MRI Imaging of Prostate Cancer: Functional Parameters in Combination
Systematic scientific evaluation of various prostate imaging techniques helps determine which are best suited for a given clinical purpose. Just over a year ago, a study from Memorial Sloan-Kettering’s radiology department investigated which combination of MRI functional parameters was most advantageous for detecting prostate cancer recurrence after primary radiation therapy.[i]
The authors’ intent was to compare which of the following parameters offered the greatest diagnostic accuracy:
- T2 weighted imaging alone
- T2 weighted + Diffusion Weighted Imaging (DWI)
- T2 weighted + Dynamic Contrast Enhancement (DCE)
- T2 weighted + DWI + DCE
The study involved 53 patients who previously had radiation therapy and were suspected of recurrence. Each patient underwent a biopsy within six months prior to MRI (ample time for the healing and absorption of any post-biopsy blood artifact in the gland that could compromise the accuracy of cancer detection). All imaging was T2 weighted, and included DWI and DCE sequences.
Two readers, independent of each other, evaluated all four types of images listed above for each patient, using a 5-point scale for determining the likelihood of cancer (0 = definitely no cancer, 5 = definitely cancer). The readers were blinded to the biopsy results. Their evaluations were compared with each other’s, and with biopsy findings.
At the time of biopsy, 35 men (66%) were found to have recurrent cancer. The authors found that multiparametric MRI (T2 weighted with DWI) was more accurate than T2 weighted alone. They did not, however, feel that the addition of DCE improved detection (either T2 weighted + DCE, or T2 weighted + DWI + DCE). Furthermore, there was greater agreement between the two readers over T2 weighted + DWI than simply T2 weighted alone.
This study, though small, points to the significant advantage of combining more than one parameter when using prostate MRI to identify regions of interest. It is particularly valuable to detect recurrence early, because if it is still localized, the patient may be qualified for a potentially curable salvage treatment. Even if the cancer has penetrated the capsule, imaging can rule regional metastasis in or out, facilitating the development of a treatment plan that may include adjuvant (supportive) hormone therapy for managing control of the cancer.
[i] Donati OF, Jung SI, Vargas HA, Gultekin DH et al. Multiparametric prostate MR imaging with T2-weighted, diffusion-weighted, and dynamic contrast-enhanced sequences: are all pulse sequences necessary to detect locally recurrent prostate cancer after radiation therapy? Radiology. 2013 Aug;268(2):440-50.