The Link Between Smoking And The Development Of Head And Neck Cancer

Understanding head and neck cancer 

Head and neck cancer is the sixth most common type of cancer.¹ There are 350,000 cancer deaths and 650,000 new cases of head and neck cancer each year.

Most head and neck cancers are squamous cell carcinoma, which develops in the skin, lining of the mouth, throat, voice box, sinuses, and nasal cavity. These cancers affect the areas involved in breathing, speaking, and swallowing, making early detection and treatment crucial. They usually develop as a result of long-term use of toxic substances like alcohol and tobacco smoke. In some cases, a virus called human papillomavirus (HPV) has also been linked to the development of these cancers.¹

The combined use of alcohol and tobacco increases the risk of head and neck cancers², with both substances together being responsible for 75% of all squamous cell carcinoma of the head and neck (SCCHN) cases. Even in people who don’t smoke, heavy alcohol consumption (three or more drinks per day) has been shown to significantly raise the risk of developing SCCHN.³ This strong link shows the importance of smoking cessation and limiting alcohol intake as key steps in preventing head and neck cancer.

How are they classified? 

Head and neck cancers are classified based on their location, cell type, and stage. Here’s how they are categorised.⁴

By location:

These cancers are named based on where they start in the head and neck:

• Oral cavity cancer – Affects the lips, tongue, gums, and inside of the mouth
  Laryngeal cancer – Develops in the voice box (larynx)
  Pharyngeal cancer – Found in the throat (pharynx), which includes:
  • Nasopharynx (upper part of the throat behind the nose)
  • Oropharynx (middle part, including the tonsils and base of the tongue)
  • Hypopharynx (lower part of the throat, near the voice box)
• Other cancers – Can occur in the salivary glands, sinuses, or nasal cavity

By cell type:

• Squamous Cell Carcinoma (HNSCC): The most common type, forming in the thin, flat cells that line the surfaces of the head and neck
• Other types: Less common types include adenocarcinomas (from the salivary glands) and mesenchymal tumors (affecting soft tissues and sinuses)

By stage (TNM System):

Doctors use the TNM system to determine how advanced the cancer is:

• T (Tumour): Measures the size and spread of the original tumour
• N (Nodes): Checks if the cancer has spread to nearby lymph nodes
• M (Metastasis): Determines if the cancer has spread to other body parts

What is the role of smoking in head and neck cancer?

Tobacco and alcohol use are the two greatest risk factors for head and neck cancers, especially those affecting the mouth, lower throat (hypopharynx), and voice box. This includes all forms of tobacco — smoking, secondhand smoke, and smokeless tobacco like chewing tobacco or snuff.^5,6

People who use both tobacco and alcohol have a much higher risk of developing these cancers than those who use just one. Most squamous cell cancers of the mouth and voice box are directly linked to the combined use of tobacco and alcohol.⁷

Tobacco use is thought to be responsible for:⁸

• 64% of laryngeal cancers (voice box)
• 37% of pharyngeal cancers (throat)
• 25% of nasopharyngeal cancers (upper part of the throat behind the nose)
• 17% of oral cancers (mouth)

Possible mechanisms of tobacco-induced cancer

Tobacco smoke affects the body in many harmful ways, especially at the cellular and genetic level, contributing to the development and growth of cancers — including head and neck cancer (HNC). Here are some of the key mechanisms:

1. DNA damage

Tobacco smoke contains carcinogens that directly damage the DNA in cells, including the genes responsible for repairing cell damage and protecting against cancer. When these protective mechanisms fail, damaged cells undergo uncontrollable growth and form cancer.⁹

Simplistically, tobacco causes DNA damage. When cells try to copy the damaged DNA, mistakes (misreplications) happen, leading to harmful mutations. Over time, this can trigger the body’s internal (endogenous) processes to create even more mutations. These ongoing changes in the DNA can push normal cells to turn cancerous, especially in sensitive areas.

2. Tumour progression

Cigarette smoke doesn't just cause cancer but it can also help tumours grow. It can alter nearby healthy cells, making the environment around cancer cells more supportive of tumour growth and invasion.¹⁰

3. Immunosuppressive effect

It can also weaken the immune system, especially in patients with squamous cell type. It can block the activity of cytotoxic T-cells, the immune cells that usually help destroy cancer, making it easier for tumours to grow unchecked.¹¹

4. Inflammation

Tobacco smoke can trigger chronic inflammation, a process where the body's immune response becomes overactive. This chronic inflammation can create a microenvironment that favours cancer cell proliferation, survival, and metastasis.¹²

5. Mutational signatures

Exposure to tobacco leaves behind a distinct pattern of DNA mutations in cancer cells. These “mutational signatures” are like fingerprints showing how tobacco has shaped the genetic changes in head and neck cancers over time.¹³

What are the symptoms of head and neck cancer?

Head and neck cancer can present themselves in various ways, depending on where it starts. It’s important to pay attention to early warning signs, especially if they persist over a few weeks. Here are some common symptoms to watch out for:¹⁴

• A lump or swelling on the back of the neck, jaw, or inside the mouth
• A mouth ulcer or sore that doesn’t heal
• Pain, numbness, or weakness in the face
• Persistent neck pain
• Difficulty moving the jaw or opening the mouth fully
• Trouble swallowing (also called dysphagia)
• Changes in speech or slurred speech
• Ear pain or hearing loss not related to an infection
• Breathing difficulties or noisy breathing
• Chronic sore throat that doesn’t go away
• White or red patches in the mouth or throat
• Unexplained
• Other signs such as fatigue, bad breath, or bleeding in the mouth or nose

How is it diagnosed?

Diagnosing head and neck cancer starts with understanding the symptoms and performing a thorough physical examination.^15-17

1. Initial assessment and physical exam

During a physical exam, the doctor will check the common symptoms of mouth, neck, and jaw for unusual lumps or swelling. In some cases, an endoscope, a thin tube with a camera, may be used to view hard-to-see areas like the nose, throat, or voice box.

2. Diagnostic tests

To confirm the diagnosis, doctors may order a variety of tests:

• CT Scan 
• MRI Scan 
• PET Scan
• Ultrasound and X-rays 

The most important step is a biopsy, where a small tissue sample is taken and examined under a microscope to check for cancer cells. Biopsies can be done using tools like a laryngoscope, nasal endoscope, or fine needle aspiration for lumps.

3. Other important tests

• HPV Testing – Especially for throat cancers, as some are linked to the HPV
• Genomic Testing – Checks for gene mutations in cancer cells that might guide treatment options

What are the treatment options?

Treatment for head and neck cancer can involve surgery, radiation therapy, chemotherapy, targeted therapy, immunotherapy, or a combination of these, depending on the cancer's location, stage, and the patient's overall health.¹⁸

Surgery

The main goal of surgery is to remove the tumor along with some nearby healthy tissue to make sure all the cancer is gone.

• Small cancers may be removed with simple or laser surgeries
• Larger cancers may need more extensive surgery, followed by reconstructive surgery to restore appearance and function
• Neck dissection may be done if doctors suspect the cancer has spread to the lymph nodes in the neck

Radiation therapy

This treatment uses high-energy X-rays to kill cancer cells or shrink tumours.

• The most common type is external beam radiation
• It can be used alone for small tumours or combined with surgery or chemotherapy for more advanced cases

Chemotherapy

Chemotherapy uses strong medicines to kill cancer cells.

• It can be given before or after surgery or radiation to make those treatments more effective
• Sometimes, it’s used together with radiation (chemoradiation) as the main treatment, especially for advanced cancers

Targeted therapy

These treatments target specific proteins in cancer cells. Like cetuximab, which blocks signals that help cancer grow.

Immunotherapy

This newer approach helps the body’s immune system fight the cancer. Medicines like pembrolizumab and nivolumab are used for cancers that are advanced or have returned.

Supportive care

A team of specialists usually works together, including surgeons, oncologists, radiologists, and rehab experts.

• Speech and swallowing therapy can help patients recover after treatment
• The treatment plan is always tailored to each patient’s needs

Prevention and public health measures 

Controlling the disease is the aim of treatment for head and neck cancers. Here are ways to prevent deadly head and neck cancer.^4,15-18

• Tobacco use: Quit all forms of tobacco and support tobacco cessation programs
• Alcohol consumption: Limit or avoid alcohol to reduce cancer risk
• HPV vaccination: Promote vaccination (Gardasil 9) for individuals aged 9-45 to prevent HPV-related cancers
• Healthy lifestyle: Encourage a balanced diet, good oral hygiene, sun protection, and safe sex practices
• Environmental factors: Minimise exposure to carcinogens, wear protective gear, and ensure proper ventilation
• Screening: Promote regular dental checkups and early detection of cancer
• Public health measures: Raise awareness, support healthy behaviors, ensure access to care, address health disparities, and fund research

Summary

In conclusion, alcohol and tobacco use are major contributors to head and neck cancer, which continues to be a serious public health concern. To lower the incidence of these cancers, preventative measures like quitting smoking, consuming less alcohol, and getting vaccinated against HPV are essential. Affected people's outcomes are improved by early detection, prompt diagnosis, and advancements in treatment, such as surgery, radiation, chemotherapy, and immunotherapy. In addition to ensuring access to care, encouraging healthy habits, and increasing awareness, public health initiatives should support continued research to prevent and treat head and neck cancers. These initiatives have the potential to lessen the disease's worldwide burden.