Breast Cancer And Smoking

Introduction

Cancer happens when abnormal cells begin to grow uncontrollably and can grow beyond their usual boundaries. They can invade adjoining tissues and organs and/or spread to other distant organs. According to the global cancer incidence, breast cancer ranks at the top, contributing to about 12.5% of the total number of new cases.¹ 

As with most cancers, many factors can influence its growth. Tobacco is one of the modifiable risk factors for breast cancer. This means that it can be changed to positively affect your likelihood of developing breast cancer. Unmodifiable factors also exist such as being born a female and the person’s genetics. Carcinogens and other toxins present in cigarette smoke are believed to cause biological mutations that can favour cancer development and, to a large extent, the outcome of breast cancer treatment.

Let's explore more deeply the effects of smoking on breast cancer.

The relationship between breast cancer and smoking

Research findings

Smoking and its chemical compounds have been studied for decades in relation to various health issues, especially cancer. For many diseases including breast cancer, smoking has been classified as a modifiable risk factor.

 A cohort study done on smoking and the risks of breast cancer concluded that “smoking was associated with modest but significantly increased risk of breast cancer, particularly among women who started smoking at adolescent or peri-menarcheal age”.²  This research suggests that not only is smoking a risk factor for cancer but its initiation, duration and period are important factors to consider in the relationship between smoking and breast cancer.

Researchers also established links between smoking and breast cancer. Here are some important biological mechanisms believed to support the relationship between smoking and breast cancer:

DNA damage

• Chemical compounds found in tobacco smoke like N-nitrosamines, aromatic amines and acetaldehydes can cause long-term damage to cellular DNA
• DNA is a molecule present in your cells that dispenses instructions on how to make proteins responsible for growth, development and overall health; it controls how cells grow and behave
• Smoke inhaled in the lungs travels through the bloodstream and can reach other organs. 
• In the long term, cellular damage can result in genetic damage that can be responsible for cancer growth.³

Inflammation and oxidative stress 

• A mixture of chemicals present in tobacco smoke like nitrogen species among others, induces oxidative reactions and inflammation in the body
• This state of chronic inflammation can contribute to the development and progression of cancer, including breast cancer⁴

Hormonal impact 

• Based on the presence or absence of hormones (estrogen and progesterone) receptors on breast cells, breast cancer can be classified into hormone-receptor positive (ER+ or PR+) or hormone-receptor negative breast cancer
• It was found that smoking is a risk factor for estrogen receptor-positive breast cancer but was statistically insignificant and less clear for estrogen receptor-negative breast cancer

Breast cancer incidence among smokers compared to non-smokers

Although the association between smoking and breast cancer has been controversial with several studies published in the 1990s and 2000s remaining unclear. More recent studies concluded that smoking is a risk factor for breast cancer even though the evidence remains limited. As a matter of fact, more studies need to be done.

A study found that there is a 9% increased risk of breast cancer between former smokers and non-smokers. The same study also found a 19% risk of breast cancer in current smokers.

Another meta-analysis study found that active and passive smokers were at increased risk of breast cancer.⁵

Other risk factors associated with smoking 

The development of breast cancer is a multi-factorial and multi-step process. Alongside smoking, here are some important risk factors for breast cancer:⁶

• A family history of breast cancer
• A previous history of breast cancer
• Heavy alcohol drinking
• First menstrual period at an early age
• Starting menopause at an older age
• Obesity
• Radiation exposure

Effect of smoking on breast cancer prognosis

With smoking being a risk factor for breast cancer, can smoking affect the prognosis of breast cancer after diagnosis? Does smoking affect the response to treatment of breast cancer patients and their survival? Does it affect the recurrence rates of breast cancer in previously diagnosed patients?

Influence on treatment response

Smoking was found to impact the treatment of breast cancer as it impaired wound healing after surgery and can result in many complications such as surgical site infection, skin-flap necrosis and epidermolysis.⁷ In most cases, breast cancer patients require a mastectomy for removal of the tumor and some may require reconstructive surgery following removal of the breast tissues. Patients are often advised to stop smoking a few weeks before undergoing elective surgery.

Smoking can also reduce the effectiveness of radiotherapy treatment for breast cancer patients. It can create a hypoxic environment which limits the effectiveness of radiotherapy.⁸

Impact on survival rates

Smoking has been found to significantly impact the survival rates of patients who smoked before and around the period of diagnosis. The intensity of smoking and the duration affect the survival rates. Overall, survival rates were worse in smokers.⁹ However, quitting smoking was found to improve the survival rates among breast cancer patients who were smokers.¹⁰

Association with recurrence rates

Breast cancer patients who smoked before treatment or were smoking during treatment were found to have higher recurrence rates than breast cancer patients who did not smoke. 

A study published in the National Library of Medicine concluded that there was a dose-dependent recurrence risk increase and poorer prognosis in breast cancer patients who smoked compared to those not exposed to smoking. The results of this study were that; for former smokers of 35 or more pack-years of exposure, the probability for recurrence increased by 37% whereas the probability of recurrence in current smokers was by 41%.¹¹

Public health implications

Being a leading cause of female mortality in the world, breast cancer is considered as a major public health concern. The following are some of the major  public health implications of the impact of smoking on breast cancer:

• The increased burden of the disease with its higher recurrence rate and lower survival rate
• The increased healthcare associated with the management of smoke-related breast cancer complications 
• The poor quality of life of smoking breast cancer patients and survivors 

Awareness campaigns and education

Educating people about the risks of breast cancer is the key to effective disease prevention. Raising awareness and implementing education programs about the links between breast cancer and smoking are key public health strategies.

Here are some basic approaches that can be taken for awareness campaigns and education on the modifiable risk factor of breast cancer, which can reduce a lot of burden on the general population:

• Public service announcements
• Healthcare providers education
• School-based education
• Social media campaigns

Smoking cessation programs for breast cancer patients

Offering smoking cessation programs for at-risk patients on their journey to potentially developing breast cancer is of utmost importance. Educating and encouraging them to cease smoking will have a profound impact on their overall care and survivorship.

Providing a personalised approach and behavioural counselling takes into consideration the patient’s needs and personal preferences for cessation methods, which can greatly improve the outcome of the patients. For example, one patient might prefer group counselling while another favours one-on-one counselling. Catering to their preferences in this way will greatly aid in their willingness to participate. 

Creating a supportive environment around the patient can also be very beneficial. This can even increase their liability for treatment. Two methods for this are:

• Encouraging and motivating the patient by connecting with former smokers who have successfully quit
• Letting them participate in peer support groups by involving family members or caregivers

Policy implications and regulation

Effective policies and regulation implementation can play an important role in addressing the link between breast cancer and smoking. It can reduce breast cancer incidence and mortality as it educates people about the dangers of smoking and also actively discourages people from initiating or continuing smoking.

This can be achieved through tobacco taxation, the implementation of tobacco-free laws and the restriction of advertisements.

Summary

• Breast cancer is a major cause of female cancer mortality in the world
• Many factors play an important role in its occurrence; some are unmodifiable like being born a female and the person’s genetics. Others are modifiable and can improve or worsen the management and outcome of the disease like smoking
• The relationship between breast cancer and smoking is complex and many-sided. It was thought that breast cancer and smoking were unrelated but researchers can now prove a potential connection between the two
• Encouraging smoking cessation and prevention can greatly influence the effects of breast cancer treatment and improve the survival rates of these patients
• Breast cancer remains a major public health concern and its management should involve multiple actors, organisations and programs
• This includes health awareness and education programs, policy implementation and regulation and encouraging more scientific research to elaborate more fruitful prevention and treatment plans. 
• Eventually, efforts will improve the outcomes and lift the burden of this challenging disease on individuals, families and the healthcare system