The Truth... What is it?





The Humphrey Formula

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(as of 8/8/08, I am not positive that I have interpreted the calculation correctly)

This calculation was developed as a tool to predict the total volume of cancerous prostate tissue and is based on the ultrasound-guided needle biopsy findings and serum PSA at about the time of biopsy. It does not know how to "back out" any PSA elevation component related to any significant coexisting prostatitis. And, it cannot guarantee that a small volume calculation of an "insignificant" tells the truth. On the other hand, if the calculation indicates a cancer of significant size (>0.5cc...>1.0cc) and the biopsies (1) failed to contain much chronic prostatitis and (2) were not from a really large gland (say, greater than 50cc) with biopsie showing a background of BPH-type benign hyperglandularity, then I'd opine that clinicians be very cautious about assigning any label of "insignificant."

Parameters:

  • total tumor length in each positive core, summed
          
  • number of positive cores (six cores taken in most cases & fewer than 4 won't work)
      
  • serum PSA level in ng/mL 

Formula:

total tumor volume in cubic cm. = (0.216) times (total cancer length sum) plus (0.0216) times [exponent = number positive cores] plus (0.137) times the PSA value

A cautionary quote from Dr. Lewis2: "Thanks for your questions.  I have to tell you that my enthusiasm for this area is not very high.  I worked on this project while I was in training. I will say that the correlation is really too 'rough' (or better said 'poor') to be really reasonable for everyday practice.  It is clear that needle biopsy does not sample enough of the prostate to be reliable as a consistent predictor of tumor burden, and there will be patients where the model is way off (high OR low). As such, I wouldn’t recommend using it for individual patients.  The more recently developed nomograms have been helpful clinically, however."

Examples:

  • 60 y/o has pre-BX PSA of 5.3 & 6 patterned cores are taken by U/S guidance; the right base had a 2mm segment of cancer and the right mid had a 3mm segment...Gleason 3 + 3 = 6. The Humphrey calculation indicates 1.806467 cc (grams)...significant.
  • 65 y/o has pre-BX PSA of 8.3 & 6 patterned cores are taken by U/S guidance; the right base had a 1mm segment of cancer, the right mid had a 1.5mm segment of cancer, and the left mid had a 2mm segment...Gleason 3 (90%) + 4 (10%) = 7. The Humphrey calculation indicates 2.1091 cc (grams)...significant.
          
  • 62 y/o has pre-BX PSA of 4.3 & 6 patterned cores are taken by U/S guidance (45cc prostate without impressive benign hyperglandularity); the right base had a 1mm segment of cancer and the right mid had a 0.53 mm segment...Gleason 3 + 3 = 6. The Humphrey calculation indicates 0.9194 cc (grams)...also likely a "significant" cancer. 


Dr. Shaw's personal WEB-FILE of info for prostate cancer patients & their "significant others"

Our pathology group's TOC WEB-FILE on prostate cancer issues

Lewis JS Jr, Vollmer RT, Humphrey PA,  "Carcinoma extent in prostate needle biopsy tissue in the prediction of whole gland tumor volume in a screening population.",
Am J Clin Path., 118: 442-450, 2002.
Lewis JS Jr, 7/23/07 e-mail response to e-mailed questions from Dr. Shaw.

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(posted 8/16/2008)