By Jia-Rui Chong, Times Staff Writer

December 5, 2006

The hair-loss drug Propecia interferes with the most commonly used test
for prostate cancer, causing inaccurate readings that can mask the
presence of the disease, researchers reported Monday.

About 4 million men worldwide use the
drug, whose active ingredient is finasteride, which prevents the
breakdown of testosterone. Researchers knew that the high doses of
finasteride in Proscar, the drug used to treat an enlarged prostate,
could reduce levels of the marker called prostate specific antigen, or
PSA. The new study is the first to show that the lower levels in
Propecia also lower PSA levels.

The suppression could mean that a previously safe reading on a PSA test
could be false, said Dr. David Quinn, an oncologist at USC who has
worked on previous studies on finasteride and spoken for the drug's
maker, Merck & Co., on other drugs, but was not involved with this
study.

"If people are taking Propecia, they should know the PSA may not be the
most accurate predictor of cancer," he said. "Other tests, such as the
digital rectal exam, where the doctor is feeling the prostate, may be of
more importance."
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The study, published in the Lancet Oncology, followed 308 men age 40 to
60 with male-pattern baldness. The data were collected by Dr. Claus
Roehrborn, a urologist at the University of Texas Southwestern Medical
Center while he worked with Merck on developing the drug. Merck funded
the study.
For 12 months, 247 men took 1 milligram of finasteride daily, while 61
took a placebo.

In men taking Propecia, PSA readings steadily declined. Compared with
the beginning of the study, the readings at the end were a median of 48%
lower. The effect was slightly greater on men in the 50 to 60 age group.

"Doctors often tell men that their PSA is 'normal,' but don't tell them
what the number is," he said. "They should always know what the number
is."

Roehrborn said other drugs in this class, known as 5-alpha reductase
inhibitors, will affect PSA tests in a similar way.

Prostate cancer is the most commonly diagnosed cancer in men, with about
230,000 new cases expected in 2006, according to the American Cancer
Society.
*
jia-rui.chong@latimes.com

knowledge is power - growing old is mandatory - growing wise is optional    
"Many more men die with prostate cancer than of it. Growing old is
invariably fatal. Prostate cancer is only sometimes so."
http://community.webtv.net/PALMER_ENT/doc