What is Lung Adenocarcinoma?
Lung adenocarcinoma is the most commonly seen type of lung cancer in the United States. It is a part of the non-small cell lung cancer (NSCLC) group and is closely related to a history of smoking. Even though the occurrence and death rate of this disease have dropped, it is still the top cause of cancer-related deaths in the United States.
Usually, lung adenocarcinoma develops from the glands in the lung lining, and makes up about 40% of all lung cancers. It is the most common type found in people who have never smoked. Lung adenocarcinoma generally happens on the outer parts of the lung. Often, it may be found in scar tissue or areas with long-term inflammation.
What Causes Lung Adenocarcinoma?
The biggest risk factor for all types of lung cancer, including a type called adenocarcinoma, is smoking tobacco. The reason for this is that tobacco smoke contains many harmful substances called carcinogens. Both firsthand and secondhand smoke can increase your risk, and the more you’re exposed to it, the higher your risk becomes.
There are other factors that can also increase your risk of lung cancer. These include having a family member who has had lung cancer, or having a job in which you’re exposed to harmful substances. These harmful substances might include silica (a type of sand), asbestos (a mineral used in insulation), radon (a radioactive gas), heavy metals like lead, and fumes from diesel fuel. However, these factors are less common.
The changes in the p53 gene are often found in cases of non-small cell lung cancer (which is the most common type of lung cancer). These genetic changes can cause the cells to turn into cancer. This happens in about 52% of non-small cell lung cancer cases.
Risk Factors and Frequency for Lung Adenocarcinoma
Lung and bronchial cancers remain a significant health issue, with over 221,200 new cases and more than 158,000 deaths recorded in 2015. These types of cancers are the leading cause of cancer death. They’re also prevalent worldwide, and survival rates remain low, despite improvements in treatment. In fact, the 5-year survival rate is only between 12% to 15%.
In the last 40 years, there’s been a noticeable rise in lung adenocarcinoma, particularly among women, likely due to smoking. The average age of diagnosis for this type of cancer is 71, and it’s very uncommon in people under 20. Recently, adenocarcinoma has become the most prevalent type of non-small cell lung cancer, replacing squamous cell cancer.
- Over 221,200 new cases of lung and bronchial cancers were recorded in 2015.
- More than 158,000 deaths were also reported that year, making these diseases the leading cause of cancer death.
- Globally, lung cancer is widespread.
- The 5-year survival rate is between 12% to 15%, underscoring the seriousness of these cancers.
- The past 40 years has seen a rise in lung adenocarcinoma, especially among women, likely linked to smoking.
- Typically, lung adenocarcinoma is diagnosed at an average age of 71.
- This cancer is very rare before the age of 20.
- Adenocarcinoma has replaced squamous cell cancer as the main non-small cell lung cancer type in recent decades.
Signs and Symptoms of Lung Adenocarcinoma
Lung cancer symptoms and physical signs depend on the stage of the disease. Often, the early stages might show no symptoms at all. Doctors might discover lung nodules accidentally while examining radiographic images for other diseases. As the disease progresses, patients may experience various symptoms like persistent coughing, coughing up blood, and unintentional weight loss. Patients may also suffer from shortness of breath and decreased breath sounds if they have a fluid accumulation around the lungs, known as a pleural effusion. Most patients with lung cancer have a history of smoking and could potentially have related respiratory diseases like chronic obstructive pulmonary disease (COPD), or a family history of lung cancer.
Note that a significant number of patients with lung adenocarcinoma, a specific type of lung cancer, will present with symptoms resulting from local or regional spread of cancer. These symptoms may include:
- Obstruction of the superior vena cava, a large vein that carries blood from the body back to the heart
- Phrenic nerve palsy, which affects a nerve that is critical for lung function
- Horner syndrome, which affects the nerves to an eye and part of the face
- Compression of the brachial plexus, a group of nerves that extend from the spinal cord to the hand
- Pericardial effusion, accumulation of fluid around the heart
On rare occasions, lung adenocarcinoma can cause paraneoplastic syndromes, a group of symptoms that result from substances circulating in the bloodstream produced by the tumor. These can include:
- Cushing syndrome, characterized by weight gain and skin changes
- Eaton Lambert syndrome, which can lead to muscle weakness
- Hypercalcemia, high calcium levels in the blood
- SIADH (Syndrome of inappropriate antidiuretic hormone), leading to low blood sodium levels
- Hypertrophic osteoarthropathy, causing swelling and pain in the joints
Testing for Lung Adenocarcinoma
Smokers or former smokers who smoked heavily are strongly urged by health experts to get regular health checks using a low-dose CT scan. This process, recommended by the US Preventative Services Task Force, is aimed at detecting any potential health problems early.
If a small growth, known as a lung nodule, is found in the lungs, the next steps will depend on what it looks like on the scan. If it looks like it could possibly be lung cancer, a PET/CT (one type of imaging test) could then be conducted, and a biopsy or surgical removal might be needed next.
Based on guidelines by the National Comprehensive Cancer Network, other necessary next steps can include a detailed CT scan of the chest and abdomen (including the adrenal glands) with a contrast dye, examination of the bronchial tubes and lymph nodes in the chest, and checking of complete blood count and blood chemistry profile.
If the lung issue is considered to be Stage II, III, or IV, a brain MRI is suggested to check if the cancer has spread to other parts of the body. After these tests, a clinical stage will be assigned to determine the best treatment approach.
If the doctors suspect that cancer has spread to the bones, a bone scan will be done. On the other hand, PET scans are commonly used to check for the potential return of the disease.
Examining a patient’s sputum, or coughed-up mucus, is typically not helpful as most lung adenocarcinomas (a type of cancer) occur in the outer parts of the lungs.
If an abnormal fluid buildup called “effusion” is noticed, a procedure called needle thoracentesis will be done. It helps in both diagnosing the problem and relieving symptoms by removing some of the fluid.
If a person is being considered for surgical lung removal, pulmonary function testing is conducted to determine if their remaining lung function would be adequate after the surgery.
If the CT scan shows unusual lymph nodes, a mediastinoscopy or thoracoscopy is suggested to evaluate the patient’s stage of disease. Determining the stage of the patient’s condition is vital before any treatment can be recommended.
Treatment Options for Lung Adenocarcinoma
In early stages of cancer (Stage I/II/IIIA), the cancer is either limited in its invasive growth or has only affected a few nearby lymph nodes. Doctors will consider whether it can be surgically removed. If it is operable, they will generally recommend surgery, which will include sampling the lymph nodes to see if the cancer has spread. If surgery is not an option, definitive radiotherapy (a type of treatment that uses high-energy rays, like X-rays, to kill or shrink cancer cells) with the possible addition of chemotherapy (drugs designed to treat cancer) may be used instead. This would be especially true if the cancer has spread to the lymph nodes or if the patient has a high risk of the cancer spreading. There are some specific types of invasive cancer that may be treated with a combination of chemotherapy and radiotherapy before surgery.
The later stages of cancer (Stage IIIB and Stage IV) involve more advanced conditions. This includes the cancer spreading to the area between the lungs (mediastinum), below the windpipe before it splits into left and right (subcarinal), and the nodes on the opposite side of the original cancer site (contralateral nodes), and also includes spread to distant sites (metastatic disease). These stages are typically not suitable for surgery and so they are usually treated with a combination of chemotherapy and radiotherapy. Certain types of cancer that have spread outside of the lungs and don’t cause symptoms may also be treated.
It’s common for doctors to test the cancerous tissues obtained during surgery or biopsy for specific types of genetic changes. Some cancers have changes in the genes EGFR or ALK. If the cancer has these genetic changes, it can be treated with medicines that specifically target those changes – these are called tyrosine kinase inhibitors for EGFR and ALK inhibitors for ALK mutations. However, if the cancer doesn’t show these gene changes, doctors usually recommend a mix of chemotherapy drugs for treatment. This often involves a platinum-based drug, and sometimes an additional drug called bevacizumab.
After treatment, doctors will perform regular checks. These include CT scans of the chest every six to 12 months for two years and annual low-dose CT scans. Patients who have not been fully cured by the treatment may need more frequent checks. In cases where the cancer comes back in the same area or nearby, there might be different treatment options available. These options could include radiation therapy, surgery, chemotherapy, and a light-based treatment called photodynamic therapy. The choice would depend upon where the cancer has recurred and what symptoms the patient is having.
What else can Lung Adenocarcinoma be?
When doctors examine lung problems, they could be considering various conditions that may show certain signs. These can include:
- Benign lung lesions (non-cancerous spots on the lung)
- Granulomas (small areas of inflammation)
- Hamartoma (a benign tumour made up of an unusual mixture of tissues)
- Metastatic lesion (an area where cancer has spread from another part of the body)
- Pneumonia (lung infection)
These possibilities are evaluated through various tests to make a correct diagnosis.
Surgical Treatment of Lung Adenocarcinoma
Patients with stage I, II or IIIA lung adenocarcinoma, a type of lung cancer, usually undergo surgery as part of their treatment. The typical surgical procedures include lobectomy, where a section of the lung is removed, or a pneumonectomy, where the entire lung is removed.
However, it’s important to know that these patients are at a high risk of the cancer returning, or relapsing. So, to lower this risk, chemotherapy, which is a drug treatment that kills cancer cells, usually follows surgery. This is now seen as the standard care procedure.
Possible Complications When Diagnosed with Lung Adenocarcinoma
The complications that can occur after a surgery often include:
- Air escaping from the lungs and accumulating in the chest cavity
- Pain
- An abnormal shape or appearance of the chest
- Failure of the respiratory system, which may lead to death
- Damage to the phrenic nerve, which controls the diaphragm (the main muscle of breathing)
In the case of chemotherapy, complications can involve:
- Pancytopenia, or a significant reduction in the red cells, white cells, and platelets in the blood
- Infections
- Hyponatremia, or a dangerously low level of sodium in the body
- Renal failure, or the kidneys no longer being able to properly filter waste products from the blood
- Peripheral neuropathy, or damage to the peripheral nervous system, leading to weakness, numbness, and pain, usually in the hands and feet
Recovery from Lung Adenocarcinoma
Patients who have had a thoracotomy, which is a surgical procedure to open up the chest, will need intense care for their lungs. This care includes using a device known as an incentive spirometer to help them breathe more deeply, physical therapy to strengthen their body and chest therapy to help with recovery from the surgery itself.
Preventing Lung Adenocarcinoma
If you’re looking to maintain good health, there are several things that you can do. First and foremost, it’s crucial to avoid smoking. Not only is this habit dangerous to your health, but it can also expose others to secondhand smoke, which is harmful. This is why tobacco control is so important, not only for current smokers but for everyone’s health in general.
Another vital aspect of well-being is worker safety. If your job exposes you to toxic mists or vapors, it’s crucial to use the right equipment to avoid breathing it in. This typically involves wearing specialized masks or respirators. By taking these steps, you’re much less likely to inhale harmful substances, thus protecting your health.