Saturday, March 14, 2009

Oops.. My mistake..


I'd like to correct the mistake i made in the previous post. The one i said cancer cells are produced in our body everyday but our immune system managed to zap them all off.. Well, the statement is INCORRECT. I read about that in one of the health articles i found in the net. Oh oh, feeling real guilty for not remembering which one. But anyway, this is another article i found after much googling on different keywords.

It says, (just a few extracts)

Circulating in the email world is the statement that says “normally, we all have dormant cancer cells in our body.” Implied is the assertion that all healthy people are walking around with a time bomb within them, ready to explode.

The healthy person does not carry any cancer cell in their body, period. If every tissue in the body of a normal person is biopsied, or if a person who dies of any non-cancerous disease, like heart attack or stroke, or trauma, is autopsied from head to foot, no cancer cells will be found. The only exception to this is if the person had an undiagnosed cancer, which is incidentally found on autopsy, a finding that excludes this person from being healthy in the first place.

So, i apologises for the mistake i made.
However, as this article is also found from the net, i'm not sure which one to be trusted.
Perhaps i'll have to do more and more readings after tis.
Suddenly i end up being an oncologist after my MBBS. Hahaha...

Thanks to Global Observer for bringing up that matter in the previous comment. =)
Some findings show that HIV sufferers do have higher risk of getting cancer than normal people. But it seems the exact cause of the higher risk is still on debate. Hurm...


Global Observer said...

It's good to be careful with statistics and what meanings we can read into the statistical results. Using statistics, I can for example, prove you have more than the average number of legs!

Stats isn’t my ‘thing, so I may be taking rubbish, but I remember testing hypotheses at 95% confidence. 1/20. If someone said to me "jump out of this plane, there is only a 1 in 20 chance the parachute will not work" I'd rather stay on the plane. How about you?

To have a 5% margin of error and then claim something like 0.001% of the population is at increased risk of something seems to me a bit strange (and I know there are T tests, Q tests etc...). Stats by its very definition is an approximating science. It’s easy to find data to support whatever side you want. Just look at politicians!!!

As you make your way through the medical profession you may come across another strange statistic... That the results of scientific experiments usually lies in favour of the people who funded that research. Strange that.

There is also the joke that people an 'approval' bodies have a higher rate of financial and personal connections to the board of directors of companies whose products are waiting to be approved. Errrm, it was it a joke right??

One could also ask of the 'HIV/cancer survey' how many of them were taking retroviral drugs for treatment? I don't think many poor Africans and Indians have much access to cancer diagnosis, so I guess most of the people were in western countries and possibly more likely to be able to afford drugs such as AZT etc. Perhaps, if there were people using these drugs, then was that was responsible for the supposed increase risk in cancer? Did they check?

Welcome to the medical world :)

AkMaR said...

ok, this comment is really full of statistical terms.
1/20 chance the parachute will not work? i'll jump out if the chance of the plane crashing is 1/19.

Global Observer said...

Ha ha ha! Quality reply! :D

I made a mess of my last comment. Thanks for tidying it up, but the links are missing...

Errrm, it was it a joke right"
and "retroviral drugs"

J Lee said...

Hmm, I would agree that HIV patients have higher risk of getting cancer, compared to normal individuals, but not because of the failure of the body's immunity to kill cancer cells, but rather because HIV patients are severely immunosuppressed, and therefore are more succeptible to secondary infections from bacteria/virus that have the potential to cause cancer (ie : EBV, HPV, HHV-8).

Regarding cancer, correct me if I am wrong, but i think its true that the body's immune system do play a role in defending againts cancer development by having all sorts of immune cells (Ab, NK, CTL, even Macrophages!) kill cancer cells.

For cancer cells to pop up, there has to be certain accidental gene mutation as a cell is happily dividing. Once a cancer cell pop up, the body MAY be able to kill it in time by using the power of the immune system, before it gets too big.

Regarding HIV patients and the effects of immunosuppression to a NON-EXTERNAL development of cancer, 2 important points to take note :
1. What are the chances of a normal body cell mutating to become a "cancer cell"
2. Can a HIV patient stay alive (yet untreated and un-infected by any secondary virus/bacteria)long enough to hit the billion dollar lottery of a normal body cell mutating to cancer cell?

Sorry for the long comment, but I just found interest in this discussion. :)

Is this your AIR topic?

AkMaR said...

To: J Lee

Not at all, i'm glad u gave a long feedback. At least i get to learn new things.
Nope, this is not my AIR topic, it's only one of the learning issues in PBL.

Ok, so our immune system can kill cancer cells?
That means we may, at anytime have a body cell that mutates into cancer cells, but somehow is successfully killed by our immune system?

J Lee said...

Yeap that is right.

When a cell mutates, the surface of the tumor cell changes.

To simply put it: the cell looks foreign.

And thats exactly what our immune system attacks ---> things that don't belong to ourselves (same way immune system attack incompatible donated organs, and the same way bacteria is attacked)

And so, cancer cells WILL be killed by our immune system. But do note, there are "smart" tumors which have certain mechanisms to try to look the same as normal cells, and there are also some tumors who actually release chemicals that suppress immunity, so that the tumor itself can survive in the body. There are also many other mechanisms that tumors use to avoid being "makan-ed" by the immune cells.

But fact remains that, immune system will defend us againts cancer cells. This will be learnt semester 2 patholgy. However, I am really impressed you took the initiative to learn it now. :) Good job!

Global Observer said...

J Lee. I don't have much time right now so it may be a few weeks before I can come back here to follow up, but I felt the need to say this.

I concede you are more versed in general modern medical practice and cancer theory than I, however I can almost guarantee I am more versed in the psychology of the philosophy of science and cognitive analysis than you.

On what grounds are you basing your agreement that HIV patients are at higher risk? Is it not just a perception? How can the assertion of this risk, come from anything other than from measured mortality or detected and measured cancer rates? In which case, it would surely be discussed not in terms of risk, but as a statement of fact. Just because an idea seems plausible, and may ‘connect’ a number of different elements of medical theory (and fact) together, that is no basis for positively asserting “higher risk”, even if they actually are at higher risk. i.e. there must be a scientific basis first.

You said something which appears to me to be contradictory. How is being "immunosuppressed" different from the "failure of the body's immunity.." as mentioned in your first paragraph?

And if there as you suggest these two things are not the same, then what is the scientific basis for that claim?

Lastly, the factor/influence of the retroviral drugs on patient susceptibility or morbidity wasn't addressed. How can claims be made as to what is responsible for that risk without examining the biological effects of the drugs?

The info you gave was v. interesting.

AkMaR said...

Glad that there is an argument on this matter. I will surely benefit a lot. since i am very new to medical world, i dont think i'll be able to come up with good theory yet but i'll try my best to look more on this.
Thx a lot!

J Lee said...

Global observer,

This discussion is definitely more interesting than my post! :)

To quote you :
"You said something which appears to me to be contradictory. How is being "immunosuppressed" different from the "failure of the body's immunity.." as mentioned in your first paragraph?"

Allow me to explain what that sentence mean. I am saying that HIV patients DO HAVE higher risk of getting cancer, because they are easily infected (due to immunosuppression) with other viruses which cause cancer. Among them are Human Papilloma virus, the cause of cervival and anal carcinoma, Herpesvirus, the cause of a vascular tumor known as kaposi sarcoma, and the list goes on. What I am saying that although immunosuppression itself can directly lead to tumor development, the common cause of tumor development in immunosuppressed individuals is secondary viral infections. Hence, HIV patients as well as patients with other types of immunosuppression (like transplant recipients or X-linked lymphoproliferative syndrome patients) have increased risk of developing cancer.

Scientific basis? Long explanation, but you can read up Pathological Basis of Disease 7th edition pg.328 to 331. I have summarized it in my above post and placed in as many "lay-man" terms as i can. :)

On what grounds am I basing my agreement that HIV patients are at higher risk?
On the basic principles of pathology itself and on the core foundations of physiology, immunology and virology. As well as
-National Review of Immunology 1:41, 2001
-New England Journal of Medicine 342:1416, 2000
-National Review of Cancer 2:373, 2002
-Annual Review of Medicine 53:499, 2002
-Robbins and Cotran : Pathological Basis of Diseases, 7th edition

The relationship between immunosuppression and cancer is what every medical student learn as part of their second year syllabus. :)

Akmar, your turn will come soon. :)

J Lee said...

..and Global Observer,

I would like to ask, on what basis do you say that immunosuppression do not lead to an increased risk of cancer? Mind explaining the scientific basis on that? :)

AkMaR said...

To J Lee...

Yes, i'll have to wait for my turn to come but i'm glad now that i have an overview of it.

Btw, mind giving me ur url? As u said the discussion is even more interesting than ur post. Perhaps i can check out that one?