Glen Tisman, MD: Nomograms – Probability of Extracapsular Extension

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Nomogram 1
Probability of Extracapsular Extension

Nomogram 1 was constructed by Ohori et al.1 It attempts to predict the side specific probability of extracapsular extension of tumor (ECE) in radical prostatectomy (RP) specimens based on the clinical features of the cancer. Though extracapsular extension is not a contraindication to surgical removal of the gland or to radiation therapy, tumors that penetrate the prostate capsule to a significant degree are associated with a higher relapse rate.

The study group consisted of 763 patients with clinical stage T1c-T3 prostate cancer who were diagnosed by systematic needle biopsy and subsequently treated with radical prostatectomy. Variables associated with ECE were clinical T stage, the highest Gleason score in any core, percent positive cores, percent cancer in the cores from each side, and PSA. Ohori constructed and internally validated nomograms to predict the side specific probability of ECE based on logistic regression analysis. Overall, 30% of the patients and 17% of 1,526 prostate lobes (left or right) had ECE. The resulting nomograms were internally validated and had excellent accuracy. Ohori concluded that standard clinical features of prostate cancer in each lobe (PSA, palpable induration and biopsy Gleason score) could be used to predict the probability of ECE in RP specimens. He felt that predictive Nomogram 1 was sufficiently accurate for use in clinical practice.

The following scenario 1 illustrates how to enter data into Nomogram 1 (follow the arrows indicating point values for each parameter/variable) to calculate the probability of extracapsular extension.

Clinical scenario 1

Clinical scenario 1: Using nomogram 1, a patient with prostate cancer clinical stage T2a (28 points) with tumor of the left lobe with biopsy Gleason score = 4+3 on the left side (55 points) and PSA = 20 ng/ml (= 78 points) will have a total of 161 points. According to Nomogram 1, this patient has a predicted 64% probability of extracapsular extension of tumor through the left lobe of the prostate.

1. Ohori, M, Kattan MW, Koh H, Maru N et al: Predicting the presence and side of extracapsular extension: a nomogram for staging prostate cancer. The Journal of Urology, Vol. 171, 1844–1849, 2004.

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