Letter to the Editor: “MRI targeted single fraction HDR Brachytherapy for localized Prostate Carcinoma: a feasibility study of focal radiation therapy (ProFocAL)”

by Jonathan Sussman, Connor Hoge, Abhinav Sidana (Abhinav.sidana@uc.edu)

MRI targeted single fraction HDR Brachytherapy for localized Prostate Carcinoma: a feasibility study of focal radiation therapy (ProFocAL)

Dear Editor,

We found the recent article by Fischbach et al on focal MRI-guided high-dose-rate brachytherapy for prostate cancer (CaP) of great interest as it investigates a new and promising modality for focal therapy of localized CaP [1]. In patients with low or intermediate-risk disease, the definitive treatments of CaP, such as whole gland radical prostatectomy and external beam radiation therapy, were found to have marginal survival benefit compared to active surveillance [2]. This is why focal therapy, which localizes and destroys cancer in only the region of interest, serves as an intriguing treatment option for patients with low-risk and intermediate-risk disease while preserving genitourinary function [3].

We commend the authors for demonstrating the feasibility and workflow of MRI-guided brachytherapy as another focal therapy modality for localized CaP. The study clearly demonstrated safety while preserving quality of life in all 9 enrolled patients. It is promising that of the patients receiving targeted brachytherapy, many of whom had lesions near the prostatic apex, only one patient experienced post-interventional hematuria, and even that was mild and self-limiting [1].

However, we would like to highlight a couple of points here. Firstly, being a feasibility study, this study involved a very small sample size of 9 patients, out of which only 4 patients got repeat biopsy. Also, there is reduced reliability of MRI to diagnose CaP after radiation therapy due to diffusely decreased T2 signaling [4]. The study hinges on the assumption that prostate-specific antigen (PSA) level and imaging can accurately detect recurrence in these patients when in reality, both may suffer from lower negative predictive value compared to treatment naïve setting, thus warranting repeat biopsy for documentation of oncologic efficacy. Thus, an estimate of efficacy of such treatment strategy is undetermined and only larger and longer-term efficacy studies with repeat biopsies will truly establish the safety and role of this modality for focal therapy of CaP. We also wanted to emphasize that targeted brachytherapy could serve a great purpose in patients with apical CaP. Patients with lesions in the apical aspect of CaP present a challenge for focal therapy using thermal ablative modalities like cryoablation and high intensity focused ultrasound due to the risk of thermal damage to the urethral sphincter and ensuing risk of urinary incontinence. Targeted brachytherapy would present a safer option for such patients with likely reduced risk of damage to urinary sphincter and urinary incontinence.

While there are still several questions that warrant further investigation before considering targeted brachytherapy an effective treatment option for localized CaP, this study demonstrates safety and feasibility of the procedure and we commend authors for this important study. There is no doubt that focal therapy holds exciting advantages in the treatment of CaP. Adding another efficacious modality to a physician’s armamentarium would allow further individualization of cancer therapy and ultimately, improved patient functional outcomes and quality of life.