Why “how you live” during cancer treatment might affect outcomes

The backstory: Cancer is rising globally, and inactivity is common

Around 20 million new cases and 9.7 million deaths were caused by cancer globally in 2022, and experts predict that this number will rise significantly by mid-century due to an ageing and growing global population.

Cancer affects a large proportion of the UK population every day, with about 423,900 individuals receive a diagnosis annually.

In the UK, cancer claims the lives of about 168,000 individuals annually.

Notably, there was an increase of almost 19% in cancer diagnoses from 2012 to 2022, but a decrease of about 10% in age-standardised mortality rates during the same time frame. This indicates that there has been improvement in prevention, detection, and treatment, despite the overall burden increasing.

NHS mortality data show that the number of cancer deaths in England increased from 2013 to 2023. However, the age-standardised cancer mortality rate decreased over the same period. For men, it fell from 338 to 294 per 100,000, and for women from 231 to 208 per 100,000. Meaning that although the total number of cancer deaths rose, the age-adjusted risk of dying from cancer declined.

There has been a rise in physical inactivity in recent years, which is one reason why public-health experts have identified inactivity as a risk factor for a wide variety of diseases, including breast and colon cancer. In 2022, over 31% of adults did not reach the required levels of physical activity.

In England, according to “Active Lives 2023–24”, approximately 63.7% of adults were physically active for 150 minutes or more per week, whereas around 25.4% did not engage in any regular physical activity. However, several demographic variations have emerged:

• Age: Activity continues to grow significantly among older adults. Those aged 75+ have reached their highest recorded activity levels, with 42.8% now active, up from 33.4% in 2016. Conversely, activity among young adults (16-34) has declined over the long term, stabilising only recently.
• Gender: Men are more likely to be active (approx. 66%) than women (approx. 61%).
• Deprivation: A stark “activity gap” persists; 68.6% of adults in the least deprived areas are active, compared to only 55.5% in the most deprived areas.
• Ethnicity: People from mixed ethnic backgrounds (70.8%) are the most likely to be active, while those from Asian and Black backgrounds (both approx. 55%) remain below the national average

These figures are significant since inactive time isn’t merely “the opposite of exercise.”

Large-scale analyses link higher sedentary behaviour to increased risk of several cancers (including colon and endometrial) and to higher overall cancer mortality. When comparing higher levels of sedentary activity to lower levels, one review found a link with all-cancer mortality (with an 18% relative risk of dying).

The Big-Ticket Events

Breast cancer: lifestyle during chemotherapy and treatment response.

A randomised trial involving women with Stage I–III breast cancer evaluated a home-based fitness and nutrition intervention administered by oncology nutritionists during chemotherapy. The intervention improved reported exercise and diet quality. The relative dosage intensity (RDI) of chemotherapy did not alter overall (RDI ~93% in both groups), but the intervention group had a much higher pathologic complete response (pCR) rate (53% vs. 28%) among women getting chemotherapy before surgery.

That is not a small outcome. pCR (which means that on examination under the microscope there is no active cancer) is widely used as a prognostic marker and is a sign that medication is working biologically in some forms of breast cancer. The study does not establish that exercise is a “drug,” but it does support a serious, testable idea: the host’s environment during chemotherapy might affect how effectively the treatment works.

Colon Cancer: Structured exercise after adjuvant chemotherapy for colon cancer increases survival.

The Phase III CHALLENGE study evaluated a 3-year structured exercise regimen initiated shortly after the completion of adjuvant chemotherapy for Stage III (or high-risk Stage II) colon cancer.

Important results that were reported after an extended follow-up:

• 5-year disease-free survival: 80% (exercise) vs 74% (education materials), HR 0.72 (28% lower risk)
• 8-year overall survival: 90% (exercise) vs 83% (education materials), HR 0.63 (37% lower risk)

This is the kind of discovery that transforms the way people talk in clinics. It connects a behavioural intervention to outcomes that patients care about, including recurrence and survival, after standard therapy.

It was also refreshingly realistic: the program didn’t say, “Everyone run marathons.” Participants choose the type and amount of aerobic activity they do, and they receive coaching to help them do more and keep it up. There were more musculoskeletal problems in the exercise group, which is what you’d expect when more people are active. This shows that implementation involves coaching, progression, and safety screening, not just motivation.

Lifestyle “bundles” (activity + food + weight): indicators in survival cohorts.

Even prior to the maturation of survival randomised clinical trials, research indicated that integrated lifestyle patterns are significant. A JAMA Oncology study of patients with Stage III colon cancer found that those who followed the American Cancer Society’s nutrition and physical activity guidelines more closely (a combination of activity, diet, and body weight) had a higher 5-year survival rate (85% vs. 76%) and a much lower risk of death.

That study is observational, so it can’t estbalish causation, but it fits with the direction of the CHALLENGE experiment.