Secondary Lung Cancer

Cancer is an umbrella term for a range of conditions where mutated cells in a specific part of the body divide uncontrollably and do not die as normal. These cancerous cells can cause broader problems by invading, damaging, and destroying surrounding healthy tissue. Cancer cells can spread to other healthy tissues around the body – this process is called metastasis. Cells from the primary cancer site can break away and travel, via the bloodstream or lymphatic system, to new sites, such as the lung, and form secondary cancers (metastases) made of the same cell type as the primary tumour. Secondary lung cancer is cancer that has spread to the lungs from elsewhere in the body. Symptomatically it resembles primary lung cancer but biologically it can be quite distinct as the cells originate from the primary site in primary lung cancer – for example, if bowel cancer spreads to the lungs, it is still considered bowel cancer (along with secondary lung cancer).

What is Lung Cancer?

Lung cancer is five or more different types of cancer, divided into two groups, that all affect the lungs.¹ The two groups are: small cell lung cancers (SCLC) and non-small lung cancers (NSCLC). SCLC account for 15-20% of lung cancers and spread to other tissues early in the course of the disease. NSCLC account for 80-85% of lung cancers.² The treatment given to a patient is determined by the type of cancer they are diagnosed with.

There are three main types of lung cancer: adenocarcinoma, squamous cell carcinomas and large cell lung carcinomas. Adenocarcinoma is the most common and starts in the mucus-secreting gland cells in the lining of the airways. Squamous cell carcinomas originate in the flat cells that line the airways.  Large cell lung carcinomas are characterised by large round cells when viewed under a microscope.

There are other rarer cancer types that affect the lungs and are neither SCLC or NSCLC, including lung lymphoma and sarcoma. Another type is mesothelioma which is a rare type that originates in the pleura – the membranes which cover and protect the lungs. 

The chances of lung cancer spreading to other parts of the body are high because symptoms of primary lung cancer often go unnoticed for some time and some lung cancer types metastasise very quickly, often to the bone or the brain. 

Risk Factors

The main risk factors for primary lung cancer are:

• Age – 66% of lung cancers are diagnosed in people over 65³
• Genetics – a non-smoker with an immediate family history of lung cancer may be more prone to develop the disease
• Smoking – primary or second-hand smoking is widely believed to be the leading cause of lung cancer, accounting for more than 70% of cases⁴
• Exposure to asbestos or other carcinogenic pollutants (especially if you smoke)
• Exposure to radon – radon is a colourless, odourless radioactive gas that is found in some houses at high levels

What is Secondary Lung Cancer?

Secondary lung cancer is cancer that has spread from a primary site elsewhere in the body, including:

• Breast cancer
• Bowel cancer
• Kidney cancer
• Testicular cancer
• Bladder cancer
• Melanoma skin cancer
• Bone cancer
• Soft tissue sarcomas
• Head and neck cancer

The secondary cancer is of the same cell type as the primary cancer and is not SCLC or NSCLC. The biggest risk factor for secondary lung cancer is smoking: the amount and rate at which you smoke may increase your chances of lung cancer, so heavy smokers are at a higher risk.

Symptoms and Diagnosis of Secondary Lung Cancer

Some of the symptoms of secondary lung cancer may already be present due to the primary cancer, and they include:

• A persistent cough
• Having a change in a cough you have had for a long time
• Shortness of breath
• Ongoing chest infections
• Unexplained weight loss or loss of appetite
• Coughing up blood or bloody phlegm
• Chest pain or an ache or pain in the chest or shoulder
• Feeling tired all the time (fatigue)
• Pleural effusion

Pleural effusion is a build-up of fluid between the lung and the chest wall, caused by inflammation in the pleura, stopping the lungs from expanding fully. This can cause shortness of breath, pain and discomfort.  

These symptoms can also all be caused by other non-cancer-related causes, hence medical advice should be sought if they appear.

Tests for Secondary Lung Cancer

There are several different tests to diagnose secondary lung cancer:

• Chest X-ray
• CT scan (Computed Axial Tomography, a type of X-ray that makes 3D pictures)
• PET scan (Positron Emission Tomography, scans for a mildly radioactive substance introduced into the body to make 3D pictures)
• PET-CT scan

Treating Secondary Lung Cancer

Primary lung cancer treatment depends on the type of cancer mutation, how far it has spread (the stage) and how good the patient’s general health is. If the cancer is diagnosed early enough, surgery or radiotherapy to remove the tumour is possible. If the cancer is too advanced for these to be successful, chemotherapy is usually used.

Secondary lung cancer are usually incurable, but there are treatments available to minimise the problems it causes:^5,6,7

• Chemotherapy (using cytotoxic drugs to kill the cancer cells)
• Hormone therapy (mainly to treat prostate and breast cancer metastases)
• Immunotherapy (stimulating the immune system to attack the cancer cells)
• Radiotherapy (to destroy the cancer cells)
• Surgery (to remove the cancerous tissue)
• Tumour ablation (using heat or cold to destroy cancer cells)

Prognosis

Lung cancer usually does not cause noticeable symptoms until it is very advanced in its spread through the body. This means the outlook for the disease is not as good as many other types of cancer. The individual prognosis depends on many factors including: whether the cancer has spread to more than one part of the body, how quickly it is growing, and how it responds to treatment.  It is usually difficult to predict. Secondary lung cancer is a sign of widespread cancer with a poor survival rate.

Living more than 5 years with metastatic cancer in the lungs is rare. Sometimes patients with certain types of cancer that have only spread a limited amount to the lung can be cured with surgery (sarcoma, renal cell carcinoma, bladder cancer, colon cancer, or melanoma) or chemotherapy (lymphoma or testicular cancer).

Summary

Secondary lung cancer is a cancer that originates and spreads from a site other than the lungs into the lungs, differing it from (primary) lung cancer which originates from lungs directly. As this disease is usually incurable, regular checkups to ensure sufficient health condition are important. If you experience or know anyone experiencing the aforementioned symptoms listed in this article, please contact your GP or visit the nearest clinic or hospital to undergo the necessary tests.

Frequently Asked Questions (FAQs)

Q: How long can you survive secondary lung cancer?

A: Living more than 5 years after diagnosis is rare.

Q: How is secondary lung cancer treated?

A: This depends on the nature of the primary tumour and your general health, as well as your preferences.  Treatments include chemotherapy, hormone therapy and tumour ablation.

Q: Can you survive lung cancer that has spread?

A: The 5-year survival rate for metastatic NSCLC is about 7%. If the cancer only spreads to nearby tissue, the rate improves to 35%. People with localised lung cancer, which has not spread at all, have a 63% survival rate.  According to the American Cancer Society, the 5-year survival rate for metastasized SCLC is about 3%. The rate improves to 16% if it only has spread locally and to 27% if it has not spread at all.⁸

Q: Can you recover from secondary lung cancer? 

A: Secondary cancer can't usually be cured. Treatment can control it for some time and help prevent further problems from developing.

Q: Can you have surgery for secondary lung cancer?

A: Surgical removal of the tumour is a recognised treatment for secondary lung cancer that started in the bowel, bone or soft tissue. It is not usually suitable for other types of cancer.  Surgery is not usually an option if your cancer has spread anywhere else in your body.

Q: Where does secondary lung cancer spread to?

A: Primary cancer, once metastatic, can spread into a range of tissues.  Any spreading of the secondary tumours is still considered to be metastasis of the primary tumour.  Primary lung cancer spreads predominantly to the brain and bone, but this may not be true of secondary lung cancer.