Image guidance for focal therapy of prostate cancer

Focal therapy is an appealing strategy for any tumor and in time may prove to be a valuable treatment option for low-risk, carefully selected prostate cancer (PCa) patients. In an era where active surveillance is now considered a viable option for low-risk PCa patients, it is conceivable that organ-sparing treatments could also become an established option. The aim of focal therapy is to achieve long-term cancer control with minimal morbidity yet without the side effects of radical therapy. Although lacking in evidence, it remains intuitive that if we treat the smallest possible region of the prostate where to ensure cancer control by ablation (laser, cryotherapy or another ablative source), then there is less potential for untoward side effects. Thus, we believe the ultimate goal in focal therapy is to target specifically the cancerous site while ablating it and the smallest zone of normal prostate tissue around it to obtain cancer control. To achieve this goal, one is dependent on high-quality imaging to: locate the cancerous lesion and have it assist in guiding the ablative modality toward the lesion; monitor the ablation in real time; accurately assess the extent and totality of the ablation post-treatment and finally be used to follow-up and monitor the prostate in search of a recurrence of cancer in the treated area or the development ion new zones. This review seeks to discuss such issues focusing on imaging modalities as they relate to focal therapy of PCa.