'Vanishing' prostate cancer in radical prostatectomy specimens: incidence and long-term follow-up in 38 cases.

OBJECTIVE: To determine the incidence and long-term follow-up of the 'vanishing cancer' phenomenon, as complete sampling of some radical prostatectomy (RP) specimens reveals no residual cancer.
MATERIALS AND METHODS: The Mayo Clinic prostate cancer RP database for 1966-1995 was searched for all cases in which there was no residual adenocarcinoma (pathological stage pT0). Each case was confirmed by a review of all tissue specimen slides. Various clinical and pathological features were evaluated, and the follow-up obtained for all patients.
RESULTS: Among 6843 RPs there were 38 in which no residual cancer was identified despite careful sampling. There was a 10-fold decline in the incidence of this finding, from 2.1% before 1980 to 0.2% in 1993-95; this decline appeared to be caused by a decrease in the frequency of diagnosis of cancer by transurethral resection from > 10% before 1990 to < 2% in 1993-95. The mean (range) age of the patients was 63 (38-75) years. All cancers on biopsy or transurethral resection were well or moderately differentiated; clinical stages included T1a (42% of cases), T1b (45%) and T2 (13%). Six patients had a nerve-sparing RP, all after 1990. The mean follow-up was 9.6 (1.0-28.5) years, and there were no recurrences of cancer; the serum prostate specific antigen concentration remained at < 0.2 ng/mL in surviving patients. Six patients (16%) died from intercurrent disease.
CONCLUSIONS: The incidence of 'vanishing cancer' declined between 1966 and 1995, probably as a result of the decline in the use of transurethral resection, occurring in 0.2% of RPs. The prognosis in such patients is excellent, indicating that there is no apparent clinical significance to microscopic foci of cancer that remain undetected after reasonably complete pathological sampling. The inability to identify cancer in a prostate removed for biopsy-confirmed carcinoma does not indicate technical failure.