Cigarette smoking has been shown to be one of the leading causes of preventable deaths worldwide. Smoking may also give rise to different types of cancers, the most common of which is lung cancer. However, it can lead to more than 15 types of cancer in other parts of the body, such as the colon, rectum, oesophagus, stomach, pancreas and others.
So, how does smoking increase the incidence of cancer?
It comes as no surprise that the number of years one spends smoking affects the risk of cancer accordingly. Research has shown that a DNA change occurs for every 15 cigarettes smoked, possibly leading to a malignant transformation of cells.
Chemicals in cigarette smoke enter the bloodstream and affect individuals systemically. Although the human body is capable of dealing with some damage, the amount of harmful agents in tobacco smoke is so disruptive that the body may not even be able to cope with it.
It is interesting to note that:
• 90 per cent and 83 per cent of lung cancers in men and women respectively are caused by smoking;
• nine out of every 10 people who die of lung cancer are smokers; and
• Smoking increases the risk of developing lung cancer by 10 to 15 per cent.
Since smoking is addictive, this is of concern not only as it increases the chances of developing cancer but also because it may have an impact on the treatment of cancer. Radiotherapy is an example of the latter and plays a crucial role in cancer treatment.
In simple terms, this treatment modality delivers high doses of ionising radiation to kill cancer cells, thereby shrinking tumours or slowing their growth by damaging their DNA. Research has shown that approximately 50 per cent of all patients diagnosed with cancer will receive radiotherapy as part of their treatment.
The impact on treatment efficacy
Continuing to smoke throughout radiotherapy may lead to a reduction in the effectiveness of the treatment. This has been observed with several cancers, such as prostate and lung cancer.
Smoking reduces the oxygen concentration present in all cells, including the oxygenation in tumour cells. The therapeutic effect of radiotherapy strongly depends on the amount of oxygen present in order to cause cellular damage in the target.
The long-term risk of dying from cardiovascular disease or lung cancer after radiotherapy may be increased in individuals who continue to smoke
Moreover, smokers have reduced levels of natural-killer-cell (i.e. a crucial component of the immune system) activity in their peripheral blood, which may also contribute to this.
In people with prostate cancer, smokers were 2.3 times more likely to develop distant metastasis within 10 years of radiotherapy than non-smokers. However, this may be influenced by several other confounding factors.
Following radiotherapy, non-smokers have also been reported to survive longer on average compared to individuals who continued to smoke. Furthermore, in animal studies, when tumour cells were exposed to cigarette smoke, accelerated cellular growth was observed.
Therefore, smoking while receiving radiotherapy may result in a reduced response to treatment. This effect may be due to a number of agents in the cigarette smoke, such as nicotine and tobacco.
Impact on radiation-induced side-effects
Smoking while undergoing radiotherapy treatments has been linked to a rise in radiation-induced side effects, both during and following treatment. Such side effects depend on the treatment site and include fatigue, skin reactions and diarrhoea.
Some of these side effects may last for up to six months following completion of treatment. This effect has been studied in several treatment sites, namely lung, pelvic, breast as well as head and neck cancers.
Therefore, the quality of life of smokers may be significantly diminished. In addition, the increase in side effects may also prevent smokers from completing radiotherapy, due to the significant burden they may cause.
Furthermore, the long-term risk of dying from cardiovascular disease or lung cancer after radiotherapy may be increased in individuals who continue to smoke. However, modern radiotherapy techniques are able to reduce the radiation dose to the surrounding healthy tissues, such as the heart and lungs, while better targeting the cancer itself. Although this reduces the risk, the possibility is still present.
Is there an alternative to cigarette smoking?
Although stopping smoking may be a challenge, it is neither impossible nor too late to do so, as long as one sets his or her mind to it. Although some may resort to e-cigarettes (smokeless tobacco or vaping), little is known of the latter’s detrimental effects. These may include lung injury or even forms of cancer in the long run.
There are several reasons why people smoke ‒ some do it just for recreational purposes, others feel they want to vent out and believe smoking will help solve their problems and make them feel less stressed, at least temporarily.
Using nicotine substitutes can help to stop smoking. Healthy alternatives may include exercise and taking up a sport, writing, cooking, listening to music or practising a talent. Not only does this help boost one’s energy levels and mood but it is also a key element in preventing long-term damage to oneself.
Radiotherapy is a well-established treatment for numerous diseases, such as cancer. While smoking may be attributed to the incidence of certain cancers, continuation of smoking while receiving radiotherapy or following treatment may also negatively impact the outcome.
Therefore, smoking should be stopped prior to starting, due to this impact and also due to a number of other health benefits not related to radiotherapy.
Robert Pisani, a final year student reading for a Bachelor of Science (Honours) in radiography, is currently working as a trainee radiographer at the Sir Anthony Mamo Oncology Centre, helping during the COVID-19 pandemic. Amy Xuereb is a second-year radiography student and the Malta Health Students’ Association (MHSA) external affairs officer.
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