Detection of Prostate Cancer: Serendipity Strikes Again

Source: McNaughton-Collins M, Ransohoff DF and Barry MJ
Journal of theAmerican Medical Association Nov 12, 1997; Vol 278 (No 18): pp 1516 - 9

The definition of serendipity is to happen upon something bychance. A cancer may be "picked up" by chance, if the screening testis falsely positive because of a reason other than the malignancy.Some contend that not infrequently colorectal cancer may be detectedthis way with occult fecal blood screening programs. The occult bloodcould be due to colitis, benign adenoma, hemorrhoids, etc. Themainstay of screening for prostatecancer has been digital rectal examination (DRE) and prostatespecific antigen (PSA). With these things in mind, the authors ofthis article sought to prove that a substantial number of cases ofprostate cancer were detected by chance when utilizing the screeningmethods of DRE and PSA. The data reported were not compiled into aformal meta-analysis but utilized a compilation of historical datafrom past studies.

Serendipity is evident when DRE abnormality leads to a biopsy thatyields cancer but not in the area of the palpable abnormality. Of 175biopsy proven prostate cancers, 28% were in areas that were notwithin the palpable abnormalities. The palpable abnormalities aremostly benign prostatic hypertrophy (BPH) and prostatitis.

Serendipity is also evident when PSA is elevated, leading to abiopsy that yields cancer but in a tumor too small to be completelyaccountable for the elevation in PSA. It has been reported in autopsyseries that a tumor volumes of 0.5 cm3 to 1.0 cm3, were associatedwith PSA in the normal range (£ 4 ng/mL) in over 90% of thetime. In the 594 patients reviewed from multiple past reports, 26%(152 patients) had tumors less than 1.0 cm3, a size "too small" tohave an elevated PSA. Those 152 patients got biopsy and were found tohave cancer serendipitously.

The clinical implications of this discovery is unclear.Serendipity detected prostate cancer tends to propose that DRE andPSA screening's true utility is overestimated. How doesserendipitously discovered prostate cancer affect overall outcome inthese patients? Some contend that until we can truly determine thenatural history of this disease, we will never be able to fullyanswer that question. If finding smaller cancers is really important,then serendipity in prostate cancer screening is important since itfinds cancer sooner. How is this going to affect future screeningpractices? Most likely, it will affect no change, but just create anawareness of the fact that medicine is not a perfect science - luckhelps out sometimes in the case of screen for colon cancer andprostate cancer.