIEF-EF\>=22 with or without PDE5i. For patients without a partner or did not participate in penetrative sex we use accumulated score of EPIC- erectile function; Q8b, Q9 and Q10 \>=83. * Willing to provide one blood sample to determine testosterone level, hemoglobin 1Ac, liver enzymes and lipid profile * Testosterone levels of at least \>=12 nmol/l, measured pre or post-operative * A signed informed consent form Exclusion Criteria: Pre-screening exclusion criteria: Regarding history of oncological treatment * Previous pelvic radiation therapy * Patients on Androgen Deprivation Therapy (ADT) * Patients with diseases that affect the red blood cells (e.g., sickle cell anaemia), blood cancer (leukaemia) or bone marrow tumors Regarding history of cardiovascular diseases * Patients with heart failure New York Heart Association (NYHA) ≥ class 3 * Patients with increased susceptibility to vasodilators include those with left ventricular outflow obstruction (e.g., aortic stenosis, hypertrophic obstructive cardiomyopathy), or those with the rare syndrome of multiple system atrophy manifesting as severely impaired autonomic control of blood pressure. * Patients with unstable angina pectoris * Patients using nitride oxide for coronary artery disease * Patients with hypotension (blood pressure \<90/50 mmHg) * Patients with recent history of stroke or myocardial infarction * Patients with diseases that affect blood clotting or causes bleeding (i.e. coagulation disorders) or prolonged erections Other pre-screening exclusion criteria: * Patients with neurological diseases; such as transient ischemic attack (TIA), Cerebrovascular accident(CVA), Parkinson, and polyneuropathy. * Allergy regarding Sildenafil * Patients who have loss of vision in one eye because of non-arteritic anterior ischaemic optic neuropathy (NAION), regardless of whether this episode was in connection or not with previous PDE5 inhibitor exposure. * Patients with severe hepatic impairment * Patients with known hereditary degenerative retinal disorders such as retinitis pigmentosa (a minority of these patients have genetic disorders of retinal phosphodiesterases). * Patients using alpha-blockers, but they may be eligible to participate after discontinuing alpha-blocker use. * The inability to speak and read in Dutch Exclusion criteria * A potential subject who meets any of the following criteria will be excluded from participation in this study: * All of the above-mentioned pre-screening exclusion criteria * \>pT3b * Adjuvant radiotherapy or hormonal therapy * Inability to use VED such as severe penile deformity causing fitting problems