Smoking, cancer, correlation between quitting smoking and increased immediate risk

Question

There is "proof" out there today that suggests smoking is directly linked to cancer. I cannot argue against that, for the evidence in favor appears strong, and the evidence against is lacking. I'll happily sit here and agree that smoking increases the risk of cancer. This question, however, is not about how smoking increases the risk of cancer, rather how stopping smoking might increase the risk of cancer.

Consider what I know so far:

• Cancer is caused by mutant cell growth.
• Mutant cell growth is believed to be caused by chemicals in the smoke
• Smoking itself stunts growth, thus slowing the cell growth rate

If the growth stunt is severe enough that it will reduce the cell growth rate by 20%, one might assume this would take some weeks (let's say 8 weeks, sounds reasonable to me, though I lack knowledge of the subject) to recover. This will likely be some scale and will gradually decrease to somewhere near 0.

Further to this, the risk of cancer is not directly related to the lung, but it is believed to be caused by chemicals entering through the lung into the blood, and travelling around the body, causing cancer in various organs.

Consider that the cell growth is probably linked (in the lung, at least) to chemicals "surrounding" the existing cells, this explains why smokers run short of breath. This partially explains the growth stunt side of smoking. Perhaps this happens body-wide, I don't know.

Then consider what will happen when one stops smoking. The cell growth rate will begin to radically and unexpected increase as the growth stunt is suspended, meanwhile chemicals will still exist in the blood and organs which will be perverting cell growth causing mutant (cancerous) cells. At this point the body is unprepared and settled into its routine of slowly generating cells, but now it is generating them faster and is struggling to keep up. Energy is lacking in areas, and there is further cause of mutant cells to grow and even to be allowed.

Surely, given this reasoning, it might be understandable that stopping smoking increases the immediate risk of cancer, though reducing the long term risk?

Does anybody know, or can anybody find reasonable proof that any part of this argument is flawed? Is there any research to suggest that there is or is not an immediate increased risk? The one thing that people never mention in the side-effects of quitting is the risk of immediate body failure through a variety of means (I've known people to come with flu-like symptoms then find they have cancer weeks later). Is this really unexplored? Or is the nanny state trying to hide it from smokers to prevent them from damaging their health further?

Answer 1

To summarise your argument, cancer is a disease characterised by uncontrolled cell division of mutant cells. Smoking decreases cell division, thereby smoking decreases risk of cancer. Furthermore, stopping smoking increases growth rates, thus there's an immediate rise in risk following smoking cessation.

Cancer is NOT caused by cell division. Smoking does NOT cause cancer by cell division. That's the flaw in your argument. What's happening is that cell division ISN'T being controlled. Let's propose that smoking does indeed stunt normal cell growth. The carcinogens in tar from smoking are still floating around causing mutations in the DNA. Most of DNA doesn't code for very much, but some parts of it codes for genes which control cell division. If these genes mutate then cell division is no longer controlled by these genes and hence there's uncontrolled cell division a.k.a cancer. Once these cells are dividing in an uncontrolled fashion, smoking isn't going to limit their growth. That's because this cancer has developed in the presence of these toxins that limit it's growth and despite this it's still managed to occur.

And then that cell growth stunting may actually be causing cancer to occur. White blood cell function is impaired by smoking, these cells usually target cancerous cells and destroy them. Without being destroyed, there's a higher chance of cancer.

And then I could go further, usually cells grow older and die. Maybe smoking by stunting growth of these cells leads to cells that last longer than they should. These cells accumulate mutations and become cancerous, where else they otherwise would've been recycled.

Smoking however has been linked to improving the symptoms of some diseases. Just not cancer.

Answer 2

One thing is pretty clear and needs not to be debated I think: Smoking is pretty unhealthy and can cause cancer. I see a number of misconceptions here: First you assume, that a slower cell division is something you want to have. Most cell of the adult human body do no divide at all (or only at relatively low rates). Some cells have higher proliferation rates belong to the hematopoietic system, the gut, the mucosas of the body and the skin. These cells need to be able to proliferate in order to fulfill their function. Other cells are dividing to replace cells which went into apoptosis or had to be replaced, but this can not be compared like the growing rates of kids.

Then, cell growth is highly restricted and controlled for good reasons. I did a short search for articles describing slower cell growth by smoking. What I found does not favor the idea that slowed cell growth might be beneficial. This paper for example ("Cigarette Smoke Induces Cellular Senescence"), shows that lung fibroblasts are going into senescence and are not able to do necessary proliferation for lung maintanence.

Then, even if cancer is defined (among other things) to be a fast proliferating, uncontrolled growing mass of cells, its not enough to simply let cells grow, to be able to call them cancer cells. To be able to grow as a cancer cell, the cell needs to change genetically and pick up a number of mutations which allows them to escape the security programs of the body. These are apoptosis and the immune system and its not an easy task. Most cells with the potential to become cancer cells get caught on the way. For the way, how cells become cancer cells, this webpage is pretty interesting.

Stopping to smoke does not cause more problems for you body, it reduces them. The number of dangerous substances delivered to your body is reduced, as is the chance for them to cause harm (lower concentrations). It will take quite a while to get rid of them though, for tar in the lung this can take several years.