Estimation of prostate cancer volume by endorectal coil magnetic resonance imaging vs. pathologic volume

Objective: Since tumor volume is recognized as an important predictor of clinical stage and disease outcome of prostate cancer, accurate preoperative estimation of tumor volume can play an important role in planning the appropriate treatment and establishing a patient's prognosis. We performed this study to evaluate the accuracy of the endorectal coil magnetic resonance (MR) technique for reliable prediction of tumor volume in patients with prostatic cancer. Material and Methods: Endorectal coil MR imaging was performed in 57 consecutive men who were suspected to have prostate cancer. Subsequent ultrasound-guided transrectal biopsy revealed prostate cancer in 44 cases. The pathological volume of the surgical specimens of 25 selected patients who underwent radical prostatectomy was retrospectively compared to the volume estimated by endorectal coil MR studies, and the Pearson correlation coefficient was calculated. Results: In 15 patients the estimated size of the tumor was within 15% of the true tumor volume; in the remaining 10 cases MR imaging tended to underestimate large tumors and overestimate small ones. A significant correlation between the volumes as determined with MR imaging and measurements of surgical specimens was observed (r 0.94; slope 0.82). To our knowledge, this is the best correlation found between pathological volume and tumor volume as evaluated by any other imaging modality. Conclusions: Endorectal coil MR imaging is a powerful means of evaluating the prostate gland; however, further improvements in imaging and/or volume calculation are required to provide a more accurate preoperative assessment of prostate cancer volume.