Marieke van Son

178 CHAPTER 10 To facilitate standardized evaluation of treatment outcomes, an international multidis- ciplinary consensus panel used the modified Delphi method to reach consensus on ter- minology and adequate post-treatment follow-up(6). They recommended regular PSA- checks (every 3 months in the first year and every 6 months thereafter), multiparametric (mp)-MRI after 6 and 18 months, systematic biopsy combined with targeted biopsy of the treated area after 6-12 months, and functional outcome assessment starting 3-6 months after treatment. In terms of terminology, the panel suggested using the term “focal therapy” to describe guided ablation of an image-defined, biopsy-confirmed lesion with a safety margin surrounding it. All strategies aiming to treat a standardized anatomic part of the gland should be referred to as “partial gland ablation” (Figure 1). Even the definition of success after primary focal therapy is controversial(7). For patients, the most relevant measure of success is durable disease control, although there are several ways to define this. Among the available hard endpoints there are short-termmeasures such as presence or absence of positive cores on post-treatment biopsy, and long-term endpoints such as metastatic disease on imaging or death. A more common mid-term endpoint is biochemical disease-free survival, traditionally used as surrogate endpoint for treatment success in whole-gland treatment studies. For radical prostatectomy, the American Urological Association (AUA) and the European Association of Urology (EAU) have recommended a PSA threshold >0.2 ng/mL to define biochemical failure(8, 9), whereas radical radiotherapy uses the American Society for Therapeutic Radiology and Oncology (ASTRO) Phoenix definition of PSA nadir+2(10). With primary focal therapy, defining such a threshold is problematic due to the fact that (substantial) parts of the gland are left untreated and PSA may vary according to the ablative technology, amount of tissue treated, and amount of residual tissue that remains. Because PSA could be the expression from both malignant and benign prostate tissue, the target level after focal therapy is highly individual. A recently pro- posed definition for treatment success is percentage PSA reduction after treatment, with a PSA reduction of >90% predicting a 20% chance of patients needing additional treatment within 5 years within the studied cohort(11). An advantage of primary focal therapy is that new (or residual) lesions with clinically significant cancer arising after treatment may be re-treated, potentially again with few undesirable genitourinary and gastro-intestinal side effects. Although there are no guidelines for the management of patients with localized recurrence after primary focal therapy, all therapeutic options are theoretically possible, including radiotherapy, surgery, repeat focal therapy or even active surveillance(12, 13). Whether initial focal therapy jeopardizes the safety and oncological outcomes of subsequent treatment remains largely unknown, with the current evidence being limited to a few retrospective series(14, 15). Repeat focal therapy seems possible, although reports on efficacy remain scarce, with available studies describing either a small proportion (1.5%) of patients receiving focal repeat ablation(16) or refraining from specifically addressing functional and oncological outcomes for the repeat procedures(17). For patients in whom repeat focal therapy is deemed unfeasible, for example due to multifocal or extended disease,