Marieke van Son

69 FOCAL SALVAGE TREATMENT: A NARRATIVE REVIEW CURRENT FOCAL SALVAGE SERIES Today, focal salvage treatment of radiorecurrent prostate cancer is performed with a variety of techniques: focal cryotherapy [73-75], focal HIFU [76], focal brachyther- apy (both low-dose-rate [77,78] and high-dose-rate [79-81]) and, in smaller series, stereotactic body radiation therapy (SBRT) [82,83]. The extend of ablation differs per ablation method and between series, ranging from ultrafocal to hemi- and subtotal ablation. Focal cryotherapy usually entails hemi-ablation by achieving a lethal freez- ing temperature of –40 °C in the prostate lobe containing the cancer. Focal HIFU can be hemi-ablation or quadrant ablation (one half of a lobe), using focused ultrasonic waves for tissue destruction by means of thermal, mechanical and cavitation effects. With brachytherapy, ultrafocal ablation can be achieved by administering radiation to a small target volume, using the steep dose fall-off with distance from the radiation source. Iodine-125 seeds are used for low-dose-rate brachytherapy, delivering a pre- scribed dose of 144-145 Gy. High-dose-rate brachytherapy delivers radiation from an Iridium-192 source through temporarily implanted catheters, which allow for dose painting by varying the dwell positions and times of the radiation source. High-dose- rate schedules vary from 18-19 Gy in a single dose to 27 Gy divided over two implants. CyberKnife-based SBRT has been performed with dose schedules between 30-35 Gy in 5 fractions. While this technique offers a high degree of conformity, it is also likely to increase the integral dose to the surrounding healthy tissues. Furthermore, without real-time MRI-guidance, planning target volume (PTV) margins for correction of intra- fraction motion remain necessary to avoid geographical miss. Different focal ablation methods have varying limitations with respect to tumor recurrence location: HIFU is less suited for treating anterior-located lesions due to insufficient length of most devices, while cryotherapy can be less effective in the apical and peri-urethral region due to organ-protective warming tools. With brachytherapy it is usually possible to cover all sides of the prostate [84,85]. Studies that report 5-year bFFS seem to reach an approximate 50% rate [86], which is comparable to whole-gland salvage series. Only one study presented a direct com- parison between focal and whole-gland using cryotherapy: 5-year bFFS rates were 54 and 86%, respectively [73]. However, differences in patient characteristics and primary radiation schedules make it hard to interpret these results. Though most literature comes from relatively recent studies, patient selection methods are often already out- dated. Exclusion of metastatic disease was often performed with either CT or MRI for nodal assessment, bone scintigraphy for bony disease and, in some series, PET/CT in a small number of patients. A modern multimodal radiologic approach with mp-MRI and (68)Ga-PSMA-PET/CT outperforms the other modalities in selecting patients with true localized, non-metastatic recurrence [44,87]. In the future, better patient selection could therefore improve oncologic outcomes of focal salvage series even further. Follow-up times are still too short to assess the impact of focal salvage treatment in terms of 4