Edited by Ryan Jien.
In the early 20th century, smoking was widely accepted among people in society. As a matter of fact, smoking had become so widespread that it was prevalent in many public locations, such as offices, planes, and restaurants. Nevertheless, it’s only in the last few decades that society has fully drawn attention to the numerous negative effects it has on human health. Some health problems caused by smoking include cancer, respiratory issues, cardiovascular diseases, pregnancy complications, and more.
In terms of cancer alone, smoking is one of the biggest causes of deaths. In the United States cigarette usage was calculated to be directly responsible for around 30% of deaths related to cancer every year. Unsurprisingly, as smoking primarily damages our lungs, lung cancer is one of the biggest medical problems smokers face.
There are a number of highly dangerous and toxic chemicals involved in cigarette smoke, as well as a well-known, highly-addictive drug called nicotine. Other chemicals found in smoke include tar, carbon monoxide (CO), oxidizing chemicals, metals and radioactive compounds. Tar is sticky, brown and easily stains teeth, fingernails and lung tissue. It consists of solid particles which are suspended in tobacco smoke. These particles contain certain chemicals, such as cancer causing substances called carcinogens. Carbon monoxide is a hazardous and poisonous gas. It is both odorless and colorless, therefore impossible to be identified by the naked eye. It can easily cause death as carbon monoxide molecules diffuse into our blood cells and replace the oxygen particles and their roles in our bloodstream. For people who smoke occasionally, as carbon monoxide levels continue to increase, it gets harder for oxygen molecules in their bloodstream to function and to be transported to organs all around the body. Oxidizing chemicals on the other hand are extremely reactive chemicals which have functions of damaging heart muscles and blood vessels. These chemicals react with cholesterol, which leads to the build up of fatty material on the walls of arteries. This can potentially lead to heart diseases, strokes and more. Some of the metals included in tobacco and cigarettes include arsenic, beryllium, cadmium, chromium, cobalt, lead and nickel, all of which are cancer-causing and harmful for humans (Better Health Channel, n.d.).
Just by listing a few of these harmful chemicals, we can understand how damaging smoking can be to our physical and mental health. However, what would be the impact of smoking towards medicine and its effectiveness? If a lung cancer patient were to continue smoking during treatment, what would be the effects? 64% of cigarette and tobacco smokers diagnosed with cancer still continue to smoke even after they have been diagnosed. Although many try to quit, it is incredibly difficult due to the effects of nicotine and the drug’s addictiveness.
A recent study by the National Institutes of Health (NIH) investigated the effect of smoking on treatment efficacy and toxicity in patients with cancer specifically. 79 cancer patients who all smoked actively were observed for the analysis. This study found that overall, continuation of smoking has resulted in higher risks of radiation-induced toxicity as well as worse chances of disease-free survival. Patients who continued to smoke along with their radiation therapy also resulted in an increased risk of locoregional recurrence. The association between smoking and EGFR tyrosine kinase inhibitor related treatment in patients with lung cancer has been found to lead to less likely progression-free survival when compared to patients who underwent smoking cessation. Next, in terms of chemotherapy, no statistically significant links were observed that could prove smoking’s negative impacts on treatment efficacy or toxicity specifically. (Bergman, M. et. al., 2022)
The association between smoking and cancer is most common with lung and laryngeal cancer, followed by other head and neck tumors as well as cancer of the upper digestive tract. Current evidence has shown that smoking continuously even after being diagnosed with cancer has huge effects on the overall mortality of several types of cancer, while also increasing risks for both second primary cancer and postoperative complications.
In conclusion, the final analysis highlighted the negative impact of smoking during radiation therapy as well as the negative impact it has on overall treatment efficacy, efficacy of EGFR-TKIs as well as radiation-induced toxicity. Nevertheless, in terms of chemotherapy itself, the evidence is too weak to draw any conclusions with smoking during treatment.
So why does this occur? Why does smoking worsen illness symptoms? Firstly, the toxins and substances in tobacco smoke can cause cellular changes which affect how chemotherapy drugs are metabolized, making them less effective, or in worst case scenarios; more toxic. Patients who continue smoking may have fewer natural killer cells circulating through the body. Polycyclic aromatic hydrocarbons (PAHs) found in tobacco smoke can induce many hepatic cytochrome CYP450 enzymes in the liver, which all have important roles in medication absorption, distribution, metabolism as well as elimination. A certain CYP450 enzyme is known as the CYP1A2 enzyme, there are many medications that act as substrates to this specific enzyme, including, duloxetine, caffeine, clopidogrel, clozapine and many more. Due to this fact, smoking decreases the drug concentration of these medications which also leads to notable decrease in efficacy. Contrary to belief, the interactions with drugs are caused by components of tobacco smoke and not nicotine. As a result, nicotine replacement therapy (NRT) can be done without concerning any changes to how the body reacts to drugs.
Smoking in relation to psychiatric meds such as antipsychotics, antidepressants, hypnotics and anxiolytics generally has been shown to have a negative effect on the efficacy.
In terms of these psychiatric medications, the smoke itself decreases the medication concentration in the bloodstream, therefore, usually more of these drug/medication doses are administered inappropriately, which leads to toxicity in the bloodstream and overdose. In terms of cancer treatment, specifically EGFR tyrosine kinase inhibitors, the efficiency decreases as these inhibitors are ATP mimic agents which bind to ATP binding sites on EGFR tyrosine kinase domains, therefore they limit their activity which play a crucial role in cancer growth. EGFR mutations are modifications in the EGFR gene which increases the responsiveness of cancer cells towards the EGFR tyrosine kinase inhibitors. These mutations are much more common in non-smokers, as a result smoking generally decreases the number of EGFR mutations in lung cancer and patients who continue to smoke are less receptive to these EGFR tyrosine kinase inhibitors.
In conclusion, albeit research has mostly been focused on the effects of smoking on the potency of only two specific types of treatment, EGFR tyrosine kinase inhibitors and psychiatric medicine, it is evident that smoking induces a shocking number of negative factors to our health. The relationship between smoking and the decreased responsiveness to medicine, as well as the increased risk of acquired resistance and shorter progression-free survival, emphasizes the complex interaction between tobacco exposure and treatment outcomes. A wider variety of factors must be included by physicians, such as smoking history, when constructing treatment options for patients and to highlight the cruciality of smoking cessation for optimum health outcomes and benefits.
References:
Better Health Channel. Smoking - effects on your body. Better Health Channel. Retrieved October 9, 2023, from https://www.betterhealth.vic.gov.au/health/healthyliving/smoking-effects-on-your-body
DRUG INTERACTIONS WITH TOBACCO SMOKE. (n.d.). Smoking Cessation Leadership Center. Retrieved December 24, 2023, from https://smokingcessationleadership.ucsf.edu/sites/smokingcessationleadership.ucsf.edu/files/A4%20DI%20TABLE.pdf
Edwards Comprehensive Cancer Center. Smoking and Cancer. Edwards Comprehensive Cancer Center. Retrieved October 9, 2023, from https://edwardsccc.org/cancer-risk-and-prevention/smoking-and-cancer/
Bergman, M. et. al. (2022) Effect of Smoking on Treatment Efficacy and Toxicity in Patients with Cancer: A Systematic Review and Meta-Analysis. (2022, August 25). NCBI. Retrieved December 24, 2023, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9454993/
Kroon, L. A. (2007, September 15). Drug interactions with smoking. PubMed. Retrieved December 24, 2023, from https://pubmed.ncbi.nlm.nih.gov/17823102/
National Institutes of Health. (2019, June 24). Cigarette smoking impairs the response of EGFR-TKIs therapy in lung adenocarcinoma patients by promoting EGFR signaling and epithelial-mesenchymal transition. Cigarette smoking impairs the response of EGFR-TKIs therapy in lung adenocarcinoma patients by promoting EGFR signaling and epithelial-mesenchymal transition. Retrieved December 24, 2023, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4656779/
Sairany, H. (2016, May 16). How Smoking Affects Medications. Pharmacy Times. Retrieved December 24, 2023, from https://www.pharmacytimes.com/view/how-smoking-affects-medications
ScienceDirect. (2023, November 7). Impact of Smoking Status on EGFR-TKI Efficacy for Advanced Non–Small-Cell Lung Cancer in EGFR Mutants. Impact of Smoking Status on EGFR-TKI Efficacy for Advanced Non–Small-Cell Lung Cancer in EGFR Mutants. Retrieved December 24, 2023, from https://www.sciencedirect.com/science/article/pii/S152573041400196X
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