Understanding the relationship between tumor size, gland size, and disease aggressiveness in men with prostate cancer

Objective: To determine the relationship between prostate gland and tumor volume in men undergoing radical prostatectomy (RP) for prostate cancer. We hypothesized that larger tumors within smaller prostate glands are associated with more aggressive disease characteristics.

Methods: Records of patients undergoing RP from 2000-2008 at a single institution were reviewed retrospectively. The dominant nodule was considered to be the largest focus of cancer within the prostate, and the dominant nodule-to-prostate volume ratio (DNVR) was calculated according to the ratio of the dominant nodule volume to the gland weight. Cox regression was performed to assess the relationship between DNVR and both pathologic outcomes (Cancer of the Prostate Risk Assessment post-Surgical score) and biochemical recurrence (BCR).

Results: At a median follow-up of 3.7 years, 174 patients (7.2%) suffered BCR. There was no linear correlation between tumor volume and gland size (R = -0.09). DNVR above the median (≥0.033 cc/gm) was closely associated with high clinicopathologic risk as measured by Cancer of the Prostate Risk Assessment post-Surgical score (hazard ratio, 35.53; 95% confidence interval, 14.42-87.55 for high- vs low-risk groups). In the univariable analysis, both tumor diameter and DNVR were associated with increased risk of BCR. However, in the multivariable model, only tumor diameter remained a significant predictor of BCR (hazard ratio, 2.02; 95% confidence interval, 1.04-3.91).

Conclusion: Increased DNVR appears to be a characteristic of aggressive prostate tumors, although it did not predict BCR in the present study. However, these data support the association between tumor diameter and BCR after RP for prostate cancer independent of other key clinicopathologic features.