Exercise may cut breast cancer risk

A study conducted among Vietnamese women found that engaging in regular exercise leads to a reduction in the overall risk of breast cancer, especially the HER2-enriched subtype.

In this study, regular exercise was inversely associated with the risk of breast cancer (adjusted odds ratio [OR], 0.66, 95 percent confidence interval, 0.49–0.90), with a stronger association among women with HER2-enriched disease (adjusted OR, 0.55, 95 percent CI, 0.33–0.91).

No significant associations were observed between regular exercise and other breast cancer subtypes. [Tran, D, et al, WCC 2024]

Limited, inconsistent data

Physical activity is associated with reduced breast cancer mortality and recurrence and fewer or less severe adverse effects following treatment. [J Natl Cancer Inst 2021;113:54-63; Cancer Nurs 2018;41:E31-E38; Epidemiol Rev 2017;39:71-92] However, following a diagnosis of breast cancer, women tend to cut their physical activity levels, especially those who are undergoing treatment, compared with untreated patients. [Cancer 2003;97:1746-1757]

Given its importance in improving physiological processes, the role of exercise after breast cancer therapy has become an important area of research. [Med Sci Sport Exerc 2010;42:1409-1426]

“[However,] evidence of associations between physical activity and the risk of breast cancer is limited and inconsistent. [Hence,] we evaluated associations of physical activity with the risk of breast cancer overall and by molecular subtypes,” noted study first author Dung Tran from the Vietnam K Hospital, Hanoi, Vietnam, and colleagues, in their presentation at WCC 2024.

The investigators utilized data from the case-control Vietnamese Breast Cancer Study. They evaluated 492 women with breast cancer (mean age 50.1 years) and 468 age-matched healthy women (mean age 49.9 years). The breast cancer cases were from the Vietnam National Cancer Hospital and Hanoi Oncology Hospital. The control participants were recruited either from the community or from women related to non-breast cancer patients; they were then frequency-matched to the case on age.

The women were instructed to provide information about exercise participation and daily activities during the 10 years prior to their enrolment in the study. Each activity was assigned a standard metabolic equivalent (MET) score, and physical activity in MET hours per week was calculated.

Breast cancer cases were categorized into four major molecular subtypes: luminal A, luminal B, HER2-enriched, and triple-negative/basal-like subtypes.

Regular exercise and physical activity associations with breast cancer were assessed via multivariate unconditional logistic regression for overall and molecular subtypes with adjustments for related factors, such as age at diagnosis, educational level, annual house income, residence, family history of cancer (first-degree), number of children, menopausal status, BMI level, regular exercise, daily walking, daily physical activity, and total physical activity.

Nearly 50 percent (45.6 percent) of the women with breast cancer had the luminal B subtype. The next most common subtype of breast cancer was HER2-enriched (23.3 percent), followed by luminal A (16.2 percent) and triple-negative/basal-like (10.2 percent).

Compared with the healthy participants, women who had breast cancer had less regular exercise and daily walking (p<0.05). Conversely, there were no significant associations observed between breast cancer risk (overall and by molecular subtypes) and total physical activity and daily physical activities.

Further research is warranted to explore biomarkers related to breast cancer risk and how physical activity affects these biomarkers. Moreover, studies on exercise are recommended to ascertain the specific types of exercise, as well as dosing and timing of activity, that contribute to the decline in breast cancer risk. [Recent Results Cancer Res 2011:186:13-42]