What effects do physical activity (PA) interventions have on women with breast cancer who have completed cancer treatment?
After receiving breast cancer treatment, women may experience adverse mental and physical events caused by the cancer and by its treatment. These adverse events can result in a shorter life after treatment and can have a negative impact on quality of life (QoL) and on physical and mental health. Some studies suggest that being regularly physically active after treatment might lower the chance that breast cancer may come back, or that women may die of breast cancer. Regular PA may lead to a wide range of other beneficial effects, including improved QoL, mental health, and physical function. We wanted to determine whether PA has an effect on risk of recurrence and dying from breast cancer, QoL, and other aspects of well-being in women who had breast cancer after treatment.
We included only studies consisting of women with breast cancer who had completed active cancer treatment. These studies compared outcomes of women involved in PA interventions versus outcomes of those who were offered usual care or no PA. Participants must have been assigned to a group in random or somewhat random fashion. The evidence is current to September 2015.
This review includes 63 trials involving 5761 participants. Most trials (28) consisted of aerobic exercise (e.g. walking, cycling, dance), whereas seven trials included a resistance training-only group, and 21 trials included a combined aerobic exercise and resistance training group. One in five participants placed in a PA intervention group dropped out before the end of the study, and on average one-quarter of target PA sessions were missed by participants. We found no studies that looked at effects of PA after cancer treatment on risk of recurrence or dying from breast cancer or any other cause. We found that participants performing PA had more favourable values by the end of the intervention and experienced greater positive changes over the intervention period in terms of QoL, views on their emotional health and physical ability, social function, feelings of worry, stamina, PA levels, body fat, and strength of muscles, compared with usual care participants. Researchers found no effects on perceived health, ability to sleep, feelings of pain, sexual function, body mass index, waist-to-hip girth ratio, and bone health of the upper and lower spine or hip. At least three months after completion of the intervention, actual values and changes from the start of the intervention in feelings of tiredness, stamina, and self-reported PA levels remained more favourable in participants given PA intervention than in those given usual care. Both aerobic exercise only and combined aerobic and resistance training interventions improved QoL and stamina. Aerobic exercise improved views on perceived emotional health and physical ability, as well as social function and self-reported PA levels, whereas resistance training resulted in greater improvement in muscle strength. Combined aerobic and resistance training interventions led to reduced feelings of tiredness. Trialists reported few minor adverse events among those given PA interventions.
Quality of the evidence
We rated the quality of evidence related to various aspects of health as very low, low, or moderate. We noted wide variation among the interventions that we looked at in terms of types of PA, frequency of sessions per week, levels of effort among participants, and session and intervention duration. Also, researchers measured aspects of health in many different ways. Other problems with eligible studies included lack of information on how study authors placed participants in groups at random, whether researchers who were carrying out the tests knew which group the person being tested belonged to, and how researchers dealt with data missing from their studies. In many aspects, we could not rule out the chance that positive effects observed were small enough that they were not important. It is also possible that smaller studies that have not found favourable effects of PA in women with breast cancer after treatment have not been published, because study authors often find it difficult to publish studies that have not found beneficial effects.