The first meta-analysis on the question suggests that preserving these factors significantly improves survival.
Cancer patients with higher physical fitness and muscle strength are less likely to die prematurely, a large systematic review has found.
An international team led by researchers from Edith Cowan University in Western Australia analysed 42 studies, with a total of 47,000 patients, that measured either cardiorespiratory fitness and/or muscle strength and compared it with all-cause and cancer-specific mortality.
The paper, published in the British Journal of Sports Medicine, claims to be “the first meta-analysis to investigate the association between physical fitness components measured after cancer diagnosis and all-cause and cancer-specific mortality”, and to analyse the associations by cancer type and stage.
Cancer patients with high muscle strength had a 31% lower risk of all-cause mortality than those with low muscle strength, when 22 studies were meta-analysed. Low muscle strength was defined as grip strength of <13kg to <25kg in women and from <20kg to <40kg in men.
For patients with advanced cancer, the risk was up to 46% lower.
The benefits were greatest for patients with digestive cancers, with a 41% lower risk, followed by lung cancer patients with a 19% reduction.
Cancer patients with high levels of cardiorespiratory fitness had a 46% reduction in all-cause mortality compared with those of low cardiorespiratory fitness. The 13 studies analysed for this result showed some evidence of publication bias.
For early-stage cancer, the association between fitness and mortality was not significant.
Lung cancer patients had the greatest survival benefit from fitness with a 31% reduced risk. The authors suggest that this could be related to the fact that lung cancer takes a greater toll on fitness than other cancers, “and, therefore, preserving CRF levels is of utmost importance when dealing with lung cancer”.
Similar associations appeared when analysing unit increments in fitness and strength as when comparing high and low.
Fewer studies looked at cancer-specific mortality, which had only a non-significant inverse association with cardiorespiratory fitness. There were not enough studies on cancer-specific mortality by cancer stage and type to analyse.
The authors say their findings “emphasise the importance of examining muscle strength and CRF [cardiorespiratory fitness] in clinical practice to determine the mortality risk in patients with cancer, especially those with advanced cancer.
“Furthermore, implementing tailored exercise prescriptions to enhance muscle strength and CRF in patients with cancer may help to reduce cancer-related mortality.”
