MONDAY, April 21 (HealthDay News) -- Certain biases may
compromise the findings of observational studies that compare the
outcomes of different cancer treatments, a new study shows.
Researchers at the University of Texas M.D. Anderson Cancer
Center in Houston said observational studies should include more
thorough information and should be better designed to minimize
inaccuracies.
Randomized clinical trials -- in which patients are randomly
selected to receive different treatments or a placebo -- are
considered the gold standard for determining the effectiveness of
new cancer treatments, according to background information in the
study. Observational studies involve analysis of population-based
data to determine how well patients respond to particular
drugs.
In this study, the researchers looked at the effectiveness of
different cancer therapies for prostate and colon cancer by
examining data from the Surveillance, Epidemiology and End Results
(SEER) Tumor Registry, a U.S. national population-based cancer
registry.
In all cases, the researchers came up with improbable results.
They said this shows how easy it is to generate questionable
findings when doing an observational study.
They said the skewed results in their three analyses were caused
by selection biases when cancer patients are treated. Selection
bias can occur when patients with poorer prognoses are more likely
to receive a more effective drug, or when patients with better
underlying health are more likely to receive a more toxic
treatment, because they're more likely to be able to tolerate
it.
The researchers said their findings "suggest that the results of
observational studies of treatment outcomes should be viewed with
caution."
At a minimum, researchers analyzing observational data should
attempt to separate patient outcomes into those that could possibly
be due to treatment versus those that could not, the study authors
concluded. They noted that many observational studies on cancer
treatments only report death rates from all causes and don't
specify cancer-related deaths.
The study is published in the June 1 issue of
Cancer.
More information
The U.S. National Cancer Institute has more about
cancer clinical trials.
