Potential of (1)H MR spectroscopic imaging to segregate patients who are likely to show malignancy of the peripheral zone of the prostate on biopsy

Purpose: To evaluate the potential of MR spectroscopic imaging (MRSI) to segregate patients who, upon prostate biopsy, are more likely to show a malignancy in the peripheral zone (PZ) of the prostate gland.

Materials and methods: Before biopsy, MRSI was carried in 123 men with elevated prostate specific antigen level or an abnormal digital rectal examination. After the MRSI investigation, all patients underwent systematic transrectal ultrasound guided biopsy and were categorized using standard random number tables into the following two groups: (i) Group I, a 62 member training set; and (ii) Group II, a 61-member test set. The cutoff value for the [citrate/(choline+creatine)] ratio for patients in the training set was obtained using the receiver operating characteristic (ROC) curve method. This value was then applied to the test set of patients as well.

Results: The ROC method gave a cutoff value of 1.2 for the [Citrate/(Choline+Creatine)] ratio. When applied as a malignancy-predictor to the test group of patients (Group II), the ROC method generated the following results: sensitivity, 77%; specificity, 83%; negative predictive value, 93%; positive predictive value, 55% and accuracy, 82%.

Conclusion: The results indicate that patients who are deemed as malignancy-positive in the PZ by MRSI using the ROC cutoff may be subjected to prostate biopsy to confirm the diagnosis of cancer.