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Saturday, January 28, 2012

Prostate cancer: to screen or not to screen

For several years there have been conflicting signals from physicians and researchers about whether to screen for prostate cancer with a PSA test. Here's my take.

Begin by understanding that prostate cancer can be cured only when it is detected and treated prior to metastasis. The progression of metastatic prostate cancer can be delayed for quite some time, but if you live long enough -- for example, you're in your 50's and otherwise healthy when metastasis occurs -- it will almost certainly kill you. New treatments for metastatic prostate cancer are becoming available, but middle-age men shouldn't gamble that these new treatments will salvage them.

I had a routine PSA test at age 51. It signaled an aggressive but asymptomatic prostate cancer (Gleason 4+3, initial PSA 13 rising steadily to 22 in four months). By the time I underwent surgery, the tumor had moved beyond the prostate: the prelude to metastasis. As my primary care physician put it recently, without diagnosis "it probably would have been your demise by now."

Thankfully, I have been cancer-free for five years. Having gone this long without a recurrence, the likelihood of a recurrence someday is small although not zero. Even if it does recur, treatment will have provided me extra years of fruitful life.

If PSA screening can save lives like mine, what's the problem? PSA screening doesn't have many false negatives, but it has a lot of false positives because common conditions other than cancer can drive PSA up. When a PSA test indicates a problem, a biopsy usually ensues. The biopsy is unpleasant at best and agonizing at worst, carries a non-negligible risk of complication, and has a substantial false negative rate -- meaning that a second biopsy is sometimes performed. Lastly, the biopsy is costly.

Suppose the biopsy shows malignancy. Most prostate cancers, unlike mine, are slow-growing and pose no immediate danger. The older a man is, the more likely his prostate cancer will never pose a problem; the guy will die of something else first. Anxious men who get their prostate cancer treated too early run a high likelihood of life-long side effects of treatment (that I have); they also bear the risks that treatment itself will cause other problems. And of course, treatment is expensive and can lead to a lot of downtime, depending on the breaks.

All these factors argue against blanket PSA screening; but the indisputable fact is that occasionally, as in my case, PSA screening will save lives. I am not a physician, but here is how I see it:

  • If you have a family history of prostate cancer (as I did), get a PSA test by age 50. If you are African-American with a family history, get tested by at age 45. If you have no family history of prostate cancer and have no prostate symptoms, don't go much past 55.
  • If your PSA is non-zero, don't panic. Follow a course of "watchful waiting" until the PSA gets to 8 or jumps rapidly (or your prostate becomes symptomatic). 8 is a higher cutoff than most urologists would advise, but you want to avoid the practice of defensive medicine and the consequences of unnecessary treatment. Use the excellent online prediction tools provided by Memorial Sloan-Kettering to learn the probabilities.
  • If your PSA gets into double-digits and continues rising, you are clearly at moderate risk of progressing to metastatic disease -- unless you are more likely die of something else, including old age. Have a long discussion with both a urologist and a radiation oncologist to decide what's best for you.
What we need is a better test than PSA. Researchers are working on it. In the meantime, I'm grateful that the PSA test does exist. Unlike women whose breasts can be palpated or imaged, prostates are inaccessible and rarely indicate problems on images.