[thedoc (OP)]

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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Asked by Brandon Lewis


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[thedoc (OP)]

We answered this question on the show...



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.
[img float=right]/forum/copies/RTEmagicC_EM_of_pap_virus__basal_tissue_grafted_to_mouse_04.jpg.jpg[/img]Hannah[/b] -   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.

[CliffordK]

Genital Warts is a highly communicable disease, while not actually transmitting cancer, it greatly increases the cervical cancer risk in women.  Fortunately there is now a good HPV vaccine.  Several other viruses are also considered Oncoviruses, and can increase the risk of cancer.  A couple of types of bacteria have also been associated with cancer.

Theoretically one could transmit metastatic cancer with blood transfusions, but the risk is exceptionally low in "healthy" recipients.  Blood donors are excluded if they have a history of cancer, and your body would naturally fight the invading cells as "foreign". 

Here is an abstract that indicates no increased risk of developing cancer of recipients of blood donations from "pre-cancerous" patients.

Organ transplants, are a much greater risk for transmitting cancer for two reasons.  First of all, the organs are matched to the recipient with a much greater antigen match than would otherwise be used with a blood donation.  And, to prevent organ rejection, the patients are given immune system suppressants which would also limit the body's ability to fight the invading foreign tissue.

Identical twins, of course, would have the same cancer risks of developing new cancers, but as you mentioned, would have difficulties recognizing the tissue from the other as being "foreign".

The cancer in the Tasmanian Devils is considered to be Clonally Transmissible Cancer.  There is no known wild clonally transmissible  cell line in humans, although a few individual cases of transmission have been documented.  The wikipedia article suggests that there is a clonally transmissible cancer in dogs and hamsters.

I presume Tasmanian devils are at greater risk than humans for cancer propagation due to their nipping and biting, and presumably drawing blood in ordinary social interactions.  This is also an interesting note about the Tasmanian Cancer, and relative gene stability, although there are apparently a few different cell lines now.

Since humans are less likely to bite and draw blood, perhaps it offers some amount of protection, although one could imagine a kissing cancer, or perhaps sexual transmission as occurs with dogs.

[Lor]

i heard somewhere that people long ago believed cancer was contagious-it was thought to be an old wives tail but now we're finding out viruses are the trigger in many cases.My grandmother died from non hodgekins lymphoma and i recently read that anyone who has had a serious staph infection (of which i remember her being hospitalized for)has a high chance of getting this cancer-so i guess bacteria could also be carcinogens (?) if you could call them that.

[John]

My wife has been a cancer nurse for 25 years. She was bitten by a patient on her forearm about 15 years ago. About 5 years ago she developed an ugly looking mole directly on the scar from the bite. It was tested and was confirmed as melanoma cancer. It was removed and lymph node testing was done and all was negative. I truly doubt if this was coincidental as the cancer formed on the direct site of the bite