Meditations of an oncology geek

Can smoking cause cancer even after quitting?

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3 April 2011

Akosua Tom of San Diego, California asks:

People hear about my dad’s cancer, and then ask if he smoked – he did, but quit 20 years before the squamous cell carcinoma of his maxillary sinus. Could his smoking have been a contributing factor to his cancer, even two decades after he quit?

I would like to preface this week’s article with a quote from the Emperor of All Maladies (a fantastic read on the history of cancer, by the way):

It remains an astonishing, disturbing fact that in America – a nation where nearly every drug is subjected to rigorous scrutiny as a potential carcinogen, and even the bare hint of a substance’s link to cancer ignites a firestorm of public hysteria and media anxiety-one of the most potent and common carcinogens known to humans can be freely bought and sold at every corner store for a few dollars. – Siddhartha Mukherjee

Hi Akosua,

First, I would like to express my condolences to you and your family. The loss of a parent is tough, and I will begin this discussion with the aside that many people derive guilt from past behaviors such as smoking because it is easy to see tobacco use, and thus tobacco-induced cancer, in both themselves and those around them as an action that is entirely under their control. Although it is easy for many to adopt that viewpoint, it is largely irrational and lacking in purpose. The history of tobacco in American culture is long, complicated, and troubled, and the death of a loved one from a “preventable” illness can leave some with lingering guilt for as long as they live. I do not wish to contribute to this, as one of the premises of this blog is to help alleviate fear and guilt through a better understanding of the disease.

That being said, there is an extraordinarily strong link between tobacco consumption and cancer of the lungs, trachea, sinus, and bladder.

Source: American Cancer Society

Cigarette consumption in the US took off after the Second World War, and by the 1970s, organized anti-smoking campaigns began to be disseminated to the public. In the aftermath of these campaigns, there was a noticeable downturn in tobacco consumption. Cancer of the lungs, trachea and sinus often have about a twenty year lag time from exposure to cancer development, indicated by the peak incidence of lung cancer in the early 1990’s.

The twenty-year lag in cancer development is due to the length of time that it takes for cancer cells to develop the hallmarks of cancer. An individual can be exposed to carcinogens decades before cancer development. Strong carcinogens like tobacco smoke can mutate DNA repair genes in pre-cancerous cells, causing a cascade of future mutations that set in motion the gain of cancer hallmarks.

In science there is no such thing as dogma or absolute truth, only greater levels of certainty. The link between tobacco smoke and cancer has been studied for over half a century, and the evidence in favor of this causation is as strong as any in the history of science. I’m referring to countless large-scale, multi-decade epidemiological studies, all the way down to the mechanisms of tobacco carcinogenesis in isolated cancer cells in petri dishes. Tobacco / cigarette smoke causes cancer.

However, tobacco consumption is likely not the only source of cancer of the sinus, as people who have never smoked can also develop such cancers. As for your dad, it is virtually impossible to know for sure the origins of his cancer. We can speculate forever about the causes of an individual’s cancer, but that neither prevents the condition in others nor gives anyone closure.

The risk of developing tobacco-induced cancers is cumulative over time, meaning that people who smoke for twenty years will have several fold higher chance of developing these cancers than someone who smoked for five. I guess what I am trying to say is: if you know someone who smokes, help them stop. There is a mountain of research on addiction that I will not go into, and I am acutely aware that this is easier said than done, but there are times in life where a little tough love can go a long way.


Written by Ryon

April 2nd, 2011 at 6:53 pm

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