Exercise After Cancer Treatment

There is a specific figure here, and it is not vague. It comes from the Physical Activity Guidelines for Americans, 2nd edition. The U.S. Department of Health and Human Services released it in 2018. It asks adults to do one of the following each week.

• 150 to 300 minutes of moderate-intensity aerobic activity, or
• 75 to 150 minutes of vigorous aerobic activity, or
• an equivalent combination of the two.

Two additions come with that. Muscle-strengthening work on at least 2 days a week. And, for older adults, balance training on top of the other two.

One line matters more than the totals for anyone rebuilding after treatment. The guidelines say this activity can be done in episodes of any length. There is no minimum block. Ten minutes counts. Three minutes counts.

Intensity is measured in METs. That is short for metabolic equivalent of task. One MET is the rate of energy a person uses sitting at rest.

• Light-intensity activity expends less than 3 METs.
• Moderate-intensity activity expends 3 to 6 METs.
• Vigorous activity expends 6 or more METs.

Sedentary behavior has its own definition. It is any waking behavior using 1.5 or fewer METs while sitting, reclining, or lying down. Most office work counts. So does driving, and sitting to watch television.

NCI makes a point that gets lost easily. A person can be active and still spend a lot of time sedentary. These are two separate measures, not two ends of one scale.

In 2018 the American College of Sports Medicine convened a roundtable on physical activity and cancer. Experts came from many countries and many fields. Its report is unusually clear about where the evidence is strong, and where it runs out.

It concluded that exercise training and testing are generally safe for cancer survivors. It said every survivor should keep up some level of physical activity. Its own phrasing for the core message was to "avoid inactivity."

The graded findings:

• Strong evidence that moderate aerobic training, resistance exercise, or both can help. During and after cancer treatment, they can reduce anxiety, depressive symptoms, and fatigue. They can also improve health-related quality of life and physical function.
• Strong evidence that exercise training is safe in people who have, or might develop, breast-cancer-related lymphedema.
• Some evidence that exercise benefits bone health and sleep quality.
• Insufficient evidence that activity helps prevent heart damage, or the nerve damage chemotherapy can cause. Evidence is also insufficient for cognitive function, falls, nausea, pain, sexual function, and treatment tolerance.

That last point is the honest part. Some people hope exercise will protect the heart during treatment. Some hope it will prevent nerve damage in the hands and feet. The evidence does not yet support either. That does not make the exercise pointless. It changes what to expect from it.

An earlier roundtable in 2010 reached the first version of these conclusions. It found survivors could safely do enough exercise training to improve fitness. It also found they could restore physical function, improve quality of life, and reduce cancer-related fatigue. The 2018 group aimed higher. It set out to move past general public-health advice, toward plans built for specific cancer types, treatments, and outcomes.

Research has raised the possibility that physical activity has beneficial effects on survival after some cancers. NCI gives figures for three, and labels the strength of each.

Breast cancer. A 2019 systematic review and meta-analysis pooled observational studies. Breast cancer survivors who were most active had a 42% lower risk of death from any cause. They had a 40% lower risk of death from breast cancer. The comparison was with those who were least active.

Colorectal cancer. Evidence from several studies points the same way. Activity after a colorectal cancer diagnosis is linked to a 30% lower risk of death from that cancer. It is linked to a 38% lower risk of death from any cause.

Prostate cancer. Here the evidence is limited, from a few studies. Activity after a prostate cancer diagnosis is linked to a 33% lower risk of death from that cancer. It is linked to a 45% lower risk of death from any cause.

For other cancers, including non-Hodgkin lymphoma, stomach cancer, and malignant glioma, NCI describes the evidence for survival benefit as very limited.

Now the caveat that belongs beside every one of those figures. These are observational findings. NCI says such studies cannot fully rule out one thing. Active people may have better outcomes because they also do other healthy things. Randomized trials assign people to exercise, and give the strongest evidence. They remove bias from illness that was already present, and from the inactivity that comes with it.

Those trials are running now. NCI names three. The Breast Cancer Weight Loss trial, known as BWEL, in newly diagnosed breast cancer patients. The CHALLENGE trial, in colon cancer patients who recently finished chemotherapy. And INTERVAL-GAP4, in men with metastatic, castration-resistant prostate cancer.

The roundtable conclusion that exercise is generally safe is a statement about populations. Individual situations change it. A few specifics are worth raising.

• Which movements, if any, should be avoided after this particular surgery, and for how long?
• Are there restrictions from bone metastases, a low platelet count, a central line, or a stoma?
• For anyone with lymphedema or at risk of it: how should resistance training be introduced, given that the evidence says it is safe?
• Is there a cancer rehabilitation program, physical therapy referral, or survivorship exercise program available here?
• What does the balance-training part of the guidelines mean for someone with neuropathy in the feet?
• How should activity be adjusted on days when fatigue is worst?

Cancer-related fatigue has the strongest exercise evidence behind it. It is also the reason people stop. Both of those are true at once.

The roundtable found strong evidence that aerobic training, resistance exercise, or both reduce fatigue. That held during and after treatment. It found the same for anxiety and depressive symptoms. Fatigue, mood, and physical function all respond. That combination is what makes movement worth protecting, even on a day when it feels unreasonable.

The "episodes of any length" clause in the federal guidelines is the practical door in. Short sessions add up toward the weekly total.

For the version of this that applies during active treatment, see exercise during cancer treatment. For what comes after an operation specifically, see returning to exercise after cancer surgery. And for the broader picture of life after treatment, see survivorship.

This information is educational and is not a substitute for medical advice.

• NCI — Physical Activity and Cancer
• Physical Activity Guidelines for Americans, 2nd edition, PDF
• PubMed — Campbell KL, et al. Exercise Guidelines for Cancer Survivors: Consensus Statement from International Multidisciplinary Roundtable, PMID 31626055