Lung cancer is the second most common type of cancer in the United States. Almost half of people with advanced lung cancer develop pulmonary arterial hypertension (PAH), a type of high blood pressure in the lungs called pulmonary hypertension (PH). This condition makes it harder for blood to flow.

Think of your lungs like a highway system, with blood vessels acting as roads that keep oxygen moving. When lung cancer is in the mix, it’s like a traffic jam forming — narrowing lanes and slowing circulation. Over time, PH forces the heart to work harder to push blood through, putting extra strain on the body.

If you or a loved one has been diagnosed with lung cancer, it’s important to know about this possible roadblock. Keep reading to learn more about how lung cancer can lead to PH and what that means for your health.

Lung Cancer-Related Conditions That Cause PH

Lung cancer can cause complications that may lead to PH. These problems affect the blood vessels and make it harder for blood to move through the lungs. Inflammation and tumors can damage the arteries, while blood clots can create blockages that raise pressure. Over time, these changes put extra strain on the heart and make it harder to breathe.

Blood Vessel Inflammation

PAH (also known as group 1 PH) is caused by damage to the blood vessels in the lungs. Blood vessel damage can occur in lung cancer due to inflammation. In lung cancer, the immune system uses inflammation to help fight the cancer. However, the immune cells can cause harmful inflammation in the lungs’ blood vessels.

A 2017 study found that about half of people with lung cancer had thickening in the blood vessels of the lungs, a sign of PAH. PAH in lung cancer may be linked to worsening lung cancer symptoms, such as dyspnea (shortness of breath).

Tumors That Block Blood Vessels

Group 4 PH can develop if a lung tumor presses on the pulmonary artery (the blood vessel that carries blood from the heart to the lungs). A large lung tumor can disrupt the normal flow of blood through the lungs. The disrupted blood flow puts more strain on the right side of the heart and raises the pulmonary artery pressure.

Tumor cells can also block blood vessels. Cancer may lead to pulmonary tumor embolism (PTE) or pulmonary tumor thrombotic microangiopathy (PTTM). In these conditions, tumor cells in one part of the body move into nearby blood vessels and travel throughout the bloodstream to other locations. They then become lodged in the blood vessels of the lungs, forming clumps that prevent blood from flowing normally.

As many as 1 in 4 people with any type of cancer may have PTE, although many don’t have symptoms and are never diagnosed with the condition. PTTM is rarer and more serious than PTE. Both conditions tend to occur alongside adenocarcinoma, a type of lung cancer that starts in the cells lining the lungs and makes mucus.

Blood Clotting Problems

People with all types of cancer have an increased risk of developing blood clots. This can happen if tumor cells release substances that encourage the blood to clot. People with lung cancer have one of the highest risks of developing venous thromboembolism. The risk of blood clots is highest in people with advanced cancer and those treated with chemotherapy drugs.

A blood clot can prevent blood from flowing through veins and arteries. When a person develops serious blood clots, it’s known as venous thromboembolism (VTE). VTEs that occur in the blood vessels of the lungs are called pulmonary embolisms.

Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare type of PH that develops when blood clots form in the blood vessels of the lungs and fail to dissolve. CTEPH causes scar tissue to build up, which may eventually block the blood vessels completely. People with any type of cancer are 3.76 times more likely to develop CTEPH.

PH as a Side Effect of Lung Cancer Treatment

Some cancer treatments can increase your risk of developing high blood pressure in the arteries of the lungs. That’s because some lung cancer treatments cause cardiovascular (heart) and pulmonary (lung) toxicity.

Radiation Therapy

Radiation is a treatment option for people with lung cancer. During radiation therapy, radioactive beams or particles are delivered to a tumor. This treatment often works well to destroy cancer cells, but may also damage the surrounding healthy tissue. When used to treat lung cancer, radiation therapy is aimed at the chest and lungs.

PH is relatively common in people who have had radiation therapy for lung cancer. A 2024 study found that between 13 percent and 25 percent of people with lung cancer treated with radiation had pulmonary hypertension within two years of treatment.

There are several ways radiation therapy may lead to PH. In some cases, radiation treatments damage blood vessels. This can lead to a condition called pulmonary veno-occlusive disease (PVOD), in which small veins in the lungs become blocked. PVOD is a type of group 1 PAH. People who have undergone radiation treatments sometimes develop PVOD several years later.

Radiation therapy may also lead to heart problems, which could cause group 2 PH. Additionally, people who receive multiple radiation treatments to the chest can develop lung tissue damage, which sometimes leads to group 3 PH.

Chemotherapy

Chemotherapy (chemo) is a common treatment option for people with lung cancer. Chemo may be used to shrink a tumor before or after surgery or as a main treatment instead of surgery.

Chemo drugs often travel within blood vessels throughout the body. They may harm the blood vessels, leading to PVOD. Chemotherapy-related PVOD may be more common in a group of chemotherapy drugs called alkylating agents. Cisplatin (Platinol), mitomycin (Mutamycin) and ifosfamide (Ifex) are examples of alkylating agents that may be used to treat lung cancer.

Chemotherapy drugs may also damage the heart or lungs, leading to heart failure or lung conditions, which can lead to group 2 or group 3 PH.

Targeted Therapy Drugs

Targeted therapy drugs are a type of lung cancer therapy that works differently to stop the growth of cancer cells. Tyrosine kinase inhibitors (TKIs) are a type of targeted therapy that can increase the risk of developing group 1 PAH. TKIs, like lorlatinib (Lorbena), may cause PAH by directly damaging the blood vessels in the lungs. Additionally, some TKIs can cause heart problems that lead to PH. In many cases, PH will get better once the TKI drug is stopped. However, TKIs have caused permanent lung damage requiring a lung transplant.

Immunotherapy

Immunotherapy treatments for lung cancer use your own immune system to help fight cancer. Immune checkpoint inhibitors are a type of immunotherapy that have been associated with PH. These drugs may cause PH by damaging the heart, increasing the risk of VTE, and causing lung inflammation.

Nivolumab (Opdivo) and atezolizumab (Tecentriq) are immune checkpoint inhibitors associated with a risk of developing PH.

Other Risk Factors for PH

In some cases, PH and cancer may not be directly related to each other. Instead, they may be comorbidities — health conditions that occur at the same time. Certain risk factors may increase a person’s chances of developing both PH and lung cancer. Alternatively, a person may be at risk for both conditions due to independent factors.

Shared Risk Factors

One risk factor that PH and cancer have in common is older age. PH can occur at any age, but it is more common in older adults. Most people with lung cancer are over the age of 65. Other risk factors that can increase the risk of PH and lung cancer include:

• Exposure to asbestos (a type of mineral made up of many small fibers, found in soil and certain consumer products)
• Exposure to tobacco smoke
• Previous radiation therapy

Independent Risk Factors

Some people may have risk factors that predispose them to develop PH and separate risk factors that could lead to lung cancer.

Several other PH risk factors can occur separately from cancer. These include:

• Having health conditions that lead to blood clotting
• Having lung disorders such as chronic obstructive pulmonary disease
• Having kidney disease
• Congenital heart disease (a condition present at birth that affects the way the heart works)
• Using certain illegal drugs
• Being HIV positive
• Taking the weight loss drug fen-phen
• Having obstructive sleep apnea
• Living at a high altitude

Likewise, some cancer risk factors don’t have any known connection to PH. Lung cancer is more likely to develop in some people. Risk factors for lung cancer include:

• Having been exposed to radon (radioactive gas)
• Drinking water with high levels of arsenic
• Smoking while taking a beta-carotene supplement
• Being exposed to certain workplace chemicals
• Having a personal or family history of lung cancer

How Does PH Impact Lung Cancer Outlook?

People who develop PH with lung cancer may have worse outcomes than other people with lung cancer. If you have lung cancer, your healthcare team will monitor you closely for signs and symptoms of PH. It’s important to notify your healthcare provider right away if you notice any new symptoms, like shortness of breath. Early detection of PH may help improve your outcomes.

Talk With Others Who Understand

On myPHteam, the social network for people with pulmonary hypertension, more than 56,000 members come together to ask questions, give advice, and share their stories with others who understand life with pulmonary hypertension.

Do you have a history of lung cancer? Share your experience in the comments below, or start a conversation by posting on your Activities page.