The manuscript by Crawford and Barqawi reviews an important concept in prostate cancer diagnosis and treatment. As we learn that the expected number of men diagnosed with prostate cancer will likely double by the year 2015 (to over 400,000 new cases per year), it is certainly time to address new approaches to its treatment.
The concept of focal therapy is a significant departure from the current, long-held belief that total-gland therapy is the only option for the treatment and cure of prostate cancer. The authors draw parallels with the development of breast cancer treatments, and it is certainly in keeping with the major movement in all surgery toward minimally invasive and more focal excisions. If there is one theme in surgical oncology today, it is that of maximizing therapy to the tumor and its borders and minimizing any damage to the surrounding tissues. This strategy is supported by the rapid introduction of robots, laparoscopes, and, most importantly, by the integration of imaging and visualization tools into the procedure room. This is the principle behind the ever-growing movement of image-guided therapy.
The authors introduce the approaches being taken to perform mapping biopsies to guide focal therapy. This work is still in the early stages of development. While the authors acknowledge the need and potential for imaging in the treatment of prostate cancer, they do not provide enough credit to existing image-guided approaches. For example, imaging with ultrasound is widely used to guide biopsies and implantation of radiation sources in brachytherapy. Similarly, in some centers, magnetic resonance imaging (MRI) has been used to guide brachytherapy and prostate biopsies, with excellent success.
There are also many investigators working with both ultrasound and MRI to guide focused ultrasound thermal ablation. In several trials in Europe and the United States, transrectal ultrasound (TRUS)-guided high-intensity focused ultrasound (HIFU) is in clinical trials, initially as a global therapy, but perhaps in the future as a focal therapy, akin to a "prostate lumpectomy." As shown in uterine fibroids and breast cancer, MR-guided focused ultrasound surgery (MRgFUS) allows for real-time highly accurate thermometry during the procedure. This provides a unique monitoring and guidance method, unavailable in other thermal ablative procedures.
Noninvasive Techniques Needed
The authors discuss in detail the three-dimensional mapping biopsies that are being performed at one or two institutions. However, they fail to mention that these require a large number of cores to be removed (as many as 80 at a time), and this is after the patient has already had a diagnostic biopsy. This seems to be an overly invasive way to determine the extent of cancer, underscoring the point that a noninvasive imaging method to identify focal tumors is desperately needed. This challenge to imaging research is actively under investigation at many institutions. New MRI techniques using higher field strength magnets (3T) and a multiparametric approach combining all MR data (such as dynamic contrast enhancement, spectroscopy, T2 mapping, diffusion imaging, and now even C13-hyperpolarization methods) appear to offer the most comprehensive approach.
This overview is indeed timely; it introduces a new concept and approach that still needs to be truly tested before its clinical value is known. Although this technique undoubtedly represents a beginning, it offers promise in managing a very significant problem facing our patients, their families, and the health-care community today.
Clare Tempany, MD