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AJR September 2018

Aytekin Oto
University of Chicago
Chicago, IL

“MRI Findings After MRI-Guided Focal Laser Ablation of Prostate Cancer”

Multiparametric MRI can provide value by highlighting changes in the prostate following MRI-guided focal laser ablation (FLA), according to a study published in the September issue of AJR. This study sought to describe the quantitative and qualitative findings of multiparametric prostate MRI performed after MRI-guided focal laser ablation of prostate cancer. The results published in the September 2018 issue of AJR showed that multiparametric MRI can reveal postablation changes in the prostate and can be a valuable tool for monitoring patients who have undergone MRI-guided focal laser ablation.

A total of 27 consenting patients met the study inclusion criteria, which included but were not limited to the presence of clinical category T1c–T2a prostate cancer with a Gleason score of 7 or less, having undergone prostate biopsy before and after focal laser ablation, and having undergone MRI before ablation, immediately after ablation, and 3 and 12 months after ablation. Signal changes were evaluated both qualitatively and quantitatively and were then correlated with the results of subsequent biopsy performed at 3 and 12 months after ablation.

MRI performed immediately after ablation revealed a hypovascular defect in the ablation zone, with patchy or bandlike decreased T2 signal most commonly noted at 3 months (in 66.7% of patients) and T2 scarring observed in most patients (66.7%) at 12 months. Patchy or bandlike decreased apparent diffusion coefficient signal and scar-like changes were most prevalent at 3 months after ablation (50.0% of patients), and these features remained the most commonly observed findings at 12 months after ablation (27.8% of patients). At 12 months after ablation, 10 patients were found to have recurrent tumor, with three patients found to have persistent cancer when biopsy was performed at the ablation site. All postablation biopsy cases with positive results showed suspicious T2 and apparent diffusion coefficient characteristics, which were considered to be a well-defined nodular intermediate signal on both of these sequences. Two of the patients for whom positive biopsy findings were noted had focal enhancement of the ablation zone. A significant reduction in the forward volume transfer constant after ablation was found at the ablation site on follow-up examination.

In this Q&A, Oto discusses the authors’ ideas behind the study and the outlook for further research.

What is the background for this study? How did you and your co-authors come up with the idea?

Oto: Focal therapy is a rapidly emerging treatment technique for prostate cancer. MR-guided laser ablation is one of the leading focal therapy techniques that is currently clinically used. Imaging is critical for the success of focal therapy at every step including patient identification, treatment planning and follow-up of patients. For other therapies of prostate cancer, serum PSA levels are used as biomarker for detection of prostate cancer following therapy. However, after focal therapy of prostate cancer, since non-cancerous part of prostate is left behind and PSA can also be produced by healthy prostate, the ability of serum to PSA to detect prostate cancer recurrence is very limited. Therefore, post-therapy imaging is critical for the follow-up of these patients after focal laser ablation.

There is limited to no information in the literature regarding post-laser ablation MR findings. Our data is particularly important since this is part of a prospective trial.

At the Sanford J. Grossman Center of Excellence in Prostate Imaging and Image Guided Therapy at the University of Chicago, we are the pioneers in MR guided Focal Laser Ablation and successfully completed Phase I and NIH funded Phase II trials and now offer this procedure as standard of care at our institution.

What should readers take away from your article?

Oto: MR imaging can be used for follow-up of patients after focal laser ablation as part of a follow-up algorithm. Certain MR findings such as focal early enhancement on DCE-MR can be a finding for recurrent prostate cancer. MR can also allow detection of cancers within the prostate that can develop at sites other than the treated cancer during follow-up.

It is important for radiologists to be aware of the expected MR findings after laser ablation as well as the findings that are suspicious for cancer. The value of before first year as a follow-up study is limited due to extensive post-ablation changes.

What recommendations do you have for future research as a result of this article?

Oto: Validation of these findings in larger future prospective studies is warranted.

Is there anything else you would like to add?

Oto: Our study is a result of a multi-specialty team work. I would like to thank all of our team members for their dedication and NIH for supporting our research.


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