In 2009, Atri et al. [32] introduced the application of CEUS-guided LITT. They treated a patient with biopsy-proven, solitary focus, low-risk PCa, visualized on mpMRI prior to the procedure. During and after photothermal therapy treatment, they observed large hypocontrast regions surrounding the treatment fibers, indicating the presence of an avascular lesion. The lesion they measured using CEUS also corresponded to tissue devascularization seen on a gadolinium (Gd)-enhanced MRI lesion 1 week after the procedure.

One of the first reported phase 1 studies assessing the feasibility of using a CEUS-guided focal laser with MRI was by Lindner et al. in 2009 [37]. They looked at 12 patients, including a patient from the 2009 Atri et al. study [32], with biopsy-proven low-risk PCa (T1c or T2a, PSA <10 ng/ml, Gleason score ≤6, only 1 of 12 cores <30 % cancer following transrectal ultrasound (TRUS)-guided biopsy) that underwent interstitial photothermal ablation. MRI was used to confirm and target the lesion, and a 3D ultrasound was fused to this to help guide the laser. Out of this cohort, 3 patients complained of perineal discomfort, 2 developed mild hematuria, 2 had hematospermia, and 1 complained of fatigue. There was no reported decrease in mean urinary or sexual function scores at 1, 3, and 6 months postoperatively. TRUS-guided 10-core systematic prostate biopsies performed 3–6 months after ablation showed 6 patients (50 %) had completely negative biopsies, 2 patients had a tumor found on the contralateral untreated side, and 4 patients had a residual tumor in previously treated areas. Of these 4 patients, 2 were found to have minimal disease on follow-up biopsy, and 2 were found to have cores greater than 50 % of Gleason 6 disease. This same group also performed a study of 4 patients who underwent LITT followed by RP in 2010 [38]. They correlated MRI-calculated ablated volume to the volume of homogenous necrosis seen on whole-mount histology. Their results showed there was a very good correlation (r = 0.89) suggesting that post-ablation MRI could be a useful tool in determining the extent of actual tissue ablation.

One of the initial experiences in using real-time MRI guidance during LITT was performed by Raz et al. in 2010 [25]. MRI guidance allowed for improved visualization of the target, more accurate direction of the laser fiber, real-time monitoring of the ablation site and surrounding tissue, as well as immediate feedback on the extent of the treatment. The patients from this study were discharged without complications, and preservation of the neurovascular bundles was noted. There were also no adverse effects noted after 1 month of treatment.

Woodrum et al. in 2010 [39] also initially explored the feasibility of performing transperineal LITT for focal targets in the prostate using real-time MRI guidance. Previous studies had been focused on 1.5 T field strengths, but this study demonstrated the practicality of a 3.0 T MRI, which offered greater spatial and temporal resolution. They were able to verify that a perineal guidance grid allowed for accurate needle placement through a transperineal route at the appropriate depth in the prostate. Furthermore, they were able to correlate the gross appearance of the ablation zone to the temperature mapping estimates.

In 2011, Woodrum et al. [40] explored the use of 3.0 T MR focal laser thermal ablation therapy within the prostate bed in PCa recurrence. They reported a study in which they used LITT with real-time MR temperature mapping using the PRF shift to treat a patient with a documented recurrence after RP. The case was successful in treating the patient’s recurrence with a decrease in PSA from 2.0 to 0.42 ng/ml at 2 months after therapy. Early follow-up showed no posttreatment incontinence, rectal wall injury, or other complications.

In 2013, Oto et al. [41] published the results of their phase 1 trial (federally registered NCT01192438) evaluating the safety and feasibility of MRI-guided focal laser therapy in men with clinically low-risk PCa (clinical stage T1c–T2a, PSA <10 ng/ml, Gleason ≤7, minimum of 12 biopsy cores with 3 or fewer containing cancer, no single biopsy with >50 % tumor involvement, and a suspicious lesion visible on MRI corresponding to the biopsy site). In total, 9 patients were treated with 8 having Gleason grade 6 cancer and 1 having grade 7 cancer. No major complications or serious adverse events after ablation occurred. MR imaging-guided biopsy of the ablation site was performed at 6 months follow-up. This revealed benign prostate in 7 patients and Gleason grade 6 cancer in 2. A retrospective review of the ablation images were performed showing that the lesion site was not completely covered by the ablation zone for the 2 patients with positive findings at follow-up biopsy. Quality-of-life (QOL) surveys were recorded at baseline and at 1, 3, and 6 months post-ablation. The study reported no statistically significant change from baseline in sexual function or urinary symptom assessments.

Lindner et al. also updated their phase 1 study to 38 men in 2013 continuing to show minimal complications after a year of posttreatment follow-up. A concerning outcome in this study was that 26 % of men treated showed a positive biopsy outside the ablated region at 4 months follow-up. This finding stresses the need for larger multi-institutional studies with longer follow-up to further elucidate the efficacy and side effect profile of focal therapies [42].