Regular exercise or physical activity has widely been reported to reduce breast cancer risk and recurrence. The chemopreventive effect appears to be greater for premenopausal women. Now a new study has found that hormone receptor negative (ER-/PR-) disease is most responsive to exercise.
Exercise directly impacts breast cancer
Regular exercise or physical activity commonly is thought to reduce breast cancer risk through its beneficial influence on circulating sex hormones, insulin sensitivity, inflammation, and weight control. However, exercise also has more direct effects on breast tumors.
For example, aerobic exercise has been demonstrated to decrease tumor hypoxia, a low-oxygen condition under which solid breast tumors can thrive. In addition, exercise induces metabolic reprogramming of internal organs, which appears to help prevent metastatic colonization by limiting the nutrients available to tumors. Exercise also has been reported to improve cancer immunosurveillance by stimulating various immune cell subtypes to infiltrate tumors. Finally, increasing physical activity after diagnosis has been shown to affect regulation of tumor suppressor genes in ways favorable to survival.
Latest research finds response to exercise varies
The study referenced above was designed to investigate the link between level of exercise (as measured after diagnosis but before treatment) and risk of breast cancer recurrence. To conduct the study, the authors analyzed prospective data concerning 10,359 women with stage I-III primary breast cancer who enrolled in the French CANcer TOxicities (CANTO) study between 2012 and 2018. Study participants were followed through October 2021, with median follow-up of 5.4 years.
Level of exercise was determined using the Global Physical Activity Questionnaire-16 (quantified in standardized metabolic equivalent hours per week: MET-h/wk). The authors assessed the dose/exposure response of pretreatment exercise on distant recurrence-free interval for all study participants. These results were further analyzed according to hormonal subtype and menopausal status.
The relationship between exercise and distant recurrence-free interval was found to be nonlinear for study participants overall. Exercising 5 MET-h/wk to approximately 25 MET-h/wk was associated with a proportionate reduction in distant recurrence. However, exercising more than 25 MET-h/wk did not result in any additional reduction. Based on this finding, exercise was collapsed into two categories (1) "no exercise" (0 to <5 MET-h/wk) and (2) "exercise" (≥ 5 MET-h/wk). Women in the exercise group were found to have an 18% lower five-year risk of breast cancer recurrence than those in the no exercise group.
Analysis by subtype demonstrated that women with hormone receptor negative (ER-/PR-/HER2+ or triple negative (ER-/PR-/HER2-)) disease were most responsive to exercise. Those with ER+/PR+/HER2- tumors also saw some benefit whereas no significant relationship between exercise and distant recurrence-free interval was found for triple positive (ER+/PR+/HER2+) disease. Premenopausal women benefited more from exercise than postmenopausal participants.
The authors conclude that postdiagnosis/pretreatment exercise level is associated with lower risk of distant recurrence in a nonlinear fashion, In addition, the impact of exercise on recurrence varies according to breast cancer subtype and menopausal status.