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Equation of Pisansky et al for Predicting the Likelihood of Metastases to Seminal Vesicles and/or Pelvic Lymph Nodes in a Patient with Prostate Cancer

Purpose: To estimate the likelihood that a man with clinically localized prostate cancer will have metastases to the seminal vesicles and/or pelvic lymph nodes.

Description

Pisansky et al used an equation to predict the probability that a patient with clinically localized prostate cancer will have involvement of the seminal vesicles or metastases to pelvic lymph nodes. This can be used to help determine if a patient selected for brachytherapy should also receive external beam irradiation. The authors are from the Mayo Clinic.


Selection: Men with prostate cancer confined within the prostate.

 

Parameters:

(1) TNM classification

(2) serum PSA level

(3) Gleason score (sum of the 2 primary Gleason Grades from 1 to 5)

 

Parameter

Finding

Points

TNM classification

T1 N0 M0 (not palpable or visible on imaging)

0

 

T2a N0 M0 (one half of one lobe)

0

 

T2b N0 M0 (more than one half of one lobe but not both lobes)

1

 

T2c N0 M0 (both lobes)

1

Gleason score

<= 6 (2 to 6)

0

 

>= 7 (7 to 10)

1

 

X =

= (0.97 * LN(serum PSA)) + (1.22 * (points for Gleason score)) + (1.01 * (points for tumor stage)) - 5.17

 

likelihood of extension =

= EXP(X) / (1 + EXP(X))

 

Predicting Likelihood

Sensitivity

Specificity

False Negatives

>= 5

89% (85-92%)

50% (42-56%)

11% (8-15%)

>= 10

72% (66-78%)

73% (68-77%)

28% (22-34%)

>= 15

58% (51-64%)

83% (81-86%)

42% (36-49%)

>= 20

49% (41-56%)

89% (87-91%)

51% (44-59%)

from Table 3, page 518


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Specialty

Objective

ICD-10