Researchers at Harvard School of Public Health and Harvard Medical School said that successful surgery appeared 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.
The study, presented to the 96th Annual Meeting of the American Association for Cancer Research, showed that patients with high vitamin D intake - having 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.
However, the researchers added they could not yet explain the link between vitamin D and surgery outcome and needed to validate the study, though a number of other studies have hinted that vitamin D may work to inhibit various 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," said the lead investigator, Dr. Wei Zhou.
"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."
He cautioned that this research did not mean that patients should try and time their operations for a particular season, but if the results were validated, supplementation with vitamin D could be beneficial for survival.
The research team looked at disease free survival (DFS) and overall survival (OS) in 456 patients who had 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.
When the joint effects of surgery season and vitamin D intake were considered, the researchers found that 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.