Prognostic Significance of Visible Lesions on Transrectal Ultrasound in Impalpable Prostate Cancers: Implications for Staging

Abstract

Purpose: The current tumor-node metastasis (TNM) staging system classifies impalpable prostate cancers identified by needle biopsy and invisible by imaging as T1c and those visible as T2. Palpable cancers are classified as at least T2. However, most urologists consider impalpable prostate cancers T1c tumors, irrespective of findings on transrectal ultrasound (TRUS). The aim of this article is to provide a differentiated view of the significance of TRUS findings for staging purposes in impalpable prostate cancers. Patients and Methods: A consecutive series of 1,670 patients with impalpable tumors and palpable T2 cancers after radical prostatectomy were evaluated. Tumor characteristics and 5-year biochemical cure rates of cancers invisible and visible on TRUS were compared, as well as the rates of impalpable but visible and palpable T2 cancers. Results: Impalpable cancers invisible on TRUS presented significantly more favorable pathologic stages and lower cancer volumes than those visible on TRUS (P = .002, P = .010). In the latter, these clinical features were more favorable compared with T2 cancers (P < .001, P < .001). Progression-free probability of impalpable cancers invisible on TRUS was 86.8%; progression-free probability for impalpable cancers visible on TRUS was 85.4% (log-rank test P = .2060). The corresponding rate for T2 tumors was 73.9%, significantly lower when compared to those of visible and impalpable cancers (log-rank test P = .0001). Conclusion: Impalpable prostate cancers invisible on TRUS present more favorable cancer features than those that are visible on TRUS. However, these differences are not as pronounced as those between impalpable but visible cancers and palpable T2 tumors. Thus, based on our data, it seems inappropriate to classify impalpable prostate cancers visible on TRUS as T2 cancers.