Many physicians who treat men with prostate cancer routinely order bone scans in an effort to predict the likelihood of bone metastases. According to Gerald Chodak, MD, of the Prostate and Urology Health Center at Weiss Memorial Hospital in Chicago, Illinois, a large number of these scans are unnecessary.
He believes that in the absence of other indicators of metastasis, bone scans give little useful information in men with early-stage prostate cancer. He based his assertion on data from the ongoing Early Prostate Cancer (EPC) study, which involves more than 8,000 men with nonmetastatic disease. An analysis has clearly shown that for men who have undergone radical prostatectomy or radiation therapy, bone scans are not warranted unless prostate-specific antigen (PSA) levels exceed 5 ng/ml. When “watchful waiting” is the chosen course, a bone scan is unnecessary unless the PSA exceeds 20 ng/ml, Dr. Chodak said.
“Many clinicians are ordering [the scans] if the PSA increases over two to three visits, even if the actual PSA level is low. They’re ordering the test because they’re afraid not to,” Dr. Chodak continued. “It is understandable to want to rule out metastasis before starting treatments, but this [bone scan] is not the test to get.”
Dr. Chodak’s study included 8,113 men; 4,061 of them were randomly assigned to receive placebo, and 4,052 were assigned to receive canadian bicalutamide 150 mg/day, in addition to radiation therapy or prostatectomy. The men were observed for a median of 5.4 years. A total of 5,048 patients underwent pre-treatment bone scans. There were 148 positive scans (2.9%) in the patients taking placebo. In those patients whose baseline PSA was below 5 ng/ml, the rate of positive scans was only 0.8%. The number jumped to 3.5% in men whose PSA ranged from 10 to 20 ng/ml and rose further to 6.3% with PSAs in the range of 20 to 50 ng/ml. There were slight variations, depending on whether patients had radiotherapy or surgery, but the overall pattern was the same for all treatment groups.
Patients receiving bicalutamide generic had a lower overall positive scan rate of 1.6%. When the PSA was under 5 ng/ml, the positive scan rate was 0.4%. This figure increased to 6.3% among the men in the 10- to 20-ng/ml range, and it rose further to 11.6% for those with PSAs in the range of 20 to 50 ng/ml.
In summary, Dr. Chodak held that the positive scan rate among the men with low PSAs was too small to justify the high cost of tests that nearly invariably come back negative. Pointing out that there is no definitive method for predicting or ruling out bone metastases in men with early-stage prostate cancer, Dr. Chodak speculated:
“It may turn out that PSA doubling may be the best criterion. If your PSA doubles in less than six months, there’s an increased risk of bone metastases, but we have no randomized trials yet.”
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He said that the EPC study showed that bone scans are largely pointless if the PSA is less than 5 in treated patients or below 20 in untreated men.