Charles Fuchs, MD, MPH
Patients diagnosed with colon cancer who had abundant vitamin D in
their blood were less likely to die during a follow-up period than those
who were deficient in the vitamin, according to a new study by
scientists at Dana-Farber Cancer Institute.
The findings of the study — the first to examine the effect of
vitamin D among colorectal cancer patients — merit further research, but
it is too early to recommend supplements as a part of treatment, say
the investigators from Dana-Farber and the Harvard School of Public
In a report in the June 20 issue of the Journal of Clinical Oncology,
the authors note that previous research has shown that higher levels of
vitamin D reduce the risk of developing colon and rectal cancer by
about 50 percent, but the effect on outcomes wasn't known. To examine
this question, the investigators, led by Kimmie Ng, MD, MPH, and Charles Fuchs, MD, MPH, of Dana-Farber, analyzed data from two long-running
epidemiologic studies whose participants gave blood samples and whose
health has been monitored for many years.
They identified 304 participants in the Nurses' Health Study and the
Health Professionals Followup Study who were diagnosed with colorectal
cancer between 1991 and 2002. All had had vitamin D levels measured in
blood samples given at least two year prior to their diagnosis. Each
patient's vitamin D measurement was ranked by "quartiles" — the top 25
percent, the next lowest 25 percent, and so on. Those whose levels were
in the lowest quartile were considered deficient in vitamin D.
The researchers followed the 304 patients until they died or until
2005, whichever occurred first. During that period, 123 patients died,
with 96 of them dying from colon or rectal cancer. The researchers then
looked for associations between the patients' previously measured
vitamin D blood levels and whether they had died or survived.
The results showed that individuals with the vitamin D levels in the
highest quartile were 48 percent less likely to die (from any cause,
including colon cancer) than those with the lowest vitamin D
measurements. The odds of dying from colon cancer specifically were 39
percent lower, the scientists found.
"Our data suggest that higher prediagnosis plasma levels of [vitamin
D] after a diagnosis of colorectal cancer may significantly improve
overall survival," the authors wrote. "Future trials should examine the
role of vitamin D supplementation in patients with colorectal cancer."
The measurements of vitamin D in the patients' blood reflected both
the amounts made by the body when exposed to sunlight and to all sources
of the vitamin in their diets, said Ng. However, she added, there may
be additional unknown factors that might account for individual
differences. Patients with the highest vitamin D levels tended to have
lower body-mass index (BMI) indicating that they were leaner, and also
were more physically active. However, after controlling for BMI and
physical activity, as well as other prognostic factors, higher vitamin D
levels were still independently associated with better survival rates.
Ng said that a trial is being planned in which colon cancer patients
will take vitamin D along with post-surgery chemotherapy to look for any
benefits of the supplements.
Meanwhile, she said that individuals with colon cancer should consult
their physicians as to whether they should add vitamin supplements to
their daily regimen. Standard recommended daily amounts of vitamin D
supplements range from 200 International Units (IU) per day for people
under age 50 to 400 IU for people between 50 and 70, and 600 IU for
those over 70.
Other authors of the study include Jeffrey Meyerhardt, MD, MPH, of
Dana-Farber; Kana Wu, MD, PhD, and Edward Giovannucci, MD, ScD, of the
Harvard School of Public Health; Diane Feskanich, ScD, of Brigham and
Women's Hospital, and Bruce Hollis, PhD, of the Medical University of
The research was supported by grants from the National Cancer Institute.
Dana-Farber Cancer Institute (www.dana-farber.org)
is a principal teaching affiliate of the Harvard Medical School and is
among the leading cancer research and care centers in the United States.
It is a founding member of the Dana-Farber/Harvard Cancer Center
(DF/HCC), designated a comprehensive cancer center by the National