Screening for prostate cancer is controversial and very likely will be for the foreseeable future, or at least until better tools are available to suss out which cases of cancer need aggressive treatment and which are unlikely to cause harm and thus can be monitored or left alone. Plenty of researchers are working hard in pursuit of that goal; some are using so-called variants on or derivatives of the prostate-specific antigen test, and others are going in different directions entirely. Here's a rundown:
Using PSA differently. Right now the American Cancer Society recommends that physicians discuss the pros and cons of screening with the PSA test with male patients age 50 and up, if they're at average risk (and at a younger age if they're at higher risk). For those who opt for screening, the society says that men whose PSA levels are less than 2.5 ng/mL can be screened every other year rather than annually. But there is another way to use the test, says Andrew Vickers, an associate attending research methodologist at Memorial Sloan-Kettering Cancer Center in New York. Research conducted in Sweden suggests that a reading taken at a young age, between 45 and 50, "is an extremely good predictor of whether you're [at] a long-term risk of having a 'bad' prostate cancer," says Vickers. In fact, after tracking the Swedish men for years, he and other researchers found that about 80 percent of subsequent advanced cancers occurred in men who had higher-than-usual PSA levels at a young age. In other words, the PSA test can help determine not only who might have prostate cancer now but who might get it in the future and therefore should receive the test regularly.
[To explore two sides of the PSA debate, read Benefits of PSA Test Are Exaggerated and PSA Cancer Screening, Much Like a Seat Belt, Is a Wise Choice for Men]
PSA velocity. This is the rate of increase in the PSA value from year to year, and as the ACS noted in its updated guidelines, a PSA velocity of more than 0.75 ng/mL per year "was associated with a higher risk of prostate cancer" even if the PSA value itself was within normal ranges. But still, the ACS said it "does not recommend routinely incorporating PSA velocity into prostate cancer screening strategies." Why? Mostly, it said PSA velocity, when considered with the PSA value and other risk factors such as race, earlier biopsy results, and family history, doesn't add much to the ability to predict whether a given man is at risk of developing either aggressive prostate cancer or the disease in any form. So measuring the PSA velocity isn't going to do much to solve the essential dilemma of prostate screening: figuring out which men should be sent for a biopsy and treated aggressively for whatever cancer is there and which might be observed, either before getting that biopsy or after learning there is some cancer present.
Of course, much like the PSA test, PSA velocity has stirred controversy. William Catalona, a urologist who initially showed that the PSA test can be used as a first-line screening tool, is now director of the clinical prostate cancer program of Northwestern University's Robert H. Lurie Comprehensive Cancer Center. He says PSA velocity can help rule out inflammation, a common cause of PSA false alarms. If there's a significant spike in PSA, a physician could either treat the patient with an antibiotic and repeat the test (something Catalona doesn't recommend lightly given concerns over antibiotic resistance) or simply wait six weeks and check the level again. "When you have a parameter of PSA velocity shown by many investigators to be associated with an ultimate risk of dying, it's a very valuable thing to use," he says.
Free PSA. PSA exists in two forms: unbound to other proteins ("free") or bound to other proteins. The higher the percentage of free PSA as a part of total PSA, the less likely it is that cancer is present and the more likely the PSA is instead elevated owing to benign prostate hyperplasia, or BPH, says Catalona. If the figure is greater than 25 percent, there's only about a 1 in 10 chance that a biopsy would show cancer, says Catalona. (The American Cancer Society says physicians disagree on where to draw the line using free PSA but that it generally ranges between 10 percent and 25 percent; any lower than that, and you're sent for biopsy.)
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