We read with interest the recent practice guidelines on prostate cancer published by the National Comprehensive Cancer Network (NCCN) in a supplement to the November 1996 issue of ONCOLOGY (pp 265-288). The establishment of such guidelines is an important step in moving clinical practice in the direction of "evidence-based medicine." Due to increasing concerns regarding containment of medical costs and a desire to provide the best care to patients, it is becoming increasingly important to base clinical decision-making on rigorous analyses of available data.
Although we agree with much of the management algorithm for prostate cancer outlined by the NCCN Prostate Cancer Practice Guidelines Panel, we would like to comment further on the use of abdominal/pelvic CT or MRI in prostate cancer staging. We agree with the panel's statement that "computed tomography and magnetic resonance imaging of the abdomen and pelvis have proven to be of little value in the detection of pelvic lymph node metastasis and/or seminal vesicle invasion." The authors also state that such studies should be used in patients with T3 or T4 tumors. They do not cite any literature to support the latter statement. It is our view that T-stage alone may not be the best criterion for selecting prostate cancer patients for staging abdominal/pelvic CT/MRI.
Two Recent Studies
We recently completed two studies that examined the ability of serum prostate-specific antigen (PSA) to predict the results of staging abdominal/pelvic CT/MRI.[1,2] In our most recent analysis, 425 newly diagnosed prostate cancer patients had a mean serum PSA of 22.1 ng/mL. Approximately 28% of the group had T3 or T4 tumors on digital rectal examination. A total of 14 patients (3.6%) presented with a positive abdominal/pelvic CT/MRI (12 with adenopathy, 1 with a renal cell tumor, and 1 with an adrenal metastasis). Of these 14 patients, 11 (79%) had a serum PSA of 30 mg/mLor more (range, 30.0 to 234 ng/mL). Not all patients had T3 or T4 tumors. One-quarter to one-third of patients had disease confined to the prostate on examination. In fact, of three patients with positive scans and serum PSAs less than 20 ng/mL, two had T2 tumors. Overall, fewer than 1.0% of patients with a serum PSA less than 20 ng/mL had a positive scan.
At present, very few data are available on which to base guidelines for the use of staging abdominal/pelvic imaging in patients with newly diagnosed prostate cancer. Although our data are quite limited, we feel that serum PSA, possibly in conjunction with other parameters, may prove to be a better guide for selecting patients for radiographic staging than is T-stage alone.
A large percentage of patients with newly diagnosed prostate cancer continue to undergo staging abdominal/pelvic imaging. Such studies are not only time consuming but also costly (more than $1,000 per scan). We strongly believe that much further investigation is needed to more clearly define the appropriate indications for these studies.
We understand that the practice guidelines outlined by the authors are in a constant state of revision. Nonetheless, we would not consider the use of these radiographic staging studies in this clinical context as "uncontested and generally accepted by all authorities," ie, a level 1 recommendation. Rather, given the lack of hard supportive data, we would characterize this question as one requiring further analysis for firm recommendations (ie, a level 3 recommendation).
Michael Huncharek, MD, MPH
Assistant Medical Director,Metaworks Inc, and Adjunct Assistant Professor, Boston University School of Public Health
Joshua Muscat, MPH
Senior Epidemiologist, Division of Epidemiology, American Health Foundation, New York
The NCCN Panel Chairman Responds
The NCCN Prostate Cancer Practice Guidelines Panel agrees that emerging data may better define how to select patients for further staging studies based on defined risk for identifiable metastasis. Nomograms may become necessary for this, rather than just clinical stage, PSA, or tumor grade. In a retrospective study published in Urologic Oncology, Konety et al conclude that CT scanning has minimal to no utility in detecting extraprostatic disease in patients with clinically localized prostate cancer.
Laurence H. Baker, DO
Chairman, NCCN Prostate Cancer Practice Guidelines Panel, Professor of Medicine, Director for Clinical Research, University of Michigan Comprehensive Cancer Center, Ann Arbor