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What is Adenocarcinoma of the Lung: Causes, Symptoms, Diagnosis, and Treatment

Definition and Overview

Adenocarcinoma of the lung is a type of lung cancer. It occurs when certain DNA mutations cause abnormal cells to multiply and tumours to grow. Just like other types of lung cancers, adenocarcinoma commonly affects people who smoke or are exposed to secondhand smoke.

The disease accounts for about 40% of all lung cancer cases. It is more common in women than men and is more likely to occur in people below 45 years old. In general, it tends to grow slowly and is often found before it spreads to other organs.

When caught during early, the prognosis for lung cancer is generally good. Cancer contained in the lungs (localised cancer) can be totally removed with surgery. However, when cancer cells spread to the lymph nodes, bones, or brain, the patient’s chances of cure become very low. This remains the case even if they undergo all forms of cancer treatment.

Causes of Condition

The exact reason why lung cancer occurs in some people is not fully understood. However, the disease is linked to many risk factors, such as:

  • Smoking - According to statistics, up to 90% of all lung cancer cases are caused by smoking

  • Exposure to secondhand smoke

  • Exposure to asbestos and radon gas

  • Exposure to other carcinogens, such as air pollution

It is important to note that not every person who has risk factors develop lung cancer. Many who have smoked for years remain cancer-free. It goes the same way for those who do not have risk factors. Sometimes, people who have never smoked in their lives suffer from the disease. Various research and studies are being conducted to understand what causes this. But to be safe, experts advise people, regardless if they have risk factors or not, to consult their doctor right away when they develop symptoms listed below.

Key Symptoms

Early stages of lung cancer may or may not cause symptoms. The earliest signs are a cough that does not go away with treatment, wheezing, and coughing blood. Others include:

  • Breathing problems

  • Chest pain

  • Fever

  • Trouble swallowing

  • Poor appetite

  • Weight loss

If cancer spreads to other parts of the body, it can cause other symptoms, such as:

  • Headaches and seizures, if cancer spreads to the brain

  • Bone pain and fractures, if cancer spreads to the bone

  • Jaundice and upper abdominal pain, if cancer spreads to the liver

Who to See and Types of Treatments Available

Patients with symptoms listed above can consult a general practitioner or family doctor for initial assessment. Patients suspected of lung cancer are referred to an oncologist (cancer specialist), who would normally order a chest x-ray right away. This is an imaging test that uses small amounts of radiation to produce pictures of the lungs.

A chest x-ray is followed by other more sensitive imaging tests if it finds an abnormal growth in the lung. These tests can confirm whether or not cancer cells have spread to other parts of the body. They can also provide important details that can affect the patient’s treatment plan.

  • Computed tomography (CT) scan

  • Magnetic resonance imaging (MRI) scan

  • Positron emission tomography (PET) scan

  • Bone scan

Doctors will also get a small sample of lung tissue for further testing or analysis. This can be performed by

  • Passing a thin, flexible tube into the nose or mouth (bronchoscopy)

  • Inserting a special needle in the chest (needle biopsy)

  • Open biopsy

Once a lung cancer diagnosis is confirmed, the doctor will proceed by determining its stage. Cancer staging determines whether or not cancer has already spread to other parts of the body.

  • Stage 1 - The cancer is contained in the lung

  • Stage 2 - The cancer has spread to the lining of the lungs and nearby lymph nodes

  • Stage 3 - The cancer has reached surrounding tissues

  • Stage 4 - The cancer has spread to other parts of the body, such as the bone, liver, or brain

Treatment

The best scenario in lung cancer treatment is removing the entire abnormal growth through surgery. This is possible in small tumours or early-stage cancer. This is often followed by chemotherapy that can kill any remaining cancer cells in the body.

Sometimes, removing the entire tumour is not possible because of its location or the patient is too ill to undergo surgery. If this is the case, chemotherapy and radiotherapy can be performed separately or combined to shrink the tumour or stop it from growing. These therapies can also treat the symptoms of the disease.

Other treatment options include:

  • Immunotherapy - Strengthens the patient’s own immune system so it can fight cancer cells.

  • Targeted therapy - Uses medications designed to attack DNA abnormalities that caused the disease.

It is important for patients to understand that even when their treatment is deemed successful, the disease can come back in the future (recurrence). Because of this, they are advised to follow-up with their doctor and undergo testing on a regular basis. The goal is to catch early signs of recurrence so that treatment can be started right away.

Prognosis

The prognosis for lung cancer depends on its stage and how soon a patient received treatment. If the abnormal growth is totally removed with surgery, the outlook is very promising. However, the five-year survival rate for patients whose disease has reached advanced stages can be as low as 18%.

References:

  • DiBardino, D.; Saqi, A.; Elvin, J.; et al. “ Yield and Clinical Utility of Next-Generation Sequencing in Selected Patients With Lung Adenocarcinoma.”Clinical Lung Cancer. 2016; 17(6):517-522.e3.

  • Dacic, S. “Molecular genetic testing for lung adenocarcinomas: a practical approach to clinically relevant mutations and translocations.” Journal of Clinical Pathology. 2013; 66(10):870-874.