Our study was conducted retrospectively in a population of 507 patients of whom we selected 220 – a substantial number - who had a preoperative MRI. For the first time, our paper showed that the accuracy of MRI in locating prostate cancer might be influenced by prostate weight.
Our results showed a better correlation between MRI scan and radical prostatectomy specimen analysis with higher sensitivity of MRI at tumour localisation compared to TRUS biopsy. We have also shown the improved accuracy of MRI for basal tumours compared to apical tumours, with better localisation in larger prostates (≥50g). Our study clearly showed that in comparison to the TRUS-biopsy, MRI was very effective in the localization of tumours of the base, mid-gland and TZ, especially if large prostates (>50g). Using only TRUS-biopsy in pre-therapeutic assessment of prostate cancer is not enough. MRI allows for a more systematic and complete evaluation of patients before therapeutic decisions are made.
Our results confirmed the previous study by Mullerad, et al. in tumour localization compared TRUS-biopsy versus MRI. Because guidelines on TRUS-biopsy have been modified during this last decade, 50% of our patients had at least 10 biopsies. A prospective study to prevent bias related to number of biopsy cores would probably take too long to obtain a similar volume of data. By increasing the number of cores, the TRUS biopsy had a good accuracy on tumour location particularly for apical prostate cancer, confirming the findings from the study by Introini, et al. At least 10 cores were obtained in 50% of our patients and over 1,720 prostate regions were analysed. To reduce the impact of any bias from different core numbers (6, 10 or 16), we conducted a subgroup analysis according to core number. The sensitivity of prostate biopsy at tumour localisation improved with increase in the number of biopsies from sextant to10, however, this did not improve further when 16 biopsies were undertaken. In the sextant biopsy, 33.14% of prostate biopsies correlated with the RP specimen compared to 44.7% when 10 biopsies were taken (p = 0.003). The sensitivity of 16-core biopsies was lower at 39% (p = 0.0188). The MRI scan had a higher localization capability compared to biopsies irrespective of number of cores.
Although the radiologists who analysed the MRI images were aware of whether the patients had positive or negative biopsies, they did not know the exact location of the malignancy. Moreover, they could not know the results when MRI was performed pre-biopsy. The radiologists were informed of the results (positive or negative) of the TRUS-guided biopsies, except for patients whose MRIs were pre-biopsy but were not informed of the exact location of tumours.
A significant number of patients had no radiologically detectable tumour despite having a positive biopsy - thus highlighting the objectivity of the radiologists who interpreted the review. The surgical specimens were used as a reference. In fact, malignancy was detected in 1381/1760 regions (78.46%) on RP specimens, 743/1760 regions (42.21%) on MRI, and only 575/1760 (32.67%) regions on TRUS-guided biopsy.
In conclusion, MRI is superior to TRUS biopsy in tumour localization of prostate cancer except at the apex. Prostate MRI is more accurate in larger prostates (≥50g). Increasing the number of biopsies from standard sextant to 10 improves the localization of prostate cancer by TRUS-biopsy despite the superiority of MRI. With increasing utilisation of technological advances in MRI scanning, especially 3 Tesla MRI, dynamic contrast-enhanced MRI and MR diffusion imaging the sensitivity of MRI scan in tumour localization is bound to improve, enhancing our capabilities in directing focal treatments for localized prostate cancer. We recommend a minimum of 10 cores before focal therapy for localized prostate cancer.
- Goris Gbenou MC, Peltier A, Addla SK, Lemort M, Bollens R, Larsimont D, Roumeguère T, Schulman CC, van Velthoven R. Localising Prostate Cancer: Comparison of Endorectal Magnetic Resonance (MR) Imaging and 3D-MR Spectroscopic Imaging with Transrectal Ultrasound-Guided Biopsy. Urol Int. 2011 Oct 15.
- Mullerad M, Hricak H, Kuroiwa K, Pucar D,Chen HN, Kattan MW, et al.: Comparison of endorectal magnetic resonance imaging, guided prostate biopsy, and digital rectal examination in the preoperative anatomical localisation of prostate cancer. J Urol 2005;174:2158-63(14).
- Introini C, Naselli A, Vigliercio G, Spina B, Truini M, Puppo P: Can biopsy be reliable predictor of spatial distribution of prostate cancer? Comparison of a novel biopsy regimen with radical prostatectomy findings. Urology 2006; 68: 1301–1304.
Maximilien C. Goris Gbenou, MD* as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.