Predicting Latent or Indolent Tumors of Low Biological Aggressiveness
Men diagnosed with clinically localized prostate cancer have a number of treatment options available, including watchful waiting, radical prostatectomy, and radiation therapy. With the widespread use of PSA testing, prostate cancers are being diagnosed earlier in their natural history, with many tumors being small and of little health risk to the patient, at least in the short term. One of Michael Kattan’s4 many useful nomograms (illustrated as Nomogram 4) may be used to determine the likelihood that a patient’s tumor would have low biological aggressiveness (so called latent tumors that do not require immediate radical therapy). To better counsel men diagnosed with prostate cancer, he developed this statistical model that accurately predicts the presence of small moderately differentiated, prostate confined cancer based on serum PSA, clinical stage, prostate biopsy Gleason grade and ultrasound volume.
This analysis included 409 patients diagnosed by systematic needle biopsy with clinical stages T1c or T2a, N0 (lymph node negative) or NX (lymph node status unknown), and M0 (absence of distant metastases) or MX (distant status of metastases unknown) prostate cancer. They were treated solely with radical prostatectomy.
Additional biopsy features included the number and percentage of biopsy cores
involved with cancer and high-grade cancer, in addition to total length of biopsy cores involved. Indolent cancer was defined as pathologically organ-confined cancer 0.5 cc or less in volume and without poorly differentiated elements. Logistic regression was used to construct several prediction models and nomograms.
Overall 80 (20%) of the patients had indolent cancer. Nomogram 4 predicted the presence of an indolent cancer with discrimination (area under the receiver operating characteristics curves) for various models ranging from 0.64 to 0.79. Calibration of the models appeared good.
Kattan concluded that nomograms incorporating the pretreatment variables (clinical stage, Gleason grade, PSA, and the amount of cancer in a systematic biopsy specimen) can predict the probability that a man with prostate cancer has an indolent tumor and hence is at little health risk. Nomogram 4 has good discriminatory ability and calibration, and may benefit the patient and clinician when the various treatment options for prostate cancer are being considered.
Clinical scenario 4: Using Nomogram 4, a patient with a pretreatment PSA of 3.5 ng/ml (42 points), with clinical stage T1c (0 points), with biopsy Gleason’s score = 3+2 = (0 points) + (5 points),with ultrasound volume of the prostate = 60 cc (23 points),with total length in mm of cancer in all biopsy cores = 6 mm (30 points),and total length in mm of benign tissue in all cores = 45 mm (3 points) Has a total of 103 points. The probability of this patient having an indolent (or so-called latent) cancer would be approximately 18%.
4. Kattan MW, Eastham JA, Wheeler TM, et al: Counseling men with prostate cancer: A nomogram for predicting the presence of small moderately differentiated, confined tumors. The Journal of Urology, Vol. 170, 1792–1797,November 2003.