Download 50 incidence of clinically indolent PCa versus a rate of 14.6 in

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PREDICTION OF INDOLENT PROSTATE CANCER
FIG. 5. Nomogram for full model. Pre.Tx., pretreatment. Clin., clinical. Pri.Bx.Gl, primary biopsy Gleason score. Sec.Bx.Gl, secondary
biopsy Gleason score. U/S, ultrasound. Prob., probable.
50� incidence of clinically indolent PCa versus a rate of
14.6� in those found to have PCa on first biopsy.21 Indolent
PCa also appears to be more common in men with free/total
PSA 0.15 or greater.8 We did not have sufficient data to
incorporate the number of previous negative biopsies or free/
total PSA in our modeling but these factors may be useful in
future research.
We developed these nomograms for predicting the possibility that a man has an indolent cancer. The base model requires minimal data input, while the full model requires
considerable analysis of systematic biopsy. The base model
appears to be better calibrated (fig. 2), which means that for
a group of patients the mean predicted probability is close to
the proportion of men with indolent cancer. However, the full
model is more discriminating (table 2), which means that it
can better rank individual patients with respect to risk.
Ideally, then, one would use the full model to obtain a predicted probability for the patient, and then adjust the
prediction to correct for the calibration error. We plan to
incorporate this adjustment in our free software, which
can be obtained at www.nomograms.org.
New models were developed to distinguish indolent from
clinically important cancer with relatively high areas under
the ROC curve (0.64 to 0.79). However, these models may be
more useful for ruling out, rather than ruling in, indolent
cancer, given that they rarely predict with very high probabilities. The nomograms would be useful for counseling the
man with low predicted probability of indolent cancer, reassuring him that aggressive therapy appears warranted. Currently, a watchful waiting policy for a man with indolent
cancer is determined subjectively based on disease characteristics, health and patient preferences. Our nomogram may
provide a useful tool for assisting in this decision. Although
the nomogram accurately discriminates between men with
and without indolent cancer, the tool is insufficient by itself
to direct a man toward watchful waiting. For example, an
indolent cancer in an older man may be considered ideal for
conservative management but an indolent cancer in a young
man may still warrant aggressive therapy, since the patient
may have a long life expectancy during which the cancer may
progress from its present, presumably indolent, state. With
this nomogram, we can only hope to provide objective information for use as a basis for this decision, rather than provide an absolute solution to the management dilemma.
CONCLUSIONS
Nomograms have been developed to predict the probability
that a man with prostate cancer has an indolent tumor. They
each appear to have excellent discriminatory ability and good
calibration.
Drs. Kazuho Suyama, Takuji Utsunomiya, Shigehiro Soh
and John Gore at Baylor College of Medicine, and Drs. Peter
G. Hammerer, Alexander Haese and Rolf-Peter Henke at
Hamburg University Hospital helped collect the data.
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Scardino, P. T.: The pathological features and prognosis of
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J Urol, 152: 1714, 1994
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