What is PSA Velocity?
Basically, PSA velocity is the rate at which your PSA level increases from year to year.
Let’s say you have the following PSA values over time:
- January 2008: 1.4 ng/ml
- January 2009: 1.9 ng/ml
- January 2010: 1.9 ng/ml
- January 2011: 3.1 ng/ml
- April 2011: 3.6 ng/ml
Then what is your PSA velocity?
If we make the assumption that your PSA was stable at the initial value of 1.4 ng/ml, then your PSA velocity is an increase of
3.6 – 1.4 = 2.2 ng/ml over 39 months = 0.68 ng/ml per year.
On the other hand, if we assume your PSA was still stable at 1.9 ng/ml, then your PSA velocity is
3.6 – 1.9 = 1.7 ng/ml over 15 months = 1.36 ng/ml per year.
In other words, your PSA velocity depends on the PSA values you have available and over what length of time. In the example given above, an alternative way to look at the data is to ask what this patient’s PSA velocity has been over the past year. This would appear to be approximately
3.6 – 1.9 = 1.7 ng/ml over 12 months = 1.36 ng/ml per year.
However, we can’t tell precisely because we do not know his PSA level in April 2010.
We aren’t going to even try to get into all the theories about the “right” way to measure PSA velocity. It is way too complicated and may not even matter that much. There is a PSA velocity calculator available on a University of California web site. Enjoy!
Does PSA Velocity Affect Prostate Cancer Risk?
There are two very different theories about this.
One group, represented by Dr. William Catalona and colleagues, believes that PSA velocity is a strong indicator of risk for aggressive prostate cancer, and that men with a rapidly rising PSA are at greater risk for aggressive disease that needs treatment than men with a slowly rising PSA.
Another group, represented by Andrew Vickers and colleagues, believes that PSA velocity is irrelevant to prostate cancer risk by comparison with other available data, and that we don’t need the PSA velocity to tell us who is at risk because we already know.
The “New” Prostate Cancer InfoLink is neutral. We believe that it should be possible to resolve this issue fairly easily with the right data analysis (see discussion on blog entry from June 2008). However, such an analysis has not been carried out and published so far, and until it is carried out and published, the controversy will continue, so here are the positions of the two different groups:
Catalona et al.: “PSA Velocity Is Important”
Dr. Catalona states on his web site that, “One of the big but unanswered questions about prostate cancers is: Which ones are aggressive and which ones are not?”
Based on a paper by D’Amico et al., published in 2004, Dr. Catalona argues that:
- The PSA velocity, prior to diagnosis of prostate cancer, is a more powerful indicator of eventual recovery or death from prostate cancer than the actual PSA level itself.
- The results of this study indicate that men with a high PSA velocity should not be managed by “watchful waiting,” because this could be especially harmful if the cancer is fast-growing.
- Their data suggest that a rapid rise in the PSA score is a sign the cancer is particularly aggressive, and that some men with prostate cancer and a high PSA velocity will require more than a radical prostatectomy to prevent prostate cancer death.
He goes on to state that:
- PSA velocity measurements during the year before the diagnosis of prostate cancer can help identify the potential aggressiveness of the cancers.
- Men with a PSA increase of 0.75 ng/ml within a year show a worrisome risk for prostate cancer.
- Men with a PSA increase of 2.0 ng/ml within a year are more likely to have an aggressive cancer with a higher potential risk for death.
- If the PSA level increases slowly before surgery, then treatments are most effective and patients have little chance of dying from the cancer.
- When PSA levels rose by ≥ 2 ng/ml during the year before surgery, about one in six of those patients died from prostate cancer within 7 years.
He concludes by noting that, although the relative risk of death from prostate cancer was nearly 10 times greater in the higher PSA velocity group, other variables were important as well. PSA can also rise because of BPH or prostatitis, so when the PSA does begin to rise, men should be treated with antibiotics to see if the PSA will return to normal before proceeding to biopsy.
Vickers et al.: PSA Velocity Is Irrelevant”
In a guest blog on this web site, Dr. Vickers laid out his position with equal clarity, by posing the following question from a patient to his doctor: “My PSA is low, but has been rising over the past few years. Should I consider a biopsy?”
He then answered that question as follows:
- Many groups currently recommend that men who experience a rise in PSA should consider biopsy even if their PSA level is low. As one example, the American Cancer Society suggests that a PSA velocity of 0.35 ng/ml/yr “may be a cause for concern” in men with low PSAs.
- This implies that Mr Brown, who had a PSA of 1.6 ng/ml in 2007, and a PSA of 2.0 ng/ml in 2008, should think about a biopsy even though he is below any of the usual PSA cut-points (such as 2.5 or 4 ng/ml).
- A serious problem with guidelines of this type, however, is that there is actually very little evidence to support them. To obtain suitable evidence, researchers would have to biopsy a very large number of men with low PSAs and then correlate their changes in PSA with the results of their biopsies. This isn’t often done, for ethical reasons. So, researchers who think PSA velocity is potentially important have extrapolated from the available data by assuming, for example, that men who were not biopsied did not have cancer, or that men diagnosed with prostate cancer would have had a positive biopsy (had one been conducted) 10 years before their diagnosis.
- Only one study has ever systematically biopsied men with low PSAs and then looked at whether PSA velocity actually predicts whether a man has cancer. This was the Prostate Cancer Prevention Trial, in which all 18,800 men enrolled were biopsied because it was thought that finasteride might lower PSA without lowering the risk of cancer. The conclusions of the authors of this trial were unequivocal: once you took PSA level into account, PSA velocity did not help to identify men who might be more or less appropriate for biopsy.
- Other studies in men with higher PSA levels have had similar conclusions; indeed, one study found that men with a rapidly rising PSA were less likely to have prostate cancer, presumably because the rise in PSA was likely due to infection or inflammation of some type.
Vickers concluded that, when deciding whether or not to have a biopsy, the two key things to think about are your PSA level and your doctor’s advice. He stated that in his and in many of his colleagues’ opinions, PSA velocity is not a relevant risk factor.
The “New” Prostate Cancer InfoLink cannot tell you which is the correct answer to this controversy (any more than we can to the other half of this issue, which is the question of whether PSA velocity prior to a biopsy is critical to prognosis once the biopsy data are available). On the other hand, we can advise readers that PSA velocity has clearly been shown to be predictive of risk for progression after first-line treatment.