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:
When the joint effects of surgery season and vitamin D intake were considered, the researchers found:
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.
Founded in 1907, the American Association for Cancer Research is a professional society of more than 24,000 laboratory, translational, and clinical scientists engaged in all areas of cancer research in the United States and in more than 60 other countries. AACR's mission is to accelerate the prevention and cure of cancer through research, education, communication, and advocacy. Its principal activities include the publication of five major peer-reviewed scientific journals: Cancer Research; Clinical Cancer Research; Molecular Cancer Therapeutics; Molecular Cancer Research; and Cancer Epidemiology, Biomarkers & Prevention. AACR's Annual Meetings attract more than 15,000 participants who share new and significant discoveries in the cancer field. Specialty meetings, held throughout the year, focus on the latest developments in all areas of cancer research.