At any time during a person’s lung cancer journey — from diagnosis through treatment and beyond — they may develop complications. These are health conditions that may be caused directly by lung cancer itself or as a side effect of cancer treatment. Complications of lung cancer can affect your quality of life — and some may even be life-threatening.

Learn more about common complications of lung cancer and symptoms to watch for so you can better navigate this difficult journey.

1. Superior Vena Cava Syndrome

Up to 4 percent of people with lung cancer at some point develop superior vena cava syndrome. The superior vena cava is a large vein that carries blood to the heart from the upper body. Superior vena cava syndrome occurs when the blood flow in this vein is blocked or compressed. Causes of obstruction can include blood clots or infections — sometimes near an implanted medical device, such as a pacemaker. However, cancer is the most common cause.

In lung cancer, obstruction of blood flow could be due to the compression of a tumor or enlargement of the lymph nodes that sit in between the lungs. Research indicates this condition occurs more often in small cell lung cancers (SCLC) — which commonly develop in the central region of the lungs — than in other types of lung cancer.

The most common symptoms of superior vena cava syndrome are:

• Coughing
• Dyspnea (shortness of breath)
• Swelling of the arms, chest, face, and neck

2. Blood Clots

Studies show that 3 percent of people with lung cancer experience venous thromboembolism as a complication. In venous thromboembolism, blood clots block the blood flow in veins, depriving cells, tissues, and organs of oxygen and leading to damage or even death.

Individuals with cancer are at higher risk of experiencing blood clots. According to the American Cancer Society, tissue damage caused by cancers triggers the body to release blood clotting factors, making clots more likely to form. Additional risk factors include:

• Being 40 and over
• Sustaining an injury to a vein
• Undergoing chemotherapy
• Having a blood-clotting disorder
• Smoking
• Getting insufficient exercise

Deep vein thrombosis and pulmonary embolism are two serious types of blood clots.

Deep Vein Thrombosis

Deep vein thrombosis, or DVT, occurs when a blood clot forms in the legs, arms, or other deep veins.

Symptoms of DVT watch for in the limbs include:

• Discoloration
• Swelling
• Pain
• Tenderness

If a piece of blood clot becomes dislodged, it’s called an embolus, and it can travel to the lungs and cause pulmonary embolism.

Pulmonary Embolism

Pulmonary embolism most often occurs when a piece of blood clot dislodges from deep veins in the leg and travels to the lungs, causing an obstruction. Pulmonary embolism can be life-threatening if it goes untreated, leading to potential complications including cardiac arrest, hypertension (high blood pressure), and arrhythmia (irregular heartbeat).

Symptoms of pulmonary embolism include:

• Coughing up blood
• Blue, clammy, or pale skin tone
• Excess sweating
• Rapid pulse
• Sharp chest pain similar to a heart attack
• Sudden shortness of breath
• Feelings of anxiety

3. Pancoast Syndrome

Pancoast syndrome is a collection of symptoms related to Pancoast tumors. These are tumors that develop on top of the lungs, and their growth may apply pressure on nerve endings that affect the chest, shoulder, and arm.

Pancoast tumors make up less than 5 percent of lung cancers, but according to the National Institutes of Health, non-small cell lung cancer accounts for more than 95 percent of all the cases of Pancoast tumors.

Symptoms to look for include:

• Arm and neck pain
• Sharp shoulder pain
• Muscle weakness
• Upper arm swelling

Horner’s Syndrome

According to Cleveland Clinic, 50 percent of people with Pancoast tumors develop Horner’s syndrome. Horner’s syndrome is a neurological (nerve-related) condition that affects one eye and the corresponding side of the face. It can result from damage to or blockage of the sympathetic nerves, which connect the brain and face nerves.

Symptoms include:

• Facial flushing
• Lack of sweat
• Smaller pupil and drooping eyelid on one side

4. Malignant Pleural Effusion

Around 40 percent of people with lung cancer develop malignant pleural effusion, according to Cancer.Net. This condition causes the buildup of fluid and cancer cells in the pleura — the space between the chest wall and the lungs.

According to studies, cancer cells can stimulate the overproduction of pleural fluid and interfere with proper drainage. Pleural effusion could be due to inflammation, obstruction, or trauma. Treatments such as radiation, chemotherapy, or surgery could also contribute to this condition.

Symptoms may involve:

• Chest pain
• Chest tightness
• Dry cough
• Inability to lie flat
• Shortness of breath

5. Pneumonia

Pneumonia affects an estimated 50 percent to 70 percent of people with lung cancer. It’s an infection that leads to inflammation in the lung tissue and produces fluid or pus in the lungs' air sacs.

People with cancer have a higher risk of infection because they have a weaker immune system. This may be due to cancer itself or cancer treatments. According to the American Lung Association, additional risk factors that increase the chances of developing pneumonia include:

• Being over age 65
• Having a chronic illness
• Smoking or abusing drugs or alcohol
• Being exposed to environmental pollution or toxins

Lung cancer and pneumonia share similar symptoms, but pneumonia can have other symptoms as well, depending on its underlying cause. Additional noteworthy symptoms of pneumonia include:

• A new cough that won't go away
• Fever
• Chest pain
• Chills
• Confusion in older individuals
• Phlegm that is yellow, green, or bloody

6. Spinal Cord Compression

About 19 percent of people with lung cancer experience spinal cord compression. Spinal cord compression can develop when a lung tumor affects a vertebral body (main portion of a vertebrae) and causes it to collapse or the spinal cord to compress. It can affect any part of the spine, from the neck to the lower back.

Individuals experience neurological symptoms that may include:

• Difficulty walking
• Limb weakness
• Loss of bowel or bladder control
• Numbness in the toes, fingers, or buttocks

7. Electrolyte Imbalance

Electrolytes are minerals that play a crucial role in maintaining the balance of fluids in the body and ensuring the proper functioning of vital organs and systems. Very high or very low levels of electrolytes may cause severe health problems. Electrolyte imbalances in individuals with lung cancer may include hypercalcemia (high calcium levels) and hyponatremia (low sodium levels).

Hypercalcemia

Hypercalcemia is a high calcium level in the body. According to Cleveland Clinic, about 90 percent of cases of hypercalcemia are due to cancers and hyperparathyroidism (when the parathyroid gland is overactive). Research on lung cancer suggests calcium may enter the bloodstream after a tumor metastasizes to bone.

Symptoms of hypercalcemia often present during advanced cancer stages. People may not show any symptoms in mild cases of hypercalcemia. Potential symptoms are:

• Fatigue
• Loss of appetite
• Constipation
• Difficulty concentrating
• Mood changes

Hyponatremia

Hyponatremia occurs when the body has low sodium levels in the blood. It develops in between 20 percent and 44 percent of people with lung cancer, mainly SCLC. The exact mechanism behind the relationship has yet to be fully understood. Still, like many complications, it could be due to other diseases, treatments, or the cancer itself.

According to one study in Advances in Kidney Disease and Health, certain cancer medications may be associated with the syndrome of inappropriate antidiuretic hormone (SIADH). In SIADH, the kidneys retain water, resulting in low sodium levels, which can lead to symptoms including:

• Confusion
• Headaches
• Nausea
• Vomiting
• Muscle weakness

Reducing Your Risk for Complications

While you may not be able to prevent complications of lung cancer, you can reduce your risks with the following considerations.

Avoid Smoking

Smoking causes lung cancer and other health complications. The National Institutes of Health recommends that smoking cessation provides better health benefits and prognosis (outlook) for individuals diagnosed with lung cancer.

Exercise

Exercise such as walking helps blood circulate and makes deep vein thrombosis less likely to develop. It can also improve a person’s response to cancer treatments and reduce treatment-related fatigue.

Eat a Healthy Diet

Make sure to maintain a healthy diet that includes fruits and vegetables. Always talk to your health care provider before taking dietary supplements, vitamins, or minerals. If you’re concerned about electrolyte imbalances, ask your doctor whether blood tests may be warranted.

Stay Up to Date on Vaccinations

According to the Cleveland Clinic, vaccinations are the best approach to prevent pneumonia. You should avoid contact with those who have infectious diseases and wash your hands after using the bathroom.

Follow Your Treatment Plan

Continue your plan of care as directed by your doctor. If you have other infections or health conditions that could worsen lung cancer, make sure your doctor is aware. You should always tell your provider about any new or worsening symptoms immediately.

Talk With Others Who Understand

On MyLungCancerTeam — the social network for people with lung cancer and their loved ones — more than 10,000 members come together to ask questions, give advice, and share their stories with others who understand life with lung cancer.

Have you developed any complications of lung cancer? How have complications affected your lung cancer treatment and quality of life? Share your experience in the comments below, or start a conversation by posting on your Activities page.