Impact of Physical Activity on Metastatic Cancer at Diagnosis and Mortality: Results from the Lifelines Cohort Study

Background: While higher pre-diagnosis physical activity is associated with lower mortality among cancer survivors, it is unclear whether this is partly due to a reduced likelihood of metastatic cancer at diagnosis. This study evaluated the relationship between adherence to physical activity guidelines prior to cancer diagnosis and both all-cause mortality and the risk of being diagnosed with metastatic cancer at initial presentation. 
Methods: In the prospective Lifelines Cohort Study of 152,915 adults, we identified individuals diagnosed with primary cancer at any site through linkage to the Netherlands Cancer Registry. Adherence to physical activity guidelines was defined as engaging in at least 150 minutes of moderate-intensity activity, 75 minutes of vigorous-intensity activity, or an equivalent combination of both per week. Cox and logistic regression were used to estimate adjusted hazard ratios (aHRs) and odds ratios (aORs) with 95% confidence intervals (CIs) for the association between adherence to physical activity guidelines, all-cause mortality, and the presence of metastatic cancer at diagnosis. 
Results: A total of 5,990 cancer patients were included, of whom 10.7% did not engage in any physical activity, 19.1% were insufficiently active, and 70.2% were sufficiently active. Cancer patients who adhered to physical activity guidelines prior to diagnosis had a 16% lower risk of all-cause mortality compared to those who reported no physical activity (aHR 0.84; 95% CI: 0.72–0.98). However, adherence to physical activity guidelines was not significantly associated with a reduced likelihood of metastatic cancer at diagnosis (aOR 0.98; 95% CI: 0.79–1.23).
Conclusion: Physical activity at recommended levels is linked to a reduced mortality risk among cancer survivors. This association cannot be explained by a lower likelihood of metastatic cancer at diagnosis in physically active individuals.