MRI Offers Better Prediction of Extracapsular Extension Based on Tumor Contact Length
By: Dan Sperling, MD
At the time of radical prostatectomy (surgical removal of the prostate gland) the presence of extracapsular extension (ECE) is associated with a higher rate of treatment failure. ECE means that tumor cells are seen growing in the tissue surrounding the prostate. Until recently, various efforts to predict ECE included the following:
- Probability based on a combination of PSA, Gleason score, and clinical stage
- An irregular bulge in the capsule as seen on ultrasound or detected during the digital rectal exam (DRE)
- Assymetrical neurovascular bundles
- Breech of the capsule with evidence of direct tumor extension
- Broad tumor contact length with the capsule
A new study evaluated the ability of MRI to evaluate the tumor contact length (TCL), defined as the amount of prostate cancer in contact with the prostatic capsule. The purpose was to explore the ability of MRI-determined TCL to predict microscopic ECE when compared with other predictors.[i]
The research involved 111 consecutive patients who had proven prostate cancer detected by image-guided targeted biopsy. All patients had radical prostatectomy, and the specimens were subjected to pathological (laboratory) analysis. 71 patients (64%) had tumor confined to the prostate, while 40 patients (36%) were determined to have tumor extending beyond the prostate. For each specimen showing microscopic ECE, the reporter correlated it with cancer volume, Gleason score, and TCL. In addition, two other factors were assessed:
- The correlation between the microscopic ECE and the TCL identified on MRI
- The ability of other pre-operative variables (cancer core involvement on targeted biopsy; Partin tables) in predicting microscopic ECE.
The investigators found that with a threshold of MRI-TCL of 20mm, “the accuracy to diagnose microscopic-ECE was superior to accuracy of conventional MRI-criteria…” They concluded, “MRI-determined tumor contact length could be the promising quantitative predictor of microscopic ECE.”
The importance of this research lies in its implications for treatment planning. The probability of ECE can aid the clinician and the patient in choosing how aggressively to plan the therapy. The use of advanced multiparametric MRI performed on a powerful 3T magnet prior to biopsy plays an important role in detecting the presence of a tumor, its location, and evaluating its contact length with the capsule if appropriate.
[i] Baco E, Rud E, Vlatkovic L, Svindland A et al. Predictive value of magnetic resonance imaging determined tumor contact length for extra-capsular extension of prostate cancer. J Urol. 2014 Aug 20. Doi: 10.1016/7.juro.2014.08.084. [Epub ahead of print]
