It was estimated that cancer caused 9.6 million deaths in 2018, with breast cancer being the most common cancer among women, affecting 2.1 million women each year and causing the greatest number of cancer deaths. Although breast cancer incidence is higher among women in more developed regions, rates are increasing in almost every region of the world. Women diagnosed with stage I–III breast cancer undergo treatment, most often with a series of surgeries, postoperative chemotherapy, radiation therapy, and oral anti-estrogen drugs.

Following treatment, many of these women experience long-term physical and psychosocial sequelae of the cancer and its treatment, including pain, fatigue, lymphedema, psychological distress, anxiety, and depression. Feelings of sadness, hopelessness, and loss of sleep characterize depression, as well as changes in appetite, in addition to delayed psychomotor development, decreased quality of life (QOL), deterioration in social and occupational functioning.

Depressive mood is common in breast cancer survivors, with a prevalence of 1.5–46%. Factors that contribute to the development of depression in cancer survivors include poor psychological adaptation to certain symptoms (e.g., sexual, intestinal, fatigue), the severity of symptoms (e.g., pain, fatigue), or the treatment itself. In other cases, treatment causes hypothyroidism, electrolyte imbalances or anemia, which increases the risk of a depressive episode. Therefore, maintaining general health and surviving the cancer stage are as important as treatment. As a result, traditional approaches to monitoring cancer recurrence have expanded to include factors such as the overall management of women's health recovery, i.e., psychosocial and physical effects, promotion of healthy lifestyles. It is expected that health professionals from different fields of expertise (e.g., psychologists, physiotherapists, dietitians) will be involved in this process.

Although the data show the positive impact of healthy lifestyle and physical activity on reducing breast cancer mortality, the subsequent physical and psychological impact of exercise on breast cancer survivors is also extremely significant. In this study, my colleagues and I assessed the impact of post-diagnosis exercise on depression, physical functioning, and mortality in breast cancer survivors. This systematic review and meta-analysis examined 26 randomized controlled trials. Pooled statistics on depression, physical functioning, and mortality among breast cancer survivors were calculated using standardized mean differences (SMD).

This systematic review supports that exercise after diagnosis has a beneficial and positive effect on depression and survival in patients with breast cancer. An analysis of randomized controlled trials found statistically significant improvements in depression following an exercise intervention. Although the studies used a variety of exercise types, including aerobic, strength, resistance, core, yoga, walking, scapular exercises, cycling, tai chi, and calisthenics, the results show that aerobic and strength training, both alone and in a group, improved physical functioning and eliminated some symptoms in patients with breast cancer.

In terms of mortality rates, findings show that both moderate and moderate to vigorous exercise reduced breast cancer-related mortality. Overall, exercise after diagnosis resulted in a 37% reduction in breast cancer-related mortality. All-cause mortality was reduced by 39% when physical activity was included. All exercise levels demonstrated this beneficial effect. A summary of 26 studies in this study confirms that physical activity (exercise) is statistically significant in reducing the risk of all-cause mortality and breast cancer mortality. Factors associated with depression varied from study to study depending on its primary objectives. Therefore, an effective physical activity program may address the health consequences of cancer diagnosis and treatment.

Because individual responses to specific physical activity may vary due to cancer treatment on the physiological system, exercise tolerance, side effects of cancer treatment, or demographic factors (e.g., age), understanding these interactions is a topic of ongoing research, especially as new treatments become available. New studies are expected to examine the long-term effects of exercise on health and quality of life in breast cancer survivors, as most of the studies included in this meta-analysis had short follow-up periods. By recruiting all potential participants from different ethnic groups and with different demographics, and then counseling about the biological and psychological effects of exercise and healthy eating during and after breast cancer treatment, patients may experience reduced stress and depression, thereby changing their attitudes and behavior.