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The MRI-based targeting concept
The surge of mpMRI in the field of prostate cancer diagnosis and treatments has changed the paradigm. Making the invisible visible allows the doctors to instore principles of a conservative treatments with less side effects than radical treatments. The philosophy behind focal therapy is to preserve as much as possible any « noble » structure involved in a particular function such as erection, ejaculation, continence and micturition. To reach that goal the most innovative technologies are used. The ability to visualize the lesions are transferred to the ultrasound scan (USS) equipment by a fusion software mpMRI toward USS allowing to perform targeted biopsies (TB) with an accuracy never reached before (picture 32). The analysis of these high-resolution biopsy cores gives a very accurate level of information regarding the nature of the cancer.
Picture 32 : High resolution targeted biopsy procedure based on a MRI/US fusion system
The diagnostic importance of targeting accurately the lesions
More than simply showing the suspicious areas where the probability of reaching the cancer is far higher than in the remaining normal prostate the content itself of each TB bears optimized quality information. Not only the number of positive biopsies because targeted is increased but also a higher percentage of cancer invasion on each biopsy core and far more crucial the degree of aggressivity (ISUP) retrieved in a targeted biopsy set is more accurate than in random biopsies (RB) [23]. Due to the prostate cancer mpMRI data transferred to the USS by the fusion software in real-time prostate biopsies as the cornerstone of the prostate cancer treatment decision making has reached an unprecedented level of accuracy. Indeed studies have shown that the surge of TB has increased the cancer detection rates to 80-85 % in some expert centers compared to 25-30% when RB only [24]. In addition TB have also reduced drastically the dangerous understimation of the aggressivity of the disease with its potentially heavy consequences.
Picture 56 : Prostate biopsy mapping record
From diagnosis to focal therapy
The fusion software which is now included in the ultrasound scan machine or complementary equipment by most of the suppliers has the fundamental function of recording every step of the targeted biopsy procedure. This information is of tremendous importance to move from the diagnostic to the therapeutic field. Indeed the trajectory of every biopsy is recorded in the patient file (picture 56) and each positive biopsy is labelled in a way to localize very accurately the part(s) of the prostate where the cancer lies. Most of the focal therapies in prostate cancer are performed by introducing through the perineum needles which deliver a certain kind of energy. By using the localization data recorded for a given patient during the biopsies the software can easily propose a treatment planning with the number of needles and their location in order to cover completely the cancerous lesion(s) (video 7). In the illustration proposed each fiber is represented by a yellow cylinder which symbolizes the 1 cm diameter light emitted by each laser fiber. In the present case the treatment planning proposed by the software was a left hemiablation.
Video 7 : MRI/US fusion is the missing link
