Treatment For Secondary Lung Cancer

The treatment of secondary lung cancer focuses on managing patient symptoms and minimising the spread of cancer throughout the body. This article focuses on giving a comprehensive background on secondary lung cancer and available treatment strategies, which will enable the patient or caregiver to understand the most suitable treatment course available for them in regard to their symptoms.

What is secondary lung cancer?

The origin of secondary lung cancer is primary lung cancer. The cancerous cells from the primary tumour in the lung tend to migrate to other parts of the body and lymph nodes through the lymphatic system or the blood. These migrating cancer cells are called metastases. 

For example, a metastasized secondary tumour from the lung could be seen in breast tissue, but it is still identified as lung cancer, as the site of origin is used to define the type of secondary cancer. The spread of cancer from the lungs is most commonly seen in the breast, bone, bladder, kidney, liver, head, and neck region.²

Causes and Risk Factors

Primary lung cancer is caused due to:

• Repeated exposure to tobacco smoke
• Second-hand smoke inhalation
• Familial history of lung or other types of cancer
• Exposure to cancer-causing chemicals, such as asbestos or radon

As secondary lung cancer develops from primary lung cancer, these factors are also the causes of secondary cancer development. Exposure to radiation in therapy for primary cancers is also a risk factor for the development of secondary tumours.³ 

Symptoms of secondary lung cancer

The symptoms of secondary lung cancer include early symptoms from the start of primary lung cancer as well as new ones such as:

• Persistent cough pattern
• Coughing up phlegm with blood
• Shortness of breath and chest pains
• Repeated chest infections 
• Unexplained weight loss or fatigue 

Fluid build-up between the lungs and chest wall can also be seen, contributing to chest tightness or shortness of breath. 

Diagnosis

Secondary lung cancer can be diagnosed with a combination of tests such as:

• Chest X-ray 
• Computed Axial Tomography scan
• Positron Emission Tomography scan
• PET-CT scan

One might undergo several different types of scans for an accurate diagnosis and staging of cancer before the start of treatment.

Types of treatment

The diagnosis plays a crucial role in planning the treatment for lung cancer. Early diagnosis of primary lung cancer is most commonly treated with a combination of surgical removal of tumours and administration of radiation therapy. Chemotherapy is used when the cancer progresses to an advanced stage. 

In secondary lung cancer, the treatment is care-based to improve patients’ quality of life by managing their symptoms, as the cancer becomes untreatable due to excessive spread to other parts of the body. The kind of primary cancer and treatment given for it, the spread of the cancer, and the patient’s overall health play a role in secondary lung cancer treatment. 

The use of combinational therapy, chemotherapy and radiotherapy, is preferred to obtain a better prognosis in certain cases. Apart from the existing standard of care, there are clinical trials for new drugs and methods aiming to eradicate secondary lung tumours, which is a hopeful start for completely treating secondary cancers.

Chemotherapy

This involves the use of cancer cell-killing drugs to either reduce the growth of the tumour or cure it. Chemotherapy is administered in cycles depending on the type and stage of cancer. 

For secondary lung cancer, chemotherapy is used as maintenance therapy. It is given in hopes to manage the symptoms while enhancing the effects of the first-line treatment to increase the survival rate. The commonly used FDA-approved drugs are Erlotinib and Pemetrexed, showing remarkable rates of survival in patients.⁴ 

Hormone therapy

Certain secondary lung cancers found in parts such as the breast and prostate are dependent on the hormones secreted for their growth. Regulating the levels of hormones can aid in the control of secondary tumour growth. Certain medications are administered orally or as injections to reduce hormone levels. 

Targeted cancer drugs

Targeted cancer drugs are precise treatment methods which focus on the genetic differences between different types of cancer. The drugs tend to target the genes and proteins in cancer cells which are responsible for their growth and spread. 

Currently, many approved targeted therapies are available and they are rapidly developing into clinical trials for many secondary cancers. Some of the most well-known and used targeted therapies are:

• Monoclonal antibodies (MABs)

MABs are drugs that inhibit a particular target inside or outside of the cancer cell. They are small man-made molecules that help chemotherapy drugs reach into the cancer cells for effective killing. Some MABs are classified as immunotherapeutic agents as they contain factors to block the growth factor component in cancer cells.⁵ MABs are considered personalised therapy as they are very specific to treating certain types of cancer. 

• Cancer growth blockers

Cancer growth blockers/inhibitors target the naturally produced growth factors in the body which cause the cancer cells to grow, divide, and spread. It is similar to certain MABs, but cancer growth blockers don't deliver any drugs, instead only focusing on reducing the growth factor's levels in the body, inhibiting the growth factor receptor on cancer cells, and blocking the signals activated by the receptor.⁶

• PARP inhibitors

PARP is a DNA repair regulator which is often deregulated in various types of cancer. PARP inhibitors block the disruption caused by cancer cells to the DNA. Due to its very specific therapeutic target, it is only used for certain types of primary and secondary lung cancers.⁷ 

• Anti-angiogenics

Angiogenesis is the process of tumours creating new blood vessels in their surrounding tissue. This keeps the tumours nourished and gives them the ability to spread cancer cells via those vessels. Anti-angiogenics are small molecule drugs that block the growth of these blood vessels in tumours, causing the tumours to die by depriving them of nutrients.^8,9 

Immunotherapy

Immunotherapy is the use of drugs to activate and enhance the immune system in one’s body to effectively recognise and kill cancerous cells. The human immune system prevents itself from attacking healthy and normal cells by using ‘checkpoints’. Cancer cells disrupt these checkpoints to protect themselves from the immune system and also create uncontrollable cancer cell growth. 

Immunotherapy uses drugs called checkpoint inhibitors which target the checkpoints to block any activity induced by cancer cells while sparing the healthy surrounding cells. Immunotherapy is used as a first-line treatment alongside chemotherapy for certain types of primary cancer.¹⁰

Radiotherapy

Radiotherapy uses X-rays and other forms of radiation to shrink the tumours. It is used on primary tumours to make them more operable and is seen as a palliative treatment in secondary lung cancers. 

Radiotherapy has two types, external and internal. External radiotherapy is administered by a radiographer using a direct radiation beam from the outside focusing on the tumour inside the body. Internal radiotherapy is administered by a doctor using an internal tube-like structure which delivers the radiation directly to the tumour. Internal radiotherapy is very beneficial in lung cancers as it helps to shrink the tumours obstructing the airways, and also prevents any recurring infection and internal bleeding in the tumour.¹¹

Surgery

Surgery is used to remove tumours in primary lung cancer in the early stages, alongside chemotherapy and radiotherapy. Doctors will take into consideration: 

• The location of secondary tumours
• The number and size of the tumours
• The treatment received for the primary lung cancer
• Other health complications that might hinder the surgery

Surgical removal of tumours from the lungs or any part of the body is an intensive process, so doctors will only take this measure if you are in good health. It is always good to know your options, as there are many minimally invasive surgical procedures which can be used to remove multiple tumours in advanced stages. 

Ablation

Ablation is a minimally invasive procedure which involves “burning” or “freezing” tumours using specialised tools. The process is usually only done at certain specialist clinics. With lung cancer, it is proven to help manage symptoms by shrinking tumours that cause blockage and reduce chronic infections in secondary lung cancers. Ablation is delivered in two ways:

• Radiofrequency ablation (RFA)

RFA uses high-energy heat generated from external electric sources directly on the tumours to kill cancer cells. RFA is used on solid tumours that are well accessible from outside and found in the early stages of tumour development. 

• Cryoablation (cryotherapy)

Cryotherapy is the insertion of a needle-like instrument into the tumour where a freezing gas is released to “freeze” the tumour. The tumour is allowed to thaw and is then refrozen a few times to ensure the complete killing of cancer cells. This procedure is beneficial for pain management and is also used when surgery is not possible in secondary lung cancer. 

Symptom control

The above-mentioned treatments will help with symptom management in secondary lung cancer, but there are other methods to tackle those symptoms as well as any smaller symptoms caused.

• Shortness of breath and tightness in the chest is extremely frightening, and may be managed by nebulisers or oxygen therapy
• The fluid buildup between the lungs and the chest can be drained using a tube called a stent to enable better breathing
• Doctors can help you with certain breathing exercises
• Persistent coughs tend to be treated with medicines such as suppressants
•  Some general symptoms, such as tiredness and lack of appetite, can be improved with the help of a clinical oncology dietician

Prevention of Secondary Lung Cancer

Secondary lung cancer can be prevented if the primary lung cancer is detected early on. Therefore it is important to act fast. Some precautionary measures are:

• Genetic testing if your family has a history of lung cancer
• Avoiding tobacco smoking and inhaling secondhand smoke
• Adhering to work safety guidelines when working with cancer-causing chemicals and gases such as arsenic and radon
• Getting a combination therapy for primary lung cancer to avoid recurrence
• Getting routine check-ups as a precaution, even if the doctor says you are completely cancer free

An overall healthy lifestyle and these precautionary measures can significantly reduce the chances of the development of secondary lung tumours.    

Summary 

Secondary lung cancer is the result of already existing primary lung cancer and is incurable. Fortunately, there are many treatment options available to minimise the symptoms. If you or anyone you know is currently experiencing any of the mentioned symptoms, immediately reach out to a medical professional. If you are experiencing secondary lung cancer and want to know if any of the mentioned treatments are a good fit for you, speak to your oncologist to find out more about them.