For Women with Breast Cancer, Regular Exercise May Improve Survival

, by NCI Staff

A new study adds to existing evidence linking physical activity with longer survival in women diagnosed with high-risk breast cancer.

Women who engaged in regular physical activity before their cancer diagnosis and after treatment were less likely to have their cancer come back (recur) or to die compared with those who were inactive, the study found.

The study was unusual in that it collected information on the physical activity levels of women with high-risk breast cancer (cancer that is likely to recur or spread) at multiple time points—shortly before their diagnosis, during chemotherapy, and after completion of treatment.

“Our data strongly suggest that the more consistently active patients were, the better they did,” said lead study author Rikki Cannioto, Ph.D., Ed.D., of Roswell Park Comprehensive Cancer Center in Buffalo, NY.

And while survival was extended in women who consistently met federal Physical Activity Guidelines for Americans over time compared with those who did not meet the guidelines, “there was still a survival advantage for women who [were active but] didn’t quite meet the guidelines,” Dr. Cannioto said.

These results “provide evidence that physical activity at any point in time appears to be beneficial for breast cancer survivors,” said Joanne Elena, Ph.D., M.P.H., of the Epidemiology and Genomics Research Program in NCI’s Division of Cancer Control and Population Sciences (DCCPS), who was not involved with the study.

“This study gives us further evidence that being more physically active after a diagnosis of breast cancer is one of the ways that breast cancer survivors can take matters into their hands and improve their health and decrease their likelihood of dying,” said Kathryn Schmitz, Ph.D., M.P.H., an exercise oncology researcher at the Penn State College of Medicine, who also was not involved with the study.

The new study was published April 2 in the Journal of the National Cancer Institute.

Looking at Exercise Over Time

The findings come from the NCI-funded Diet, Exercise, Lifestyle, and Cancer Prognosis (DELCaP) study, led by Christine Ambrosone, Ph.D., also of Roswell Park. The study was embedded in a large clinical trial, led by the NCI-funded SWOG Cancer Research Network, that compared different chemotherapy regimens for women with high-risk breast cancer.

The physical activity analysis by Dr. Cannioto and her colleagues included 1,340 patients from the SWOG trial who also enrolled in the DELCaP study. Participants completed questionnaires about the type, frequency, and duration of recreational physical activity they engaged in at four time points: during the month before diagnosis, during treatment, and at 1 and 2 years after study enrollment. Participants were followed for up to 15 years or until death, with a mean follow-up time of 89 months (7.4 years). 

Much, though not all, previous epidemiologic research describing the link between physical activity and cancer outcomes is based on physical activity data collected at only one time point, Dr. Cannioto said.

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Using the questionnaire responses, the researchers determined whether participants had met the minimum 2018 Physical Activity Guidelines for Americans at each time point. The guidelines recommend that adults engage in at least 2.5 to 5 hours of moderate-intensity physical activity or 1.25 to 2.5 hours of vigorous-intensity aerobic physical activity per week.

Women with breast cancer who met the minimum physical activity guidelines both before diagnosis and at the 2-year follow-up (after treatment) had a 55% reduced chance of their cancer returning and a 68% reduced chance of death from any cause (not just breast cancer) compared with those who did not meet the guidelines at both times.

Among patients who did not meet the guidelines before diagnosis but met them at the 2-year follow-up, the chance of recurrence or death was reduced by 46% and 43%, respectively, compared with those who did not meet the guidelines at both times. The finding, Dr. Elena said, suggests that “it’s never too late to start exercising to derive benefits.” 

The researchers also performed “time-dependent analyses,” which help to account for the fact that physical activity data was collected over multiple time points,” Dr. Cannioto explained.

These analyses showed that, compared with inactive patients, the likelihood of death from any cause was reduced the most among highly active patients, but even patients who regularly engaged in low levels of physical activity saw a substantial survival benefit.

These findings “are good news for breast cancer patients, who can be overwhelmed by the physical activity guidelines, especially during treatment,” when they may be severely fatigued or in pain, Dr. Cannioto said. However, she emphasized, to achieve optimal health benefits, patients and survivors should still strive to meet the guidelines when they are able.

Reducing Self-Reporting Inaccuracies

Although physical activity information that people report themselves is not always accurate, the detailed questionnaire used in this study is likely to provide a better estimate of the amount of exercise that people do than a single question or brief survey would, “giving stronger credence to the findings,” Dr. Schmitz said.

In addition, evaluating the findings according to whether participants did or did not meet the physical activity guidelines, as the study authors did, rather than on how many minutes of physical activity people did each week, is also likely to reduce inaccuracies, said Richard Troiano, Ph.D., also of DCCPS’s Epidemiology and Genomics Research Program.

One limitation of observational studies like DELCaP and the many other epidemiologic studies that form the basis for the latest exercise guidelines for cancer survivors, Drs. Troiano and Elena said, is that such studies cannot definitively prove a cause-and-effect relationship between physical activity and improved survival or reduced risk of recurrence.

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That’s because it’s also possible that “the people who feel better are more likely to be able to be physically active than those who are sicker,” Dr. Troiano explained.

Another limitation is that the DELCaP study only had information on patient deaths due to any cause, rather than on deaths due specifically to breast cancer, and physical activity may have less of an impact on breast cancer mortality, Drs. Schmitz and Troiano noted.

Move as Often as You Can, Whenever You Can

“This study comes at a time when we already have national and international physical activity recommendations for cancer survivors, for the purpose of reducing the risk of recurrence and mortality,” Dr. Schmitz said, and the new findings reinforce these recommendations.

It’s important to keep in mind, however, that “physical activity is not the only factor that determines whether breast cancer will recur, and it certainly is not the only determinant of death. It’s just one piece of the puzzle,” Dr. Elena said.

“We don’t want someone to think, ‘If I exercise enough, I won’t have a recurrence,’” she continued. “But if you can add physical activity into your day, it is likely to influence many types of health outcomes for breast cancer survivors.” That includes quality of life, anxiety, fatigue, and the ability to tolerate treatment, as well as the risk of dying.

The bottom-line message for breast cancer survivors, Dr. Elena concluded, is “Move as often as you can, when you can.”


— Update: 03-01-2023 — cohaitungchi.com found an additional article Effects of exercise on breast cancer patients and survivors: a systematic review and meta-analysis from the website www.ncbi.nlm.nih.gov for the keyword exercise and breast cancer.

Methods

We searched the following electronic databases to March 2005: Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, CancerLit, CINAHL, PsychINFO, PEDro and SportDiscus. The breast cancer specialized register maintained by the Cochrane Breast Cancer Group was also searched. We used search terms related to breast cancer (e.g., breast neoplasms, mastectomy, axillary dissection), exercise (e.g., exercise, physical activity, sport) and publication type (e.g., random allocation, clinical trial). This search strategy was modified as necessary for each database; appropriate non-English language publications were not found. To locate unpublished research, we reviewed proceedings from major cancer and sports medicine meetings as well as clinical practice guidelines for breast cancer, and we searched Web sites housing clinical trial details, theses or dissertations. In addition, we hand-searched the reference lists of all potentially relevant studies and contacted experts and authors of previous studies to identify relevant articles.

Studies were considered eligible for inclusion if they were RCTs comparing exercise with a placebo, controlled comparison or standard care. For the purposes of the review, exercise was defined as a form of leisure-time physical activity that was performed on a repeated basis over an extended period of time, with the intention of improving fitness, performance or health.15 Studies with an additional treatment arm or combined intervention (e.g., exercise with diet modification) were included only if the effects of exercise could be isolated. Exercise studies that included cancers other than breast cancer were excluded unless separate data were available for the breast cancer subgroup. Therapeutic exercise regimens addressing only specific impairments related to the shoulder, arm or both were not included. A priori, we excluded reports that were available only in abstract form.

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Trials were included only if they involved women with early to later stage (Stage O–III) breast cancer or who had undergone breast cancer surgery with or without adjuvant cancer therapy. Studies were required to have as a primary outcome quality of life, cardiorespiratory fitness or physical functioning. Secondary outcomes of interest included symptoms of fatigue and body composition (body weight or body mass index [BMI]). We also extracted data on adverse events resulting from the exercise intervention.

Two independent reviewers (MLM, KLC) screened the titles and abstracts of identified studies for eligibility. Papers deemed potentially relevant were obtained, and the full papers were reviewed for inclusion by the same 2 independent reviewers. Information on patients, methods, interventions, outcomes and adverse events were extracted from the original reports by the 2 independent reviewers onto paper forms that they had designed and pre-tested. Disagreements were resolved by consensus (MLM, KLC, KSC). The methodologic quality of each RCT was assessed using the following criteria:

1) Was there adequate concealment of allocation?

2) Was the method of randomization well described and appropriate?

3) Was the outcome assessment described as blinded?

4) Was the method of blinding of the assessment of outcomes well described and appropriate?

5) Was there a description of withdrawals and drop-outs?

6) Was the analysis intention-to-treat?

7) Were withdrawals and drop-outs less than 10%?

8) Was adherence to the exercise intervention (attendance or completion of exercise session) greater than 70%?

All items were scored as positive (+), negative (–) or unclear (?). Studies were defined as being of “high quality” if they fulfilled 4 or more of the 8 quality criteria.

Study results were pooled, if appropriate, using random effects models after heterogeneity among the trials was considered. For continuous outcomes, individual study mean differences were reported; pooled statistics were calculated using weighted mean differences (WMD) when data were on a uniform scale and using standardized mean differences (SMD) when data were on different scales. All results were calculated with 95% confidence intervals (CIs). The estimated effect size was calculated for outcomes that were reported in 3 or more studies. For dichotomous variables, individual and pooled statistics were calculated as odds ratios (ORs) with 95% CIs. Heterogeneity was tested using a χ2 test that considered a p value of less than 0.10 to indicate significant heterogeneity. When heterogeneity was evident and could be explained by clinical dissimilarities, trials were not pooled.

References

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