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The Clinical Value of DWI and T2WI MRI in the Detection of Transitional Zone Prostatic Cancer

Al-Yasi ZI, Kadhim MA and Jawad MK

Background: The prostate cancer is one of the commonest non-cutaneous cancers detected among elderly men. The difficulty in interpretation of the transitional zone prostate MRI arises mainly from the presence of benign prostatic hyperplasia (BPH) nodules in the transitional zone.

Objective: The objective of this study is to evaluate the clinical efficacy of DWI in combination with T2WI for the detection of transitional zone prostate cancer, compared with T2WI alone.

Patients and methods: A total of 58 patients with clinical suspicion of prostatic cancer were evaluated by 1.5 T MRI. Two diagnostic protocols were designed, protocol A consists of only data obtained from T2WI, protocol B consists of T2WI and DWI. The likelihood of the presence of prostate cancer in transitional and central zone was assigned using a 5 point scale after evaluating the entire prostate in each reading session, scales of 5, 4, and 3 were considered positive results and scales 1 and 2 were considered negative results.

Results: Transitional zone prostate cancer was identified histopathologically in 23/58 patients. MRI diagnostic performance: In protocol A, the sensitivity is 56.5%, specificity is 62.9% and accuracy is 60.3%. Positive predictive value PPV is 50% while negative predictive value NPV is 68.8%. In protocol B, the sensitivity is 91.3%, specificity is 80% and accuracy is 84.5%. Positive predictive value is 75% while negative predictive value is 93.3%. Diagnostic protocol B has a significantly better sensitivity and specificity than protocol A (p˂0.05). According to ROC curve analysis, the cut point of protocol A scale is 2, so protocol A scale (≥ 2) is predictive for the diagnosis of malignant lesions (AUC=67.5%). The cut point of protocol B scale is 4, so protocol B scale (≥ 4) is predictive for the diagnosis of malignant lesions (AUC=87.3%). The cut off ADC value is 0.99 × 10-3 mm²/sec, so ADC value (<0.99 × 10-3mm²/ sec) is predictive for the diagnosis of malignant lesions with 91.3% sensitivity, 76% specificity, and 83.3% accuracy.

Conclusion: Combination of DWI (ultra-high b value) with T2WI significantly increases the diagnostic accuracy of transitional zone prostatic cancer and scale ≥ 4 is associated with high proportion of malignancy.