Link Between Diet and Breast Cancer Recurrence Risk Still Unknown

Aashini Master, DO

The Women’s Intervention Nutrition Study (WINS) and Women’s Healthy Eating and Living (WHEL) trials spearheaded healthy eating efforts in women who had been diagnosed with breast cancer, but physicians are still awaiting further data to see whether dietary fat reduction will confirm a benefit in recurrence risk, said Aashini Master, DO.

The WIN trial randomized women with resected, early-stage breast cancer to dietary intervention (n = 975) or control (n = 1462). The intervention arm received a lower fat intake and reflected a 6-pound less average weight loss than in the control arm. A median follow-up analysis of 60 months showed a 9.8% and 12.4% occurrence in relapse events in the intervention and control arms, respectively.¹

The WHEL trial examined a diet high in vegetables, fruit, and fiber, and low in dietary fat, but showed no reduction in breast cancer recurrence at a 7.3-year follow-up. The trial randomized women to a telephone counseling program, supplementary cooking classes, and newsletters that advised 5 daily servings of vegetables, 16 ounces of vegetable juice, 3 fruit servings, 30 grams of fiber, and 15% to 20% of fat intake (n = 1537) versus an advisory 5 A Day regimen (n = 1551). At follow-up, 16.7% of women in the intervention group versus 16.9% of women in the comparison group had a breast cancer event.²

“A lot of our patients who are faced with this diagnosis experience a lost sense of control,” explained Master. “Being a partner in their treatment gives them something to look forward to. It absolutely helps to empower them which is very important when they're going through something like this.”

Moreover, the PREDIMED study randomized women between the ages of 60 and 80 with a high risk of cardiovascular disease to a Mediterranean diet. At a median follow-up of 4.8 years, there were 35 confirmed cases of breast cancer. These rates, reported per 1000 person-years, were 1.1, 1.8, and 2.9 in the Mediterranean diet with extra-virgin olive oil arm, Mediterranean diet with nuts arm, and advisory diet arm, respectively.³ Master noted that additional studies are working to dispel purported benefits that claim to reduce the risk of diagnosis and recurrence.

OncLive: Please provide an overview of your presentation.

Can you elaborate on those studies?

In an interview during the 2018 OncLive^® State of the Science Summit™ on Breast Cancer, Master, assistant clinical professor, Division of Hematology/Oncology, University of California, Los Angeles Medical Center, discussed these intriguing studies and efforts to integrate nutrition and health into breast cancer survivorship.Master: We discussed the link between lifestyle factors, primarily obesity and nutrition, in the development of breast cancer—as well as the risk of recurrent breast cancer in those patients who have been diagnosed. A lot of the data have been based on observational studies or preclinical evidence. There are a few prospective randomized trials that we are going to review, as well as ongoing trials that we are awaiting the results for. The 2 main studies looking at women who have had lifestyle modifications following their diagnosis are the WINS and WHEL trials. Both trials were run in parallel, though the data were published 1 year apart. The WINS trial showed a benefit in women who reduced their fat intake by approximately 20%. Women, on average, had about a 6-pound weight loss and decreased their risk of breast cancer recurrence.

What percentage of patients need a significant alteration to their diet?

Is there anything beyond fat intake that is linked to risk of recurrence?

In the WHEL trial, the women who were in the intervention group didn’t demonstrate a weight loss. A 7.3-year follow-up did not demonstrate any benefit in recurrence-free survival (RFS). We're awaiting randomized trials to see if dietary fat reduction will lead to a benefit in recurrence risk. On average, when you look at obesity rates in the United States, it has become quite an epidemic. Every state has more than 20% of adults who are obese; 5 states have more than 35% of adults who are obese. It's not just obesity. Women with a body mass index in the overweight category have been shown to have an increased incidence of breast cancer. If I had to estimate in my practice, at least half of my patients could afford some weight loss. One thing that has been looked at is a Mediterranean diet. A Mediterranean diet is high is vegetables and fruits, animal protein mainly in the source of fish, as well as good fats such as nuts and whole grains. The Mediterranean diet is low in meats. Red meat and processed meat is a big component of a typical Western diet.

Are any other studies linked to breast cancer recurrence?

Is there anything else you would like to emphasize?

The data are suggestive that those who follow a Mediterranean diet have a decreased risk of breast cancer incidence or risk of developing breast cancer. The other thing we found is physical activity. Even in women who are not overweight, we found that physical activity still benefits them. Though the benefit is not as great as in women who are overweight or obese, there still is a benefit when we're discussing RFS. The Women's Health Initiative (WHI) is one of the biggest. It has been going on for over 30 years now. At the 2017 San Antonio Breast Cancer Symposium, Dr Rowan T Chlebowski presented a weight loss intervention within the WHI [that] showed a pretty outstanding benefit in decreasing recurrence rates. A lot of our patients are coming in and asking about supplements. When you do a quick Google search about supplements…there is some blog or some website claiming that a supplement is going to kill your cancer, reduce your risk, or whatever it may be. While there are some data for some of these supplements, most of it is preclinical.

However, it is exciting to consider. I’m hopeful and looking forward to running some clinical trials looking at certain supplements. For some of them, there's little downside, but for others I caution my patients. It's important for us as providers to have awareness regarding which ones are safe to utilize during active therapy and which ones we should potentially hold off on until patients have completed therapy.

References

1. Chlebowski R, Blackburn G, Thomson C, et al. Dietary fat reduction and breast cancer outcome; interim efficacy results from the Women’s Intervention Nutrition Study. J Natl Cancer Inst. 2006;98(24):1767-1776. doi: 10.1093/jnci/djj494.
2. Pierce J, Natarajan L, Caan B, et al. Influence of a diet very high in vegetables, fruit, and fiber and low in fat on prognosis following treatment for breast cancer. JAMA. 2007;298(3):289-298. doi: 10.1001/jama.298.3.289.
3. Toledo E, Salas-Salvadó J, Donat-Vargas C, et al. Mediterranean diet and invasive breast cancer risk among women at high cardiovascular risk in the PREDIMED trial: a randomized clinical trial. JAMA Intern Med. 2015;175(11):1752-1760. doi:10.1001/jamainternmed.2015.4838.