Very few studies have looked at the impact of diet or exercise in patients with advanced breast cancer (ABC). On a biological level, repeated exercise may limit tumour growth, and some dietary interventions, e.g., plant-based diets, can help improve fatigue. But more research is needed in all these areas. Until there is more evidence, there are things that patients can do to improve their quality of life with a diagnosis of advanced breast cancer. Avoid sitting still – and if you can, aim for 150 minutes per week of moderate exercise (that’s a half hour walk 5 days a week). Even seated exercises help. The usual recommendations relating to increasing plant-based foods and reducing red/processed meats and sugar apply. Healthcare systems can also overcome the burdens to diet and exercise interventions by improving referral systems, including access to dietitians and exercise specialists, and by providing specific lifestyle prescriptions (like the Green Prescription here in NZ).
Here's BCAC’s report of a talk on this topic at the recent ABC7 international advanced breast cancer conference:
Relationship between diet and exercise in advanced breast cancer – the jury is still out
Dr Leonor Vasconcelos de Matos, Champalimaud Foundation, Lisbon, Portugal.
The discussion about diet and exercise in advanced breast cancer (ABC) is usually started by patients themselves – because this is one of the few areas of the disease where patients can regain some control. However, most evidence-based recommendations on diet and exercise are about prevention or reducing recurrence. And while there is growing acknowledgement that exercise benefits ABC by reducing symptoms, especially fatigue, people with ABC are still often excluded from lifestyle intervention trials because it is deemed unsafe or a burden, and it is assumed it won’t have any effect on the disease.
Exercise improves quality of life in ABC – but still no evidence of clinical effect on survival
At a cellular level and in animal studies, repeated exercise reduces tumour cell growth rate, activates the immune system, and increases production of substances that have anti-tumour effects. Regular exercise reduces chronic systemic inflammation and can enhance the actions of some drugs such as tamoxifen and chemotherapy, to reduce tumour growth. However, this biology has not yet been shown to translate to increased survival clinically in ABC. Higher levels of physical activity are associated with lower breast cancer mortality but this has not been shown in active disease. So although the mechanisms of exercise and survival make sense, more research is needed to find out if exercises increases survival in ABC.
Quality of life is clearer. Exercise improves fatigue, sleep quality, and sense of empowerment, and reduces anxiety, depression and lymphoedema. A randomised controlled trial showed that seated exercise therapy during chemotherapy resulted in a slower decline in quality of life [1] while a supervised resistance training program in patients with bone metastases resulted in improved strength and functional ability, better quality of life and increased social function [2].
Diet in ABC – a ‘data-free zone’
There are no controlled trials on diet and ABC. If we look at the biology, plant-based diets may potentially inhibit tumour growth, and calorie-controlled diets may do the same. However, this is not an option for patients facing cachexia (loss of muscle or fat mass) or sarcopenia (loss of muscle strength). Avoiding sugars may reduce local and systemic inflammation and there are hints a ketogenic diet may be beneficial. However, again, this is not being studied in cancer patients but only in cancer cells.
In the clinic, only one meta-analysis has looked at the effect of diet on cancer control and quality of life. It found a small potential pattern of an effect of a positive effect of a plant-based diet on fatigue [3].
There is therefore insufficient evidence to recommend any type of diet or fasting to improve quality of life or cancer control. With our current knowledge, there is also no evidence to recommend for or against weight loss or prevention of weight gain.
Recommendations: more plant-based foods and more exercise programmes
So what can patients do? The recommendations are what one might expect [4].
In terms of diet, the World Cancer Research Fund recommends:
• MORE plant-based foods
• MORE nutritional consultations
• MORE support to manage anaemia, diarrhoea, nausea and vomiting, which all contribute to cancer-related fatigue.
• LESS red and processed meats, energy-dense foods, salt, sugary drinks and alcohol. Don’t rely on dietary supplements.
For exercise, there are more specific recommendations:
• Avoid inactivity
• Aim for 150 minutes of moderate aerobic activity OR 75 minutes of vigorous exercise per week (tailored to individual patients and in consultation with your oncologist).
Despite over 100 clinical trials being done on exercise in cancer patients, including fragile patients, demonstrating its safety, exercise plays a ‘surprisingly limited role in clinical oncology at present’.
Barriers and solutions to exercise programmes in ABC
Barriers:
• Lack of financial support/insurance coverage
• Lack of structure/workforce, e.g., trained dietitians and exercise physiologists
• Lack of triage systems and referral pathways
• Need for motivation from patients
• Fears from health professionals about patient safety.
Solutions:
• Promote research
• Improve awareness of benefits with patient education
• Enhance enjoyment of activities
• Provide specific exercise/diet prescriptions
• Set goals
• Self-monitor behaviour, including eHealth apps and wearables
• Provide social support
Providing social support for exercise programmes is possibly the most important thing that can be done, even though its benefit cannot always be measured quantitatively.
References
1. Headley JA, et al. Oncol Nurs Forum. 2004 Sep 17;31(5):977-83. doi: 10.1188/04.ONF.977-983
2. Cormie P et al. Support Care Cancer. 2014 Jun;22(6):1537-48. doi: 10.1007/s00520-013-2103-1
3. Baguley BJ, et al. Br J Nutr. 2019 Sep 14;122(5):527-541. Available at: doi: 10.1017/S000711451800363X.
4. World Cancer Research Fund. https://www.wcrf.org/diet-activity-and-cancer/cancer-prevention-recommendations/
Marion Barnett
29 November 2023
