Even when heart cancer does occur, it’s 30 to 40 times more likely to be secondary, meaning that it spreads to the heart from somewhere else rather than starting there. So what makes heart cancer so rare? There might be more to the relationship between cancer and the heartBecause heart cancer is so rare, it has not been researched as extensively as some other cancers. Understanding how deep the connection between heart health and cancer goes could allow doctors to detect cancer earlier. Statistically, you probably won’t have to worry about getting heart cancer any time soon.