Prevalence and risk of occult cancer in stroke

Cancer is associated with higher risk of stroke. Whether this translates into higher risk of cancer in stroke of an extent calling for cancer screening in stroke is unclear. We investigated prevalence and risk of occult cancer in stroke compared to the background population without history of stroke.

All patients >40 years of age with incident stroke in Denmark 2003-2015 were identified through the Danish Stroke Registry (n = 85 893) and matched 1:10 on age and sex to the Danish background population without history of stroke (n = 858 740). Linking data to the Danish Cancer Registry, we determined prevalence of occult cancer in stroke defined as the event of previously unknown cancer during a 1-year follow-up in the stroke and in the background population. Cox regression models were used to study risk in comparison to the background population.

Prevalence (per 1000) of occult cancer in the stroke/background cohorts was 25.0/15.8 in women and 29.8/20.4 in men. Prevalence was dependent on age and sex. Highest among stroke patients aged 70-80 years (35.6 in women, 42.4 in men); lowest in patients aged 40-50 years (8.3 in women, 6.8 in men). Stroke was associated with an overall 54% higher risk of occult cancer but risk increased significantly with smoking, hazard ratio (HR) 1.47, age HR 1.27 per 10 years, male sex HR 1.25, and diabetes HR 1.25.

Prevalence and risk of occult cancer in stroke is considerable and calls for attention when designing the stroke investigation program.