EARLY DETECTION OF PROSTATE-CANCER - SERENDIPITY STRIKES AGAIN

An underappreciated characteristic of prostate cancer screening is tha t it may detect some prostate cancers solely by serendipity or chance, Serendipity, previously described in the detection of colonic neoplas ms, could affect prostate cancer detection when a screening test resul t is abnormal for reasons other than the presence of prostate cancer, but prostate cancer is coincidentally detected during the subsequent e valuation of the abnormal screening result. We reviewed published arti cles about prostate cancer screening, searching for evidence of serend ipity. We defined serendipity in digital rectal examination (DRE) scre ening as the discovery of a prostate cancer by the random biopsy of an area of the prostate gland other than the palpable suspicious area th at prompted the biopsy. We defined serendipity in prostate-specific an tigen (PSA) screening as the discovery of a prostate cancer by the ran dom biopsy of a nonpalpable (stage T1c) prostate cancer less than 1.0 cm(3) in volume, since tumors less than 1.0 cm(3) are generally too sm all to cause elevated PSA levels. We found that serendipity may be res ponsible for the detection of more than one quarter of apparently DRE- detected prostate cancers and up to one quarter of apparently PSA-dete cted cancers. Additionally, serendipity played a larger role in the de tection of smaller tumors that are common but of uncertain clinical si gnificance. We conclude that serendipity-detected prostate cancers con tribute to an overestimation of the true information value of DRE and PSA screening. Whether serendipity is advantageous in prostate cancer screening depends on the as yet uncertain outcomes for men with smalle r prostate cancers. However, given our estimates of the potential magn itude of the impact of serendipity, the currently popular DRE- and PSA -based screening strategy may not be optimal. If smaller prostate canc ers are important, then we are not finding enough; if they are unimpor tant, then we are finding too many that we may feel compelled to treat aggressively.