NEW YORK - Women with healthier diets before an ovarian cancer diagnosis are less likely to die in the years following the cancer than women with poorer diets, according to a new study.
The exceptions were women with diabetes or a high waist circumference, which is often linked to diabetes.
A healthy diet before diagnosis may indicate a stronger immune system and, indirectly, the capacity to respond favourably to cancer therapy, said lead author Cynthia A. Thomson of Health Promotion Sciences at the Canyon Ranch Center for Prevention and Health Promotion at the University of Arizona in Tucson.
"It also may reflect our capacity to sustain healthy eating after diagnosis, which in turn could support better health in a broader sense," Thomson told Reuters Health by email.
Researchers looked back at 636 cases of ovarian cancer occurring between 1993 and 1998, 90 per cent of which were invasive cancers.
The women had filled out dietary and physical activity questionnaires at least one year before their cancer diagnoses as part of the larger Women's Health Initiative study. Researchers measured their heights, weights and waist circumferences.
The healthy eating index in this study measured 10 dietary components, scoring diets with a higher amount of vegetables and fruit, more variety in vegetables and fruit, more whole grains, lower amounts of fat and alcohol and more fiber as healthier than other diets.
On average, the women were diagnosed with ovarian cancer around age 63.
As of September 17, 2012, 354 of the women had died, and 305 of those died specifically from ovarian cancer.
When the researchers divided the women into three groups based on their diet quality, those in the healthiest-eating group were 27 per cent less likely to die of any cause after ovarian cancer diagnosis than those in the poorest diet group, according to the results published in JNCI, the Journal of the National Cancer Institute.
There was a similar but slightly weaker association between pre-diagnosis diet and death due specifically to ovarian cancer.
"The index gives more points for eating good foods, such as vegetables and whole grains, and fewer points for eating not-recommended foods, such as added sugars, fatty foods and refined grains," said Dr. Elisa V. Bandera, associate professor of Epidemiology at Rutgers Cancer Institute of New Jersey in New Brunswick.
"Interestingly, they found that it was not the individual components that affected mortality, but an overall healthy diet," said Bandera, who was not part of the new study.
A diet rich in fruits, vegetables and whole grains may lower inflammation, which has been linked to ovarian cancer mortality, she told Reuters Heath by email.
"Such a diet has also been linked to reduced risk of other chronic diseases such as diabetes and cardiovascular disease which may complicate ovarian cancer treatment and increase mortality," she said.
High scores on the Healthy Eating Index are very similar to guidelines and recommendations for cancer survivors provided by the American Institute for Cancer Research and the American Cancer Society, Dr. Anne McTiernan of the Fred Hutchinson Cancer Research Center in Seattle told Reuters Health by email.
"However, the data on diet and lifestyle associations with ovarian cancer survival are all observational," said McTiernan, who was not involved in the new study. "Clear recommendations would require a randomized controlled clinical trial - the gold standard of medical evidence - before women with ovarian cancer could be advised to change their lifestyles in order to improve their prognosis."
Women with a history of diabetes and those with a waist circumference greater than 34 inches did not seem to get the same survival benefit from a healthy diet as other women. In their report, the study authors note that past research has already linked diabetes with higher-than-average mortality in ovarian cancer.
The amount of regular exercise women got before diagnosis did not seem to affect the link between diet quality and survival.
Although the researchers accounted for exercise and total calorie intake, they did not account for ovarian cancer treatment. Women who had healthier diets may also have had access to better treatment, Bandera noted.
In any case, Thomson said, healthy diets do seem to be important to reduce cancer risk and to improve survival after cancer. "One in two US adults will be diagnosed with some form of cancer in their lifetime and eating healthy is important in regards to how we come through this experience."
Healthy behaviours may also delay the onset of cancer, for example from age 55 to 65, but that is difficult to demonstrate, she said.