LAUSR

DOI:10.1097/MOU.0000000000000552 We are delighted to present this special issue of ‘Current Opinion in Urology’ addressing several contemporary topics of focal therapy for prostate and kidney cancers. Over the past two decades, we have observed the changing landscape of prostate cancer and renal tumors. In the era of prostate cancer screening, there has been a stage migration and shift toward smallvolume low-to-intermediate-risk prostate cancer [1]. Although radical treatment is still the most common management strategy for localized prostate cancer, its associated comorbidities remain a great concern to patients [2,3]. Active surveillance, on the other end of the spectrum, is the least invasive management strategy for low-risk to some favorable intermediate-risk prostate cancers. However, as many as 20% of patients under active surveillance protocols may ultimately select radical treatment because of disease reclassification and/or patient anxiety [3,4]. In the era of ‘organ conservation’ cancer surgery, focal therapy for prostate cancer offers targeted treatment of the clinically significant cancer foci with preservation of the nonmalignant portion of the prostate gland and genitourinary function. The ‘index lesion theory’ is a fundamental concept of focal therapy. Despite the multifocal nature of prostate cancer, the index lesion defined as the largest lesion with the highest Gleason score, characteristically drives the oncological outcome of the individual’s prostate cancer. In fact, concordance between the genomic sequencing of a high-grade cancer focus and metastatic sites suggests that the index lesion can be the primary source of metastasis [5,6]. Similarly, the incidence of primary renal tumors is rising largely because of an increasing use of imaging modalities for the evaluation of unrelated conditions or nonspecific symptoms. This incidental, often asymptomatic diagnosis is associated with a stage migration, such that more than a half of all renal tumors are detected as stage I (i.e. organ confined renal mass of 4 cm in the greatest diameter) [7]. Nephron-sparing modalities, ranging from active surveillance to partial nephrectomy, are the cornerstone of management for these small renal masses. Since its introduction over the past 20 years