Exercise before bowel surgery barely moved fatigue scores in 518 patients

Prehabilitation is a tidy idea: if people are fitter going into an operation, they should come out of it better. Much of the enthusiasm for it rests on that logic rather than on outcome data.

A randomized trial has now been mined for what it says about one of the outcomes patients care about most: the exhaustion that follows cancer surgery.

The answer is a faint one, and the researchers say so themselves.

What the operation is

Colorectal cancer is cancer that develops in the tissues of the colon or rectum.

Those are the last stretch of the digestive system. Your colon is the first and longest part of your large intestine, and your rectum is the lower part of your large intestine. Cancer that begins in the colon is called colon cancer, and cancer that begins in the rectum is called rectal cancer.

Surgery to remove part of the bowel is a large operation with a long tail. The researchers set out the problem plainly: fatigue after cancer surgery is common and evidence suggests it could be alleviated by physical activity.

That it is common is the part this paper establishes. It is also the part that makes an intervention as cheap as walking more worth testing at all.

What the trial did

PHYSSURG-C was a multicenter, controlled, randomized trial.

Patients diagnosed with colorectal cancer were randomized to additional unsupervised moderate physical exercise in accordance with WHO guidelines or usual care, two weeks before and four weeks after surgery.

The guideline being followed is the familiar one: at least 150 minutes of moderate-intensity physical activity per week.

Two features of that design shape everything after it. The window is short, six weeks in total around the operation. And the exercise was unsupervised, so what the intervention group actually did is not directly measured.

Outcomes were collected with trial-specific questionnaires at baseline, at 4 weeks and 12 months, covering self-reported fatigue as well as quality of life, pain, and mental recovery. A total of 518 patients were included in this analysis.

The thing to understand before the numbers

This is not the question the trial was built to answer.

The authors describe it as a post hoc exploratory study analyzing fatigue and other secondary outcomes from a trial aimed at exploring if prehabilitation by additional physical activity could improve postoperative recovery.

Post hoc means the analysis was designed after the data existed. Exploratory means it is looking rather than testing. Both labels are honest and both should change how much weight the result carries, because a study that examines many secondary outcomes will produce some that look notable by chance alone.

What the fatigue scores did

There was a difference, and it was consistent in direction. In a per protocol analysis at 4 weeks the mean difference was 4.04, and at 12 months it was 4.29, favoring the exercise group.

Consistency across two time points a year apart is the strongest thing here.

The weakness is in the precision. At 4 weeks after surgery, the mean difference in fatigue was 3.75 with an intention to treat approach, and the range around that figure reaches almost exactly to no difference at all. A result that only just excludes zero, in an analysis that was not planned in advance, is a hint.

And the other outcomes flatly did not move. There were no differences between the intervention and control groups regarding quality of life, pain, or mental recovery.

Why the better-looking number is the less trustworthy one

The twelve-month figure comes from a per-protocol analysis, and that deserves unpacking because it recurs across exercise research.

Analyzing by intention to treat means everyone stays in the group they were randomized to, whether or not they did the exercise. It usually makes the result look worse, and it is what protects the comparison, because randomization is the only thing guaranteeing the two groups were otherwise alike.

Per protocol keeps only the people who complied. That sounds like a fairer test of the treatment and is not, because the people who complete an exercise program during cancer treatment are, on average, the people who were better able to. Health predicts adherence as much as adherence predicts health.

So in this paper the pattern runs the wrong way for confidence: the analysis that preserves randomization gives the faintest result, and the stronger numbers come from the analysis that does not.

What a four-point difference means

Less than you would hope, because of how it was measured.

The outcomes came from trial-specific questionnaires rather than one of the standard fatigue instruments used across cancer research. That makes the scale hard to compare with anything else, and it means there is no established threshold for how many points a patient would have to move before noticing.

Four points on an unfamiliar scale is a number, not yet an experience.

What this cannot establish

It cannot establish that prehabilitation reduces fatigue, and the authors do not claim it does. Their conclusion is that the study found a suggestion of less postoperative fatigue in the intervention group.

It cannot say how much exercise was done, because none of it was supervised.

It cannot separate the before-surgery part from the after-surgery part, since patients got both.

And the phrase the authors end on is the most candid in the paper: further studies are needed to define the role of unsupervised moderate exercise, if any, before and after surgery in regard to postoperative fatigue in patients with colorectal cancer. Researchers do not usually write “if any” about their own intervention.

The paper is paywalled, so the authors’ own limitations section was not available for this piece.

What someone facing bowel surgery should take from it

Not a reason to start an exercise program on the strength of this result, and not a reason to skip one either.

The case for moving more before an operation does not depend on this analysis. Physical activity contributes to the prevention and management of noncommunicable diseases such as cardiovascular diseases, cancer and diabetes, and being fitter going into major surgery is supported by a broader literature than one exploratory look at one trial.

What this study adds is a caution about how much to expect. Unsupervised moderate exercise, over six weeks around an operation, did not clearly change quality of life, pain or mental recovery, and moved fatigue by an amount the trial itself can barely distinguish from nothing.

The practical version is to raise it with the surgical team, who can judge what is safe for a specific operation and a specific person. That conversation is worth more than the four points.