When early screening leads to risks
Radio talk show host Don Imus has plenty of company in his recent prostate cancer diagnosis: The disease strikes 1 in 6 American men.
You’d think early screening would be a key preventive tool, but two large studies, published in the New England Journal of Medicine last week, found that screening had little to no effect on how many men die from prostate cancer. Instead, the studies found, more men are getting tests and treatments they don’t need, risking side effects such as incontinence and impotence.
Growth of cancerous tumors in the prostate, the gland that produces seminal fluid in men, is often so gradual as to not affect a person’s overall health. But it also can be aggressive, breaking free and invading other parts of the body. “Prostate cancer is like the cat family. You have house cats and you have tigers,” says Dr. David Penson, a urologist at USC’s Keck School of Medicine.
Survival rates for cancer localized to the gland are nearly 100% but drop to 33% when the cancer has metastasized to other parts of the body, according to National Cancer Institute data. In the U.S., 220,000 cases of prostate cancer are diagnosed and about 27,000 men die of it each year.
It was hoped that early detection would lead to better prognosis because of earlier treatment. But with the simplest screen, a blood test for prostate-specific antigen (PSA), Penson says “there’s a high false positive rate” -- a worrisome PSA level but no cancer. “If we find prostate cancer, probably 20% to 30% are what we call overdiagnosed cases. They’re not going to affect you in your lifetime.”
There is not yet a reliable way to predict which will remain slow-growing and mostly harmless and which will become life-threatening.
Men should consult with their doctors to decide whether testing is appropriate, experts say. (The American Cancer Society does not recommend routine prostate cancer screening.) Factors such as age, race, family history and health conditions should be taken into account.
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Test scores
Should you opt for a test, here are what the results may mean:
A PSA level of 4 ng/ml means you have a 1 in 4 chance of having prostate cancer. If it’s higher than 10 ng/ml, your chances increase to 50-50. Further diagnostic tests are needed to determine whether cancer is present: a transrectal ultrasound to visualize any abnormalities in the prostate gland and a biopsy, where bits of gland are extracted with a needle to see cellular changes indicative of cancer.
It’s important to watch whether PSA levels are increasing over time, says Howard Soule, chief scientific officer of the Prostate Cancer Foundation in Santa Monica. Even if PSA levels are less than 4, “values that are creeping up are a bad thing.”
Biopsies are scored on a 10-point scale called the Gleason score, which represents how much cell growth deviates from normal. Most biopsied prostates received a Gleason score of 5 to 6 (64% of patients), which may represent a slow-growing cancer.
A Gleason score of 8 to 10 represents the greatest risk of aggressive prostate cancer (10% of patients).
But “a high percentage of guys are diagnosed with a 7,” says Dr. Mark Litwin, a professor of urology and public health at UCLA’s David Geffen School of Medicine (25% of patients). “Those are really the ones that we don’t know what to do with.” These cases are the most difficult for doctors to predict how rapidly the cancer will progress.
Clinical descriptions of prostate cancer are based on the size of a tumor and whether it has spread outside the prostate, Litwin says.
Lymph nodes and other tissues are also assessed to monitor whether the cancer is spreading. Litwin says the state-of-the-art staging scale is called TNM for tumor (on a 4-point scale, with 1 indicating the tumor is contained within the prostate and 4 indicating that it has invaded local structures around the gland), lymph node (absent or present) and metastasis (absent or present).
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Therapies
Treatment choices include surgery to remove the prostate, radiation therapy to destroy growing tumors, and watchful waiting. Treatment is usually undertaken for a Gleason score of 7 and higher or if the clinical stage is T3 to T4, which means the tumor may be escaping the prostate.
In watchful waiting, also called active surveillance, no surgery is performed. Screening tests are done every three months rather than yearly, and biopsies might be taken every six months. If there’s no change, the intervals gradually lengthen. Active surveillance may be appropriate for men with PSA levels less than 10 and Gleason scores no more than 6 and having no evidence of the cancer’s spread.
“Our tendency, at least in the U.S., is to err on the side of treatment, because we don’t want to see anyone die from prostate cancer,” Litwin says. But as the new studies show, that comes at the cost of complications from treating cancers that wouldn’t kill a person anyway.
