Interval carcinomas in the European Randomized Study of Screening for Prostate Cancer (ERSPC)-Rotterdam.

BACKGROUND: The interval cancer rate is an important parameter for determining the sensitivity of a screening procedure and the screening interval. We evaluated the time and mechanism of detection and the stage distribution of interval prostate cancers diagnosed during a 4-year screening interval.

METHODS: We determined the rate of interval cancers and the sensitivity of the screening protocol (involving prostate-specific antigen, digital rectal and transrectal ultrasound examinations) in a cohort of 17 226 men (8350 on the screened arm, 8876 on the control arm) enrolled consecutively on the European Randomized Study of Screening for Prostate Cancer-Rotterdam. Men on the screened arm received a first screen between October 1993 and December 1996 and a scheduled second screen 4 years later. Prostate cancers detected in men enrolled on the control arm over the same 4-year period and, between screens, in men on the screened arm, were identified by linkage to the Dutch national cancer registry.

RESULTS: During the first screen, 412 prostate cancers were detected. During the subsequent 4-year period, 135 cancers were diagnosed in men in the control arm and 25 cancers were diagnosed in men in the screened arm. Seven of the 25 cancers were diagnosed in men who had refused a recommended biopsy at their initial screen. Of the remaining 18 cancers, all were classified as stage T1A-C or T2A and none were poorly differentiated or metastatic. The rate of interval cancers relative to the number of cancers in the control group was 18.5% (25/135), or 13.3% (18/135), if the seven who refused an initial biopsy were excluded. The sensitivity of the screening protocol was 79.8% when considering all 25 interval cancers and 85.5% when considering 18 interval cancers.

CONCLUSION: The interval cancer rate with a 4-year screening interval was low, confirming that the screening procedure has a high sensitivity and that the 4-year screening interval is reasonable.