Some biologics (i.e. those that block TNF) may lead to a slightly increased risk of lymphoma, a form of blood cancer. However, the chances of getting lymphoma are very small.
Watch the video below for a visual representation of the risk of lymphoma. The video will also compare this risk to the chances of getting into a car accident.
To summarize: For patients with IBD who are not taking a biologic medicine, 2 out of 10,000 may develop lymphoma. For those on certain biologics, another 4 out of 10,000 may get lymphoma. Therefore, there is around a 6 out of 10,000 chance of developing lymphoma each year.