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October 18, 2023 | 8 minute read

Diet and Physical Activity: Making Strides Against Breast Cancer

Key Takeaways:

  • A lifestyle intervention during breast cancer chemotherapy more than doubled the rate of pathological complete response to neoadjuvant (pre-surgery) chemotherapy, an important predictor of long-term treatment success.
  • In this new study, counseling by oncology specialist dietitians enabled women going through breast cancer treatment to develop diet and physical activity habits closely aligned with AICR’s Cancer Prevention Recommendations.
  • It is important for health professionals, people with cancer and their families to recognize that this intervention did not involve extreme changes, but simply helped people more closely follow a healthy lifestyle.

A new study provides an optimistic look at how research is making strides against breast cancer through harnessing diet and physical activity. The power of these lifestyle choices to amplify the effectiveness of breast cancer treatment is a positive message during Breast Cancer Awareness Month.

The Lifestyle, Exercise, and Nutrition Early After Breast Cancer (LEANer) study is a randomized controlled trial that involved women newly diagnosed with stages I through III breast cancer (cancer had not yet spread to distant parts of the body).

All study participants received chemotherapy. Some received adjuvant chemotherapy (after surgery) and some received neoadjuvant chemotherapy (chemotherapy used to shrink cancer tumors before surgery). Half the women were randomly assigned to a nutrition and exercise intervention program. The other half were assigned to usual care and continued to receive the current standard of care, including access to a dietitian and survivorship clinics during treatment, upon referral by their oncologist.

Breast Cancer Research Study Explained

Researchers from Yale New Haven Hospital and the Dana-Farber Cancer Institute were looking at two different ways that nutrition and physical activity could potentially improve outcomes of chemotherapy.

  1. Completing full-dose chemotherapy as planned: In cancer treatment, a specific chemotherapy regimen is prescribed based on what is expected to be most effective for each person. But sometimes—usually because of treatment side effects—the dose or number of treatments needs to be reduced.

Reports estimate that, depending on the type of treatment regimen, nearly one in three women with breast cancer experience a reduction in treatment (calculated as relative dose intensity (RDI)). This is concerning, because when chemotherapy is reduced below 85 percent of what was initially prescribed, success of treatment is usually reduced.

Factors that can lead to reduced chemotherapy dose include:

  • Problems that make it difficult to eat well such as fatigue, nausea, decreased appetite and sores in the mouth or throat
  • Peripheral neuropathy—nerve damage in the feet, legs, arms or hands
  • Muscle loss, which can be worsened by cancer and its treatment

Nutrition strategies can provide adjustments to make it easier for people to get the calories and nutrients they need to maintain muscle. Research is currently investigating how physical activity, including resistance (strength-training) exercise, may help counter loss of muscle and reduce fatigue. Walking and resistance exercise may also help prevent or reduce chemotherapy-induced peripheral neuropathy, according to some studies.

  1. Pathological complete response to chemotherapy (PCR): For women who receive pre-surgery chemotherapy, a pathologist checks samples of tissue removed during surgery. If no invasive cancer cells are found, this is called pathological complete response and has been found to predict good long-term outcomes. Other terms for this are pathologic complete response and pathologic complete remission.

Changes in Diet and Physical Activity

The intervention components were based on successful diet and exercise strategies developed in previous studies with people at increased risk of diabetes and with cancer survivors, including the AICR-funded pilot LEAN study. The intervention incorporated results of research on behavior change and strategies to manage chemotherapy’s side effects. Registered dietitians who were board certified specialists in oncology nutrition provided these programs in about eight 30-minute counseling sessions spread over three months of chemotherapy.

Nutrition strategies in the intervention focused on a plant-forward diet, which was adapted in flavor, texture and nutrient content to meet individual needs and help manage blood sugars. Key goals included:

  • Vegetables and fruits: five servings or more each day
  • Dietary fiber: 25 grams of dietary fiber or more each day
  • Added sugars: no more than 30 grams a day
  • Red meat: no more than 18 ounces per week
  • Highly processed foods: limit consumption
  • Alcohol: no more than one standard alcoholic drink per day
A high-quality diet with increased fruits, vegetables, fiber and protein, and reduced added sugars may help preserve muscle tissue, lower levels of inflammation and support immune function, blood sugar and the gut microbiome.

Physical activity in the intervention was supported by counseling sessions and home-based exercise that included a progressive strength-training program. Key goals included:

  • Brisk walking of at least 150 minutes of moderate or at least 75 minutes of vigorous physical activity each week
  • Strength-training exercise at least two days each week
  • Reduced sedentary time

At the end of the study, participants who had been assigned to usual care were offered an individualized counseling session with a dietitian and a copy of the intervention materials.

Diet and Physical Activity Improved Even During Chemotherapy

Diet: Participants in this study started with an overall healthier diet than average U.S. adults of the same age. The Healthy Eating Index includes 13 components that give a diet quality score ranging from 0 to 100. Women in this study began with an average of about 67, better than the overall U.S. adult average score of 57.

Still, there was room for improvement, since their diets did not provide the recommended amounts of vegetables and fruits and totaled about 18–19 grams of dietary fiber (not unusual, but well below AICR’s Recommendation for at least 30 grams a day).

As part of the study, women who received nutrition counseling tended to increase vegetable and fruit consumption and fiber intake compared to women in the control group.

Physical activity: Likewise, at the start of the study, women in this study averaged less than a half-hour per week of moderate to vigorous physical activity. That’s substantially below the Recommendation for overall health that calls for at least 150 minutes a week of moderate activity, equivalent to a brisk walk. Few participated in resistance exercise.

Women assigned to usual care in this study increased moderate to vigorous physical activity somewhat, but resistance exercise remained almost the same. In contrast, women who received counseling and goals to increase physical activity made remarkable changes. Many were still not reaching recommended amounts of moderate to vigorous activity. But on average, they added more than two additional hours a week to their total, and the majority did add  resistance exercise.

Results of the Breast Cancer Research

The LEANer trial produced three key conclusions:

Chemotherapy need not be a barrier to making improvements in physical activity and diet quality, an important finding in itself, explains Maura Harrigan, MS, RDN, CSO. She is Project Manager of the LEANer Study at the Yale School of Public Health and Yale Cancer Center.

Harrigan says, “We were able to show that women were able to improve their diet quality and increase their physical activity during chemotherapy despite their side-effects. Counseling from the registered dietitians who were board certified specialists in oncology nutrition focused on managing the side effects of chemotherapy and encouraging the restorative power of walking.”

Physiological complete response to neoadjuvant (pre-surgery) chemotherapy was much more likely—achieved by 53 percent of women—in the intervention group compared to 28 percent in the group receiving usual care. Among the different types of breast cancer, PCR improved with the intervention for women with hormone receptor-positive/HER2-negative and triple-negative breast cancers.

“This finding provides an exciting new possibility that diet and exercise can influence chemotherapy outcomes through factors other than just how much chemotherapy was completed,” says Harrigan. This could include benefits for immune, inflammatory and metabolic pathways, for example. “Further explanation is needed since it wasn’t the primary outcome of our study and needs to be confirmed with larger trials.”

Completing full dose of chemotherapy, evaluated as RDI, was equally high among women in the lifestyle intervention and in the usual care group. There was no difference between the groups in how many reached the goal of receiving at least 85 percent of the intended treatment dose.

Researchers conducting the study suggest that diet and physical activity might have more influence on whether people are able to receive full chemotherapy as intended in population groups that have lower rates of chemotherapy completion.

What’s Ahead for Making Strides Against Breast Cancer

This is the first study to show the direct impact on an important predictor of treatment outcome from multi-dimensional diet and physical activity strategies introduced during cancer treatment. Once these results are confirmed, scientists can evaluate how strategies can be tweaked and how people with different types of cancer and treatment can be supported by them.

Harrigan concludes “we recruited women who were inactive and not meeting nutrition goals. The results prove that women are willing and able to develop healthier eating and exercise habits during treatment for breast cancer, even if they didn’t have them before. It’s never too late to start.”

This provides a positive note for Breast Cancer Awareness Month while we await further research. Changes in diet and physical activity were not extreme and did not call for severe restrictions or avoidance of any food group. The messages that helped these women are exactly what you can find in the AICR Cancer Prevention Recommendations and the New American Plate model for healthy eating.

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