A new study suggests that the commonly accepted threshold for prostate-specific antigen (PSA) levels may miss a large number of prostate cancers.
Rinaa S. Punglia, M.D., of Harvard Medical School in Boston, and her colleagues used a mathematical model to correct for verification biasa phenomenon in which men with positive PSA findings are more likely to be recommended for a prostate biopsy than men with negative PSA findingsin a cohort of 6,691 men who underwent PSA screening.
If the threshold PSA value for undergoing biopsy were set at 4.1 ng/mL, the researchers estimate that 82% of prostate cancers in men under age 60 and 65% of prostate cancers in men age 60 and older would be missed. Lowering the threshold from 4.1 ng/mL to 2.6 ng/mL in men under the age of 60 would double the cancer-detection rate from 18% to 36%. In men age 60 and older, lowering the threshold from 4.1 ng/mL to 2.1 ng/mL would increase the cancer-detection rate from 35% to 68%. The study appeared in the July 24 issue of the New England Journal of Medicine.
In an accompanying editorial, Fritz H. Schröder, M.D., Ph.D., and Ries Kranse, Ph.D., of the Erasmus Medical Center in Rotterdam in The Netherlands, cautioned that lowering the PSA threshold level would increase the rate of overdiagnosis and, potentially, overtreatment. In fact, the study found that lowering the biopsy threshold to 2.6 ng/mL tripled the number of unnecessary biopsies from 2% to 6%.
See News, Vol. 94, No. 6, p. 415, "Value of Prostate-Specific Antigen: Are Higher Levels Meaningful?"
Study Faults Food Surveys in Risk Analyses
Case-control studies have consistently found an association between fat intake and risk of breast cancer, yet cohort studies have been unable to show such an association. A new study suggests that the negative findings may result from the use of inherently imprecise food-frequency questionnaires, which are based on a persons recollection of their dietary habits.
Sheila A. Bingham, Ph.D., of the MRC Dunn Human Nutrition Unit in Cambridge, U.K., and her colleagues examined fat intake by 13,070 women with both a food-frequency questionnaire and a detailed 7-day food diary. Between 1993 and 1997, 168 women developed breast cancer. Each woman was compared with four healthy controls matched for age and other potential risk factors.
Based on the food diary, women in the top 20% of saturated fat consumption were at a 2-fold increase in risk of breast cancer compared with women in the lowest 20% of saturated fat intake. No such association was seen between increased saturated fat intake and breast cancer risk when using the food-frequency questionnaire.
The study appeared in the July 19 issue of The Lancet.
Antioxidant Trial Findings Hold Up, Post-Trial Follow-Up Finds
A 6-year follow-up study of the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study reports that the apparent benefits from alpha-tocopherol (vitamin E) and the increased risk of lung cancer from beta-carotene are no longer evident.
The ATBC Study looked at 29,133 male smokers and found that supplementation with alpha-tocopherol had no effect on lung cancer risk but appeared to decrease the risk of prostate cancer. Beta-carotene supplementation was associated with an increase in risk of lung cancer.
Researchers conducted a postintervention follow-up to determine the duration of the intervention effects and to see if there were any late effects of the antioxidants. During the 6-year follow-up period, there were 1,037 new cases of lung cancer and 672 new cases of prostate cancer.
There was no difference in lung cancer incidence between people who received alpha-tocopherol and those who did not receive the supplement. There was also no difference in lung cancer incidence between people who did and did not receive beta-carotene supplements. In addition, there was no difference in prostate cancer incidence between people who received alpha-tocopherol and people who did not receive the supplement. The study appeared in the July 23/30 issue of the Journal of the American Medical Association.
Linda Wang
![]() |
||||
|
Oxford University Press Privacy Policy and Legal Statement |