Conceptual basis for focal therapy in prostate cancer

The proportion of men with low- to intermediate-risk prostate cancer is rising with the increasing use of formal and informal prostate-specific antigen screening. The risk-to-benefit ratio of radical therapy is large with many men suffering genitourinary side effects compared with the small degree of cancer control that they derive from surgery or radiotherapy. On the other hand, the current alternative, active surveillance, carries risk of progression as well as some psychological and healthcare burdens. Focal treatment may be an acceptable alternative: in aiming to destroy only the areas of prostate cancer, focal therapy could deliver cancer control while at the same time avoid damage to surrounding structures. This may reduce incontinence, impotence, and rectal toxicity. Improvements in localization of cancer such as template transperineal prostate-mapping biopsies as well as state-of-the-art imaging such as multiparametric MRI and novel ultrasound-based tissue characterization tools have made the delivery of focal therapy possible. Minimally invasive ablative technologies such as cryotherapy, high-intensity focused ultrasound, photodynamic therapy, photothermal therapy, or radiofrequency interstitial tumor ablation can precisely treat to within a few millimeters. Early studies evaluating focal therapy have found a lower side-effect profile with acceptable short- to medium-term cancer control rates. If these promising results are confirmed in future prospective trials, focal therapy could start to challenge the current standard of care.