Previously, patients with suspected prostate cancer were diagnosed using a physical examination involving the palpation of the prostate (known as a digital rectal examination, DRE) and a blood sample to test their level of prostate-specific antigen (PSA). If the findings were suspicious, an ultrasound-guided prostate biopsy was performed via the rectum. This approach is viewed with increasing criticism today. These days, the primary aim is to avoid unnecessary biopsies. If a biopsy is nevertheless required, the procedure must be used to determine the precise location of the tumour in the prostate and to ensure that there are no additional tumours in the other parts of the prostate. This is also essential when planning focal therapy. This objective can be achieved by performing an mpMRI/TRUS fusion and mapping biopsy of the prostate.
Two tumours can be seen in the prostate illustrated below. An aggressive prostate tumour requiring treatment is visible in the top middle part of the figure (tumour with a dark centre), while a light-blue insignificant tumour that does not require treatment can be seen on the left-hand side of the figure.
To avoid prostate cancer being treated unnecessarily, it is important to distinguish between significant tumours that require treatment and insignificant tumours that do not require treatment. Among other factors, this distinction can be made by performing histological examinations of tissue samples from the prostate.
The standard procedure is a systematic transrectal ultrasound-guided biopsy (TRUS). This involves 10 to 12 biopsy cores being removed from the prostate via the rectum. However, this traditional method has limited sensitivity. According to autopsy studies, it stands at 53%. This means that tumours are simply overlooked during biopsies (Fig. 1). If a TRUS biopsy finds evidence of prostate cancer, the question arises as to whether the biopsy results have correctly identified the histological tumour grade. This is hugely important when planning treatment or estimating disease prognosis.
The risk of misclassifying a tumour following a traditional prostate biopsy, i.e. overlooking aggressive tumours or underestimating their aggressiveness, is between 21% and 54% (Fig. 2 and 3). Ideally, the biopsy needs to target the aggressive tumour in need of treatment so that it can be classified (Fig. 4). This is the only way of ensuring that patients are given the best possible advice.
A prostate mpMRI (multi-parametric magnetic resonance imaging) is a scan used to diagnose prostate cancer. This special MRI examination combines a standard examination with an examination involving the administration of a contrast agent and also measures the tissue density.
When using this technique, it is highly likely that an experienced radiologist will be able to locate suspected cancerous areas within the prostate. Often, these are areas that cannot be reached during traditional punch biopsies. Conversely, mpMRI can differentiate between clinically irrelevant tumours and aggressive tumours and help to avoid unnecessary intervention.
We cooperate closely in this area with the radiology department run by our premium partner, Merian Iselin Clinic in Basel (https://radiologie.merianiselin.ch/). Here, a core team of three specialists is responsible for performing and analysing the results of prostate mpMRIs. The clinic performs more than 500 examinations a year, meaning that both we as referrers and our own patients can benefit from its extensive experience and expertise in this field.
The biopsy is conducted via the perineum and not the rectum. This virtually eliminates the risk of bacterial transmission and a subsequent infection. The procedure requires a brief stay in hospital and is performed under anaesthetic.
An mpMRI/TRUS fusion and mapping biopsy of the prostate is a prerequisite for planning focal therapy. A standard transrectal biopsy of the prostate is insufficient (see study 1 below).
In the PRECISION study (2) published in the renowned New England Journal of Medicine, it was shown for the first time with extremely high scientific quality that the combination of MRI followed by a targeted fusion biopsy provides more precise results than a traditional ultrasound-guided biopsy. Just under 30% of the study participants who were given an MRI had normal results. This meant that they did not have to undergo the biopsy usually given as standard and to which the participants who did not receive an MRI were subjected.
Based on the MRI results and the targeted biopsy of the areas previously identified as suspicious, 38% were diagnosed with clinically relevant prostate cancer. In contrast, clinically relevant prostate cancer was only found in 26% of the patients who received a standard biopsy. These results show that using MRI and a fusion biopsy to assess the risks of suspected prostate cancer is much more precise than the ultrasound-guided biopsy method practised to date.
Moreover, the targeted approach reduces the diagnosis of cases of prostate cancer that generally do not require treatment by 50%. Although these cases of cancer do not put the men affected at any physical risk, being diagnosed with cancer often causes immense emotional stress.
1. van der Poel HG, van den Bergh RCN, Briers E, et al. Focal Therapy in Primary Localised Prostate Cancer: The European Association of Urology Position in 2018. Eur Urol. 2018;74(1):84-91.
2. Kasivisvanathan V, Rannikko AS, Borghi M, et al. MRI-targeted or standard biopsy for prostate-cancer diagnosis. New England Journal of Medicine. 2018;378(19):1767-77.