Exercise as it relates to Disease/The role of physical activity in the survival of diagnosed breast cancer patients

What is the background to this research?

Breast cancer is the most common cancer affecting women however some men are also affected. With over 2 million new cases been diagnosed in 2018 alone , breast cancer has a chronic impact on women across the globe. Literature suggests common risk factors for breast cancer include age, obesity, level of physical activity and circulating levels of sex hormones i.e. oestrogen . However, there is little research showing the effect that physical activity plays in the prevention and treatment of breast cancer , despite its positive impact in managing other chronic diseases.

Where is the research from?

This research comes from the 1976 Nurses’ Health Study (NHS) where data looked at 2987 female registered nurses who had been diagnosed with breast cancer in either stages I, II or III . With the prevalence of the condition affecting women globally, this article published by the American Medical Association provides relevant information to many women.

What kind of research was this?

This study is a prospective observational study as it deals with observing characteristics of a population such as the diagnosed breast cancer cohort over a period of 16 years . Observational studies are frequently used in medical research however often result in biased studies, particularly as surveying often involves self-reporting.

What did the research involve?

Measurement of breast cancer and mortality

Self-reported diagnosis were supported by professional health records which were then used to quantify participants in this study. By mailing questionnaires to diagnosed breast cancer sufferers, the participants are able to identify their condition and be subject to participate in the study. Additionally, confirmation from family members and research in the National Death Index are the two methods used in order to account for those participants who passed away throughout the course of the study.

Exclusions

It is important to place the patients’ health as a priority during a study especially because it involves both cancer and physical activity. Situations in which diagnosed patients were deemed unable to participate in the study include:

• Previously diagnosed with breast or any other cancer (other than non-melanoma) prior to 1984.
• Had been diagnosed with stage IV of the cancer or stage wasn’t provided
• Provided no report of physical activity following diagnosis
• Unable to walk
• Had 4 or more positive nodes

From this there may be a misconception of the result ‘physical activity increases survival of breast cancer’ to show that physical activity reduces the risk of mortality in all sufferers, when in fact it may only be true in only 67% of diagnosed patients or those who meet the criteria.

Assessment of physical activity exposure

The standard measure of exercise duration and intensity is through the use of metabolic equivalent (MET) hours per week. The study split participants into the following groups in order to analyse results;

• < 3
• 3 – 8.9
• 9 – 14.9
• 15 – 23.9
• > 24

Activity levels were first assessed two years following diagnosis in all patients so that treatment could first be provided without interference, further enhancing the safety of the study. In order to reduce the subjectivity of data collected, participants were provided with a general guide was provided showing (walking = 3 METS); (jogging = 7 METs) and (running = 12 METs). This guide was provided along with a list of common activities in order to normalise the results provided as best as possible so that personal interpretation didn’t alter the results provided.

What were the basic results?

Physical activity is shown to provide breast cancer sufferers with significant benefits of reducing the risk of adverse effects associated with breast cancer such as recurrence and mortality . Lifestyle factors play an important role in the amount of physical activity completed by an individuals including amounts prior to diagnosis. The study shows that the women who participated in 9 – 14.9 MET hours per week (equivalent of walking for 3-5 hours) were the women who experienced most benefit from physical activity . Contrastingly, activity that exceeded this amount may not provide any additional benefit in terms of outcome for the patient, where often higher amounts would result in poor health consequences. This suggests that cancer-related fatigue has a significant impact on sufferers as a greater physiological demand is placed on the body, leading to sleep disturbances, stress and further decreased immune function . Therefore, excess in physical activity is shown to have reduced benefit when compared to those participating in 9 – 14.9 MET hours per week.

The data collected provides a subjective measure of physical activity due to the self-reported nature of the study which has been noted by Holmes . By asking people to indicate the duration and intensity there will be discrepancies due to interpretation, particularly regarding intensity. However, this impact has been reduced by indicating how many METs an activity is, as a guide walking to equal 3 METs.

What conclusions can we take from this research?

This study was able to illustrate that physical activity plays a positive role in reducing mortality and recurrence associated with breast cancer. External literature supports the elements mentioned in the text, particularly those associated with obesity, sex hormones and the risk associated with women post-menopause . Inversely, women who are not physically active following breast cancer diagnosis are exposed to an increase mortality risk . This further supports the role of physical activity in reducing recurrence and mortality rates. Due to the evidence being well supported in literature, the study provides accurate data whereby both intensity and duration of physical activity are shown to benefit breast cancer sufferers.

Practical advice

Early detection is vital to reduce mortality associated with breast cancer . Women over the age of 40 are encouraged to get a free mammogram every 2 years to promote early detection, this can be done through BreastScreen Australia.

Prevention is often the best cure for chronic diseases such as breast cancer. By being physically active you are able to prevent risks associated with a broad range of chronic diseases such as diabetes, hypertension and cancer. Completing regular physical activity later in life is an effective method of reducing the risk of high levels of sex hormones resulting in risk of breast cancer.

If you have any concerns or questions do not hesitate to contact your general practitioner or call a support line at Breast Cancer Network Australia. Additionally if you would like further information or would like to assist in fighting against breast cancer, the McGrath Foundation work in funding for more breast care nurses.

Further resources

BreastScreen Australia - http://www.cancerscreening.gov.au/internet/screening/publishing.nsf/Content/breast-screening-1

Breast Cancer Network Australia - https://www.bcna.org.au/understanding-breast-cancer/bcna-helpline/

McGrath Foundation - https://www.mcgrathfoundation.com.au/Default.aspx