Anaheim, Calif. -- Successful outcomes for surgery to treat early stage lung cancer appear to depend on the level of vitamin D present in a patient - a calculation that includes food sources, supplements, as well as the season of the year during which the operation is performed, according to researchers at Harvard School of Public Health and Harvard Medical School.
Their study, presented here at the 96th Annual Meeting of the American Association for Cancer Research, shows that patients with high vitamin D intake who had surgery in months with lots of sun were more than twice as likely to be alive five years after surgery, compared to patients with low vitamin D intake who had wintertime operations.
The mechanism behind the link between vitamin D and surgery outcome is not known, and the study needs to be validated, the researchers say, but they add that a number of other studies have hinted that vitamin D may work to inhibit a variety of different cancers.
"Animal studies have shown that treatment of cancer with vitamin D demonstrates both anti-proliferative and anti-invasive properties, but we don't know if that is true in humans with cancer," says the lead investigator, Wei Zhou, Ph.D., a research scientist at the Harvard School of Public Health. "So the best way we can make some sort of association is to look at differences in what happens after treatment of cancer between patients who use high levels of vitamin D through their diet and supplements, as well as through sunlight exposure, compared to patients who do not.
"This study in no way suggests that people should try to time their cancer surgeries for a particular season - that would obviously be impossible," Zhou adds. "But, if validated, it may mean that increasing a patient's use of vitamin D before such surgery could offer a survival benefit."
The research team, led by Prof. David Christiani, M.D., of Harvard University, included investigators from Massachusetts General Hospital, Dana-Farber Cancer Institute, Brigham and Women's Hospital and Harvard Medical School, looked at the disease free survival (DFS) and overall survival (OS) in 456 patients with early stage non-small cell lung cancer. A variety of different lung tumor types were included in the mix of patients, of whom 40 percent were current smokers. Only 9 percent of patients received radiation treatment following surgery, and 1 percent received chemotherapy.
The researchers derived two separate calculations - outcome based on intake of vitamin D from food and supplements (using diet questionnaire information from 321 patients), and outcome based on the season in which the surgery was performed, which was viewed as a surrogate marker for intake of vitamin D from sunlight.
Results from the analysis of survival as it relates to season of surgery showed:
For disease free survival, the researchers found that patients who had operations in winter were about 40 percent more likely to die from their cancer, than patients who had surgery in summer. Five year disease-free survival rates were 54 percent, 56 percent, and 70 percent, respectively, for patients who had surgery in winter, spring/fall, and summer. For overall survival, patients who had surgery in the winter were about 25 percent more likely to die than those who were operated in summer. Five-year overall survival rates were 50 percent, 57 percent, and 59 percent for patients who had surgery in winter, spring/fall, and summer.
When the joint effects of surgery season and vitamin D intake were considered, the researchers found:
Patients with the highest vitamin D intake who had surgery in the summer had statistically significantly better outcomes - a three-fold better disease-free survival and a four-fold better overall survival - than patients who had surgery during winter with the lowest vitamin D intake. The five-year disease-free survival was 83 percent versus 46 percent, respectively, and the five-year overall survival rate was 72 percent compared to 30 percent, respectively.
Zhou points out that the study was conducted on patients who had surgery in Boston, and so the calculation of surgery season may differ in other locations.
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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