An article on Daily News Central describes a study conducted in Iceland
that shows  relatives as far out as the fifth degree of connection may
be more likely to develop cancer if someone in their family has the
disease. This is true of the most common forms of cancer, the article
says. If a relative has colon cancer, for example, risk of other forms,
such as stomach cancer, might be higher than in the general population.
Environmental and lifestyle factors also play a role, but the study
shows strong evidence of the family connection.
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http://health.dailynewscentral.net/content/view/000246/31/