Can you catch cancer?
Could you get cancer from someone else?
I have heard that sometimes cancer can spread to multiple individuals. In particular, tasmanian devils seem to be suffering from a form of cancer that is transmitted through biting.
Are there instances of cancers being transmitted this way in humans? Say through a blood transfusion? If not, is it theoretically possible, or would the immune system respond? What if the donor and recipient are identical twins?
Brandon (San Francisco, USA)
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Hannah - Let's kick off with sex and yes, cancer can be caused directly by infection with sexually transmitted viruses including the human papilloma virus that causes cervical, anal, and throat cancers. With more...
Margaret - Margaret Stanley in the Department of Pathology at the University of Cambridge. Human Papilloma Viruses are very, very common infections and there's a set of viruses that infect the genital tract and the oral cavity in men and women. 80% of us will have had, or will get, or currently have the infection. It's a very, very common infection, but only about .001% of people who are infected will actually develop the cancer. In women it develops into cancer of the cervix, the second commonest cancer in women worldwide. In men, a rare cancer, cancer of the anus and that's common in gay men. But also, cancer of the tonsil both in men and women but much more common in men than women - 5 times more common, and I have to say, increasing in incidence. What's important is how you get this virus - it's a sexually transmitted infection. And so, with changing sexual practices and behaviour, these cancers are actually becoming more common.
Hannah - And what about catching cancer through donated organs?
James - I'm James Neuberger. I'm Associate Medical Director of Organ Donation and Transplantation in NHS Blood and Transplant. In very, very rare cases, it is possible that the organ that is transplanted will contain cancer cells from the donor. We do our best to screen for this and prevent it, but we cannot prevent it entirely, however good our screening tests are. The second point is that immunosuppresion, which nearly all transplant recipients acquire lifelong, does carry an increased risk of some cancers and it's important that both the patients and their doctors are aware of this increased risk.
Hannah - There's also a risk of picking up cancer through viruses in blood like hepatitis B and C which can trigger cancers in some individuals and can be passed on in donated blood. Although thanks to screening programmes, the risk of this in developed countries is very low. And what about biting? Well, Tasmanian Devils catch cancer on the face through biting, physically transferring cancerous tissue from one Devil to the next. With more.. Elizabeth - Hello, my name is Elizabeth Murchison. I'm at the Wellcome Trust Sanger Institute near Cambridge. So it's actually one single cancer which is transmitted from one animal to another. The Devil's cancer is not recognised or rejected by the new host's immune system even though it's a foreign graft. There are some very rare examples of cancers which are transmitted in this way in humans and these are often associated with mothers getting cancer that are then transmitted through the placenta to the foetus, and even more rarely, vice versa - the foetus develops the cancer which is transmitted to the mother.
Hannah - So, Tasmanian Devils catch cancer through biting whilst humans can catch cancer through sex, transfer between mother and foetus, and there's also a small risk of catching cancer from a donated organ. Thanks to Dr. Elizabeth Murchison, Professor James Neuberger and Margaret Stanley for clearing up that contagious cancer question.