Do impalpable stage T1c prostate cancers visible on ultrasound differ from those not visible?

We assessed whether the appearance of cancer within the prostate on sonography is associated with different pathological features and/or prognoses compared with nonvisible impalpable cancers defined as stage T1c by the TNM staging system.

We analyzed the clinical and pathological features, and progression rate in 323 patients with clinical stage T1cNX M0 cancer treated with radical prostatectomy between 1983 and 1998. Mean followup was 46.8 months (range 1 to 186).

Of 323 impalpable stage T1c cancers 170 (53%) were visible and the remainder was not visible on ultrasound. There were no significant differences in clinical or pathological features of the cancers in these 2 groups. The prostate specific antigen nonprogression rate at 5 years was also similar for patients with impalpable cancer regardless of whether the lesion was or was not revealed by ultrasound (mean +/- SE 87% +/- 6% and 91% +/- 6%, respectively, p = 0.3767). Of the 170 visible cancers 55 patients had a hypoechoic lesion considered highly suspicious for cancer. These cancers were higher grade, more extensive, less likely to be confined to the prostate and the prognosis was significantly worse than that of impalpable cancer whether or not they were visible at a less suspicious level (IV or less, p = 0.011). However, such highly suspicious visible cancers are rarely visualized today. Initial serum prostate specific antigen more accurately predicts the pathological stage of impalpable cancer than transrectal ultrasound results.

Impalpable cancers currently detected have similar pathological features and prognoses whether or not they are visible by ultrasound. Therefore, it is reasonable to categorize impalpable cancers as stage T1c and analyze the response to treatment regardless of the results of ultrasound.