They found raised risks of blood clots forming in the veins among survivors of most cancers, ranging from approximately a two- to ten-fold increase in risk for different cancer sites. Risks decreased over time but were still elevated for more than five years after the cancer diagnosis. Survivors of half of the 20 cancers studied also faced increased risks of heart muscle damage, known as cardiomyopathy, and heart failure.
For example, survivors of blood, oesophagus, lung, kidney and ovarian cancers were more than one and a half times more likely to experience cardiomyopathy or heart failure than people with no prior cancer.
An increased risk of coronary artery disease and stroke was found in some cancer survivors, including those with prior blood cancers.
The researchers stress that for many people the overall risks will still be low, particularly for younger cancer survivors, but say the findings highlight the need for new strategies to prevent and manage heart and circulation problems in cancer survivors, including a need to raise awareness among GPs of the raised risks.
While the researchers could not definitively identify the causes of the increased risks, the team's analysis suggests that exposure to cancer treatments such as chemotherapy is likely to play a key role.
Lead author Helen Strongman from the London School of Hygiene & Tropical Medicine said: "Over recent decades cancer treatment and management have improved substantially, resulting in a large and growing population of long-term cancer survivors. Around half of those diagnosed with cancer in developed countries are now expected to survive for more than 10 years. However, there are concerns that there may be increased long-term risks of cardiovascular disease following cancer diagnosis, driven by treatment side-effect effects and the potential impact of the cancer itself."
While previous studies have demonstrated the short- to medium-term increased risk of cardiovascular disease from some specific cancer treatments, there have been limited data on the overall and long-term differences in cardiovascular risk between cancer survivors and those who have never had cancer.
To address this, the team brought together anonymised data from primary care, hospitals, cancer registries, and death certificates, to quantify the absolute and relative risks of a comprehensive range of cardiovascular diseases in survivors of the 20 most common adult cancers compared with cancer-free general population controls. The research also accounted for other risk factors for cardiovascular disease, such as older age, smoking and body mass index.