People who engage in regular physical activity before receiving a cancer diagnosis may be helping to lower the risks of both disease progression and death.

That is the conclusion of an international team of researchers whose study is published online today (8 January) in the British Journal of Sports Medicine.

The article’s first author is Ntokozo Mabena, who is based at Discovery Vitality, Sandton, South Africa. Mr Mabena and his colleagues found that even relatively low levels of physical activity may be advantageous.

There is compelling evidence that physical activity has a key part to play in lowering the risk of death from cancer, but the evidence isn’t as conclusive for its role in disease progression, explain the researchers.

Discovery Health Medical Scheme

To explore this further, the researchers analysed anonymised data from the Discovery Health Medical Scheme (DHMS), linked to the Vitality health promotion programme. The DHMS is the largest open medical plan in South Africa, covering some 2.8 million beneficiaries.

All Vitality programme participants are rewarded for adopting healthy lifestyle behaviours, earning points for physical activity, recorded by activity trackers, logged gym attendance, or registered participation in organised fitness activities.

Activity type, frequency, duration and intensity are recorded and translated into weekly minutes of exercise. In all, 28,248 Vitality programme members with stage 1 cancers, and comprehensive physical activity data for the year preceding diagnosis, were included in the study, which spanned the period from 2007 to 2022.  

Breast and prostate cancers were the most common cancers, comprising 44 per cent of the study total. The length of time between initial diagnosis and disease progression, death, or exit from the study ranged from one month to nearly 13 years. 

Cancer didn’t progress in nearly two thirds of the total sample (65.5 per cent), but did in just over a third (34.5 per cent). And while 81 per cent survived, 19 per cent died before the end of the study. The average time to death was 20 months and the average time to progression was seven months. 

Levels of physical activity in the year before diagnosis were categorised as none recorded (17,457; 62 per cent of participants); low, equal to 60 or fewer weekly minutes (3,722;13 per cent); and moderate to high, equal to 60 or more weekly minutes of moderate intensity physical activity (7,069; 25 per cent).

Lower rates of cancer progression found

After accounting for potentially influential factors, including age at diagnosis, sex, economic and social position, and co-existing conditions, rates of cancer progression and death from any cause were lower among those who were physically active in the year preceding their diagnosis.

The odds of disease progression were 16 per cent lower for those who had engaged in low levels of physical activity in the preceding year than among those who hadn’t recorded any physical activity, while the odds for those who had engaged in moderate to high levels were 27 per cent lower.

Similarly, the odds of death from any cause were 33 per cent lower among those who had engaged in low levels of physical activity compared with those who hadn’t recorded any, and 47 per cent lower for those who had managed moderate to high levels.

‘Physical activity may be considered to confer substantial benefits in terms of progression and overall mortality to those diagnosed with cancer’ [Ntokozo Mabena et al]

Two years on from diagnosis, the likelihood of no disease progression among those with no recorded physical activity in the year before diagnosis was 74 per cent, compared with 78 per cent and 80 per cent, respectively, for those achieving low and moderate to high levels of physical activity. 

While the likelihood of disease progression increased as time went on, it was still lower for those who had clocked up some level of physical activity in the year preceding their diagnosis.

After three years, the likelihood of no disease progression was 71 per cent, 75 per cent, and 78 per cent, respectively, for none, low, and moderate to high levels of physical activity. After five  years, it was 66 per cent, 70 per cent, and 73 per cent, respectively.

Similar patterns were evident for death from any cause. Two years after diagnosis, the probability of survival among those with no documented physical activity in the year preceding diagnosis was 91 per cent compared with 94 per cent and 95 per cent, respectively, among those who had recorded low and moderate to high levels.

The equivalent probabilities of survival three years after diagnosis were 88 per cent, 92 per cent, and 94 per cent, respectively, and 84 per cent, 90per cent, and 91 per cent, respectively, after five years. 

Caveats and conclusions

As the study was observational in nature, cause and effect cannot be established. Mr Mabena and his colleagues acknowledge that they could not account for other potentially influential factors, such as smoking and alcohol consumption, while the data on weight (BMI) were incomplete.

But there are several plausible biological explanations for the findings, they suggest, chief among which is the way in which physical activity strengthens immunity by increasing numbers of natural killer cells, lymphocytes, neutrophils and eosinophils.

Physical activity may also lower the progression risk of hormone sensitive cancers, such as breast and prostate cancers, by regulating oestrogen and testosterone levels, they add.

‘Physical activity may be considered to confer substantial benefits in terms of progression and overall mortality to those diagnosed with cancer,’ Mr Mabena and his colleagues note. 

‘In a world where cancer continues to be a significant public health burden, the promotion of physical activity can yield important benefits regarding the progression of cancer as well as its prevention and management,’ they conclude.

To access the full version of the article – titled Association between recorded physical activity and cancer progression or mortality in individuals diagnosed with cancer in South Africa  Doi: 10.1136/bjsports-2024-108813 – see:
http://press.psprings.co.uk/bjsm/january/bjsm108813.pdf