Role of Endorectal Prostate MRI in Patients with Initial Suspicion of Prostate Cancer

Abstract

Purpose: To evaluate the role of conventional endorectal prostate MRI in patients with initial suspicion of prostate cancer.

Materials and Methods: Ethics board approval was received for this retrospective study of 87 men who underwent 1.5-Tesla conventional prostate MRI with a combination of endorectal and body phased-array coils for suspected prostate cancer before their first systematic 12-core TRUS-guided biopsy. Three radiologists independently analyzed the images, dividing the prostate into 12 regions corresponding to the biopsy scheme and scoring each region for the presence of prostate cancer on a 5-point scale. Results were analyzed by prostate region. ROC analysis was done and descriptive statistics were calculated. The negative predictive value, specificity, sensitivity and positive predictive value were calculated using dichotomized scores (benign tissue = scores of 1 and 2; malignant tissues = scores of 3, 4, and 5).

Results: Biopsy revealed cancer in 47/87 patients (26 low-grade [Gleason score 6]; 21 high-grade [Gleason score ≥ 3 + 4]), and 184/1044 cores (77 low-grade and 107 high-grade) with a median of 3 positive cores per cancer patient (range 1 – 12). The areas under ROC curves were 0.65 – 0.67 for cancer detection by region overall and 0.75 – 0.76 for the detection of high-grade cancer by region. Statistic figures for the detection of all cancers/high-grade cancers by region were as follows: negative predictive value, 87.4 – 88.2 %/92.6 – 93.1 %; specificity, 72.3 – 79.4 %/71.5 – 79.8 %; sensitivity, 49.5 – 54.8 %/62.6 – 69.2 %; and positive predictive value, 29.3 – 34.0 %/29.4 – 34.7 %.

Conclusion: In patients with suspected prostate cancer, negative MRI findings indicate the absence of high-grade prostate cancer on subsequent TRUS-guided 12-core biopsy with high probability. However, agreement between conventional 1.5-T endorectal prostate MRI and systematic 12-core TRUS-guided biopsy for the detection of prostate cancer appears to be moderate.

Citation Format:

• Franiel T, Vargas AH, Mazaheri Y et al. Role of Endorectal Prostate MRI in Patients with Initial Suspicion of Prostate Cancer. Fortschr Röntgenstr 2013; 185: 967-974

Zusammenfassung

Ziel: Diese retrospektive Studie untersucht die Wertigkeit der MRT der Prostata mit Endorektalspule bei Patienten mit initialem Verdacht auf ein Prostatakarzinom.

Material und Methoden: Ein positives Votum der lokalen Ethikkommission lag vor. 87 Patienten mit initialem Verdacht auf ein Prostatakarzinom wurden im 1,5 Tesla MRT mit der kombinierten Endorektal-Body phased array Spule untersucht. Anschließend erfolgte eine systematische TRUS-gestützte 12fach-Biopsie. Jede Prostata wurde entsprechend dem Schema der Stanzbiopsie in 12 Areale unterteilt. Mit den T1w- und T2w-MRT-Aufnahmen wurde für jedes Areal von 3 unabhängigen Radiologen standardisiert und auf einer 5-Punkte-Skala die Wahrscheinlichkeit für ein Prostatakarzinom angegeben. Eine ROC-Analyse und eine deskriptive Statistik wurde durchgeführt. Negativ prädiktiver Wert, Sensitivität, Spezifität und positiv-prädiktiver Wert wurden nach Dichotomisierung des Scores (benigne = Score 1 und 2, maligne = Score 3, 4, 5) berechnet.

Ergebnisse: 47/87 Patienten (26 low-grade, 21 high-grade) mit 184/1044 Stanzbiopsien (77 low-grade, 107 high-grade) waren positiv für ein Prostatakarzinom. Ein Karzinompatient hatte im Median 3 positive Stanzbiopsien (Spannweite 1 – 12). Die Area under ROC curve für die Detektion des Prostatakarzinoms betrug zwischen 0,65 – 0,67 und bei ausschließlicher Berücksichtigung der high-grade-Prostatakarzinome zwischen 0,75 – 0,76. Für die Detektion der Prostatakarzinome/high-grade-Prostatakarzinome ergab sich ein negativ-prädiktiver Wert von 87,4 % – 88,2 %/92,6 % – 93,1 %, eine Spezifität von 72,3 – 79,4 %/71,5 – 79,8 %, eine Sensitivität 49,5 – 54,8 %/62,6 – 69,2 % und ein positiv-prädiktiver Wert von 29,3 – 34,0 %/29,4 – 34,7 %.

Schlussfolgerung: Bei Patienten mit initialem Verdacht auf ein Prostatakarzinom kann ein negatives MRT mit sehr hoher Wahrscheinlichkeit das Vorliegen eines high-grade-Prostatakarzinoms in der nachfolgenden TRUS-gestützten Stanzbiopsie ausschließen. Insgesamt stimmen jedoch die Ergebnisse der konventionellen 1,5 Tesla MRT mit Endorektalspule mit den Ergebnissen der systematischen TRUS gestützten Biopsie nur moderat überein.

Key words

prostate cancer - initial suspicion - MRI

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