Recent improvements in prostate cancer outcomes may be result of shift in classification

September 06, 2005

Some of the improvement in prostate cancer survival rates over the past decade may be due to a shift in the classification of prostate tumors rather than to an actual improvement in outcomes, according to an article in the September 7 issue of the Journal of the National Cancer Institute.

Prostate cancers are assigned a score called a Gleason score that ranges from 2 to 10, based on the pathologist's estimation of the likelihood that the cancer cells will spread. Twenty years ago, doctors routinely labeled newly diagnosed prostate tumors with relatively low Gleason scores of 2 to 5, indicating a less dangerous cancer. Today, scores this low are rarely encountered, even though there has been no change in the Gleason scoring system itself in the last decade. In addition, there have been several reports of improvements in 5-year and 10-year survival in prostate cancer based on Gleason score.

To determine whether these improvements in survival are true improvements or the result of a changes in the way cancers are assigned Gleason scores, Peter C. Albertsen, M.D., of the University of Connecticut Health Center in Farmington, and colleagues collected medical records from 1,858 men diagnosed with prostate cancer between 1990 and 1992. They retrieved slides of the prostate tissue taken from these men at the time of their diagnosis, as well as the original Gleason score assignments. An experienced pathologist, blinded to the original numbers, examined the slides and assigned Gleason scores according to contemporary standards.

The study found that about 55% of the 1,858 specimens received higher scores than the original assignments. The scores increased from an average of 5.95 for the original readings to an average of 6.8 by contemporary standards. In addition, two other pathologists reviewed samples of the slides and also arrived at higher scores than the original readings.

The authors suggest that perhaps "pathologists are more hesitant to assign low Gleason scores to contemporary prostate needle biopsy specimens because these scores are frequently upgraded" after reviewing the whole tumor after it has been surgically removed.

The authors also suggest that with more tumors labeled with higher Gleason scores than a decade ago, many low-grade tumors are being labeled as more dangerous than they actually are. This re-labeling could skew mortality and survival rates for prostate cancer patients because those higher score categories would include patients with less aggressive forms of the disease. This statistical artifact is known as the Will Rogers phenomenon, based on a Will Rogers joke: "When the Okies moved to California, the IQ of both states went up." In research, this refers to situations in which reclassifying groups of patients changes the outcomes of both groups without changing the outcomes of all patients combined.

For example, the study found that contemporary prostate cancer mortality rates for the men in the study appeared to be 28% lower than Gleason score-standardized historical rates, even though the overall number of deaths remained the same. Such "statistical artifacts may be producing a false sense of therapeutic accomplishment," the authors write. "Unless researchers are careful, some or all of an apparent improvement in clinical outcomes that is observed when contemporary series are compared with historical series may reflect a statistical artifact--Will Rogers would probably not be amused," they conclude.

The Will Rogers phenomenon of prostate cancer presents a situation "where all the biopsies are necessary and all cancers require treatment, as all have Gleason scores above 5," write Ian M. Thompson, M.D., of the University of Texas Health Science Center in San Antonio, and colleagues in an accompanying editorial. Referring to the phenomenon as "grade inflation," they express concern that score inflation "is a component of the more insidious phenomena of overdetection and overtreatment of prostate cancer." They point out that about 75% of U.S. men have had a PSA test, and more than 17% will be diagnosed with prostate cancer during their lifetime. However, there is only a 3% to 4% lifetime risk of prostate cancer death. As many as 5 of every 6 men diagnosed with the disease may not require treatment--treatment that may negatively affect quality of life, they add.
-end-
Contacts:
Article: Jim Walker, Communications Department, University of Connecticut Health Center, walker@nso1.uchc.edu.
Editorial: Will Sansom, University of Texas Health Science Center, 210-567-2579, sansom@uthscsa.edu.

Citations:
Article: Albertsen PC, Hanley JA, Barrows GH, Penson DF, Kowalczyk PDH, Sanders MM. Prostate Cancer and the Will Rogers Phenomenon. J Natl Cancer Inst 2005;97:1248-53.
Citation: Thompson IM, Canby-Hagino E, Lucia MS. Stage Migration and Grade Inflation in Prostate Cancer: Will Rogers Meets Garrison Keillor. J Natl Cancer Inst 2005;97:1236-37.

Note: The Journal of the National Cancer Institute is published by Oxford University Press and is not affiliated with the National Cancer Institute. Attribution to the Journal of the National Cancer Institute is requested in all news coverage. Visit the Journal online at http://jncicancerspectrum.oxfordjournals.org/.

Journal of the National Cancer Institute

Related Prostate Cancer Articles from Brightsurf:

Low risk of cancer spread on active surveillance for early prostate cancer
Men undergoing active surveillance for prostate cancer have very low rates - one percent or less - of cancer spread (metastases) or death from prostate cancer, according to a recent study published in the Journal of Urology®, an Official Journal of the American Urological Association (AUA).

ESMO 2020: Breast cancer drug set to transform prostate cancer treatment
A drug used to treat breast and ovarian cancer can extend the lives of some men with prostate cancer and should become a new standard treatment for the disease, concludes a major trial which is set to change clinical practice.

Major trial shows breast cancer drug can hit prostate cancer Achilles heel
A drug already licensed for the treatment of breast and ovarian cancers is more effective than targeted hormone therapy at keeping cancer in check in some men with advanced prostate cancer, a major clinical trial reports.

The Lancet: Prostate cancer study finds molecular imaging could transform management of patients with aggressive cancer
Results from a randomised controlled trial involving 300 prostate cancer patients find that a molecular imaging technique is more accurate than conventional medical imaging and recommends the scans be introduced into routine clinical practice.

Common genetic defect in prostate cancer inspires path to new anti-cancer drugs
Researchers found that, in prostate cancer, a mutation leading to the loss of one allele of a tumor suppressor gene known as PPP2R2A is enough to worsen a tumor caused by other mutations.

First prostate cancer therapy to target genes delays cancer progression
For the first time, prostate cancer has been treated based on the genetic makeup of the cancer, resulting in delayed disease progression, delayed time to pain progression, and potentially extending lives in patients with advanced, metastatic prostate cancer, reports a large phase 3 trial.

Men taking medications for enlarged prostate face delays in prostate cancer diagnosis
University of California San Diego School of Medicine researchers report that men treated with medications for benign prostatic hyperplasia (enlarged prostate) experienced a two-year delay in diagnosis of their prostate cancer and were twice as likely to have advanced disease upon diagnosis.

CNIO researchers confirm links between aggressive prostate cancer and hereditary breast cancer
The study has potential implications for families with members suffering from these types of tumours who are at an increased risk of developing cancer.

Distinguishing fatal prostate cancer from 'manageable' cancer now possible
Scientists at the University of York have found a way of distinguishing between fatal prostate cancer and manageable cancer, which could reduce unnecessary surgeries and radiotherapy.

Researchers find prostate cancer drug byproduct can fuel cancer cells
A genetic anomaly in certain men with prostate cancer may impact their response to common drugs used to treat the disease, according to new research at Cleveland Clinic.

Read More: Prostate Cancer News and Prostate Cancer Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.