Hormonal ablation of prostatic cancer: effects on prostate morphology, tumor detection, and staging by endorectal coil MR imaging.

OBJECTIVE

The purpose of our study was to evaluate the effect of androgen deprivation therapy on the MR imaging findings of prostate gland anatomy and cancer pathology in men with prostatic cancer treated with hormonal ablation before radical prostatectomy.

MATERIALS AND METHODS

Twenty-two patients (mean age, 66 years old) were divided into two groups: in group I (n=10), MR imaging studies were done before and after hormonal treatment; in group II (n=12), MR imaging studies were done only after hormonal treatment. MR imaging was performed on a 1.5 T-scanner (Signa; General Electric Medical Systems, Milwaukee, WI) and included transverse plane phased-array coil T1-weighted images (TR/TE, 600/12), combined endorectal phased-array coil transverse plane T1-weighted images, fast spin-echo T2-weighted (4000/102), and coronal plane fast spin-echo T2-weighted images. Image evaluation was by consensus and included assessment of the gland size, signal intensity, tumor depiction, extracapsular extension, seminal vesicle invasion, and overall staging accuracy (Jewett and Whitmore classification). MR imaging findings were correlated with pathologic findings of step section radical prostatectomy.

RESULTS

After hormonal therapy, the volume of the prostate gland showed a mean decrease of 33.5% +/- 19.6% SD (range, 0-64%). Volume reduction in the transition zone (mean 29.2% +/- 22% SD) was less than in the peripheral zone (mean, 55.8% +/- 25.8% SD) (p < .05). On T2-weighted images, the peripheral zone showed homogeneous decreases in signal intensity in 13 of 22 (58%) patients. Compared with pathologic findings, the accuracy of tumor detection by MR imaging was 74% (98 of 132 sites). Tumor presence was overestimated in 32 of 132 (24%) sites. Overall staging accuracy after hormonal ablation was 68% (15 of 22). The positive predictive value and negative predictive value for extracapsular extension were 57% (13 of 23 sites) and 90% (19 of 21 sites), respectively, and for seminal vesicle invasion were 80% (8 of 10 sites) and 97% (33 of 34 sites), respectively.

CONCLUSION

As detected by MR imaging, hormonal ablation caused a decrease in size and signal intensity of the prostate gland and seminal vesicles and overestimation of tumor presence and extracapsular extension.