Doubling Times and PSA acceleration - Part II

[janebob99]

This is a more realistic schematic plot of PSA levels increasing over time at an ever faster rate (acceleration).

What could cause this?

My theory is that as the tumor grows, the number of androgen receptors (ARs) increases proportionally. That makes sense...more PCa cells inside a tumor...more ARs available to make more PCa cells, and so on. The number of PCa cells grows exponentially (until stopped by ADT, RP, or radiation treatment). PSA levels can reach as high as 2500 ng/mL in men with metastatic PCa. Yikes !

Instead of being a straight line in the previous linear plot (Part I), a more realistic PSA growth curve is actually parabolic (or, more accurately, exponential) with time. For the first 4 months, in this example, the PSA growth curve is essentially linear, because the tumor is very small. But as the tumor grows larger, the PSA increase over time accelerates and increases faster and faster. (This is true even when the testosterone level is constant).

This is the basis behind the Doubling Time (DT) measurement. The DT is the time interval over which the PSA doubles. In this example, the PSA at point A = 10 ng/mL, and PSA at point B = 20 ng/ml. The time between points A and B is (15-12) = 3 months. So, the doubling time = 3 months at this point in time (midpoint time = 13.5 months).

The shorter the doubling time, the more "aggressive" the prostate cancer is. Doubling times less than 8-9 months indicate that there is a high probability a tumor is growing inside the prostate. Doubling times 12 months indicate a slower growing tumor.

Men should plot their PSA versus time, so that the doubling time can be calculated. You can use the DT calculator at:

mskcc.org/nomograms/prostat...

Decreasing the testosterone levels to sub-castrate levels (T < 10 ng/dL) are the best way to stop this rapid rise in PSA over time. This can be accomplished by chemical castration by either Lupron-based ADT or transdermal estrogen (TDE) therapy (or both).

Chemical castration with transdermal estrogen (patch or gel) eliminates most of the bad side effects associated with Lupron ADT. Side effects of TDE iclude increased gynecomastia (breast enlargement), decreased muscle mass and strength, and increased risk of breast cancer. Men considering TDE should have their BRCA 1/2 gene status checked. See PROMISE registry for a free saliva test.

prostatecancerpromise.org

Bob