Women with healthier diets before an ovarian cancer diagnosis are less likely to die in the years following the cancer than women with poorer diet, according to a new study published in the Journal of the National Cancer Institute.
Ovarian cancer is the fifth leading cause of cancer deaths among women in the US, affecting an estimated 1 in 73 women during their lifetime. The disease, which starts in the two ovaries that are located in the uterus, typically causes few or no symptoms in the beginning, making it particularly difficult to diagnose and treat. The American Cancer Society estimates that in 2014, about 21,980 new cases of ovarian cancer will be diagnosed and 14,270 American women will die of it.
Survival rates for ovarian cancer are affected by a number of factors including general health status, tumor stage, treatment type(s), and treatment response. However, the influence of diet–a modifiable lifestyle factor and potential prognostic factor–on survival after an ovarian cancer diagnosis remains unclear.
To evaluate diet quality and the overall influence of diet on ovarian cancer survival, Dr. Cynthia A. Thomson, Ph.D., R.D., a professor from the Mel & Enid Zuckerman College of Public Health and University of Arizona Cancer Center researcher, and colleagues analyzed data from the Women’s Health Initiative Study, a long-term national health study focused preventing heart disease, cancer, and osteoporotic fractures in postmenopausal women.
The researchers looked at 636 cases of ovarian cancer among postmenopausal women occurring between 1993 and 1998, 90 percent of which were invasive cancers. Participants’ dietary intake was assessed using food frequency questionnaires and estimates of overall diet quality were measured using the Healthy Eating Index-2005. Researchers also 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.
Healthy diet associated with 27% reduced risk of mortality
As of September 17, 2012, 354 of the women had died, and 305 of those died specifically from ovarian cancer, the study found. When the researchers divided the women into three groups based on their diet quality, those in the healthiest-eating group were 27 percent less likely to die of any cause after ovarian cancer diagnosis than those in the poorest diet group.
There was a similar but slightly weaker association between pre-diagnosis diet and death due specifically to ovarian cancer. Interestingly, individual dietary components were not associated with mortality after ovarian cancer, suggesting it is the composite of healthy dietary choices that impacts survival.
Subgroup analyses revealed that women with a history of diabetes and those with a waist circumference greater than 34 inches may not get the same survival benefit from a healthy diet as other women. The study authors note that past research has already linked diabetes with higher-than-average mortality in ovarian cancer, which could explain the lack of survival benefits.
The amount of regular exercise women got before diagnosis did not seem to affect the link between diet quality and survival, the team found. 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, they add.
Offering a potential explanation of the observed link between diet and survival, the authors note that a healthy diet before diagnosis may indicate a stronger immune system and, indirectly, the capacity to respond favorably to cancer therapy.
Past studies have also shown that diets rich in fruits, vegetables and whole grains may lower inflammation, which has been linked to ovarian cancer mortality, the article says. “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,” Dr. Thomson adds.
In any case, Dr. Thomson says, maintaining a healthy diet is an important modifiable factor associated with reduced overall cancer risk and improved survival rates after cancer. “One in two U.S. 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.”