Regular exercise following a diagnosis of breast, prostate, or colon cancer has been linked to improved survival, and the same appears to be true for seven less commonly studied cancers, new data suggested.

Pooled data from six cohort studies revealed that a higher level of moderate-to-vigorous leisure-time physical activity after a cancer diagnosis was associated with a lower risk for cancer mortality among survivors of bladder, endometrial, lung, and ovarian cancers, with benefits seen even at activity levels below current physical activity recommendations.

Engaging in leisure-time physical activity at levels equal to or greater than current recommendations was associated with a lower risk for cancer mortality among survivors of oral, rectal, and ovarian cancers compared with no physical activity, though not all associations were statistically significant. Similar results were observed among kidney cancer survivors, although no findings reached statistical significance.

Additionally, lung and rectal cancer survivors who met physical activity guidelines after their diagnosis had a lower risk for cancer mortality, even if they did not meet guidelines before diagnosis.

The authors do acknowledge the potential for reverse causality, in which sicker patients may be less physically active because of deteriorating health.

Still, “collectively, these findings support recommendations for regular physical activity beyond commonly studied cancer types,” Chao Cao, PhD, MPH, Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, wrote in an invited commentary.

The study and commentary were published online on February 17 in JAMA Network Open.

Addressing a Data Gap

Current physical activity guidelines for cancer survivors advise 150-300 minutes of moderate-intensity activity or 75-150 minutes of vigorous-intensity activity per week, equivalent to 7.5-15.0 metabolic equivalent task hours per week (MET-h/wk).

However, much of the evidence for that advice has come from observational studies of breast, colon, and prostate cancers — leaving uncertainty about other cancer types.

To address this knowledge gap, Erika Rees-Punia, PhD, with the American Cancer Society, and colleagues pooled data from six long-running US cohorts to examine the moderate-to-vigorous leisure-time physical activity and cancer mortality among survivors of bladder, endometrial, kidney, lung, oral cavity, ovarian, and rectal cancers.

The pooled analysis included 17,141 survivors (mean age, 67 years; 60% women). All six cohorts assessed physical activity every 2-8 years, and over an average follow-up of about 10 years, 4872 participants died of cancer.

Compared with survivors reporting no moderate-to-vigorous leisure-time physical activity, even low levels of activity (> 0 but < 7.5 MET-h/wk) were associated with a significantly lower risk for cancer mortality among three groups: survivors of bladder (hazard ratio [HR], 0.67), endometrial (HR, 0.62), and lung cancers (HR, 0.56).

Meeting guideline levels of physical activity (7.5 to < 15.0 MET-h/wk) was associated with further reductions in mortality risk for endometrial (HR, 0.40) and lung cancers (HR, 0.38), and the same reduction for bladder cancer (HR, 0.67).

But is more exercise better?

For oral cancer, it appeared so. Engaging in at least double the recommended physical activity level was associated with a lower cancer mortality risk among oral cancer survivors (HR, 0.39 for > 22.5 to 30.0 MET-h/wk; and HR, 0.36 for ≥ 30.0 MET-h/wk). The association was not significant for activity levels below this threshold.

However, for rectal cancer survivors, only one physical activity level was associated with a significantly lower mortality risk (HR, 0.57 for >15.0 to 22.5 MET-h/wk), though activity levels of at least 7.5 MET-h/wk suggested a favorable association. And although estimates for cancer mortality among kidney cancer survivors suggested a lower mortality risk at all activity levels, the associations did not reach statistical significance.

Importantly, by leveraging repeated measures of physical activity before and after a cancer diagnosis, the researchers found that survivors of lung and rectal cancers who became active only after their diagnosis appeared to benefit from exercising, even if they had not previously met activity guidelines. Lung cancer survivors who met guidelines after diagnosis had a 42% lower risk for cancer mortality (HR, 0.58) and rectal cancer survivors who met guidelines after diagnosis had a 49% lower risk (HR, 0.51) than those inactive both before and after diagnosis.

However, meeting physical activity guidelines only before diagnosis, but not after, was not associated with a reduced likelihood of cancer mortality for survivors of any cancer type.

These “findings reinforce the importance of promoting regular physical activity after diagnosis” as well as “the need for cancer-specific, precision-informed strategies to support an active lifestyle across diverse survivor populations,” Cao wrote in the invited commentary.

Cao said the availability of repeated physical activity assessments across all cohorts overcomes a “key limitation” of prior studies that relied on single timepoint measures after diagnosis and “provides valuable insights into the impact of long-term habitual physical activity.”

The authors agreed, while also acknowledging the potential for reverse causality, in which sicker patients may be less physically active because of declining health.

H. Gilbert Welch, MD, MPH, Center for Surgery and Public Health, Brigham and Women’s Hospital, Boston, who wasn’t involved in the study, elaborated on this point.

“The authors themselves highlight the major threat to the inference that exercise helps cancer patients live longer,” Welch told Medscape Medical News. “Simply put, healthier and more advantaged patients are able to exercise more, and they live longer simply because they are healthier and more advantaged.”

While Welch would still encourage exercise in general and for cancer patients, “the finding may have nothing to do with exercise,” he said. It’s “virtually impossible to get around this problem with observational data.”

That’s why Welch used to tell his own patients this: “the reason to exercise is less about reducing your risk of death in the future, more to feel better — and sleep better — now.”

The study was funded by the American Cancer Society. Rees-Punia and Cao had no disclosures. Welch reported receiving royalties from books including Should I Be Tested for Cancer?