Kidney cancer is among the more common cancers affecting the urinary system, and it can sometimes extend beyond the kidneys. The lungs are the most frequent site for this spread, a process known as metastasis. Understandably, this possibility raises concerns for many people. 

Knowing how often this happens, why the lungs are particularly vulnerable, and how it’s managed can provide clarity and reassurance.

How does kidney cancer spread?

When cancer cells grow inside the kidney, some of them may break away and travel through the bloodstream or lymphatic system. These cells can then lodge in other organs and begin forming secondary tumours.

The lungs are especially at risk because blood from the kidneys returns to the body’s central circulation and passes directly through the lungs. They act as a natural filter, which means stray cancer cells often end up there.

It’s worth pointing out that not every kidney cancer spreads. Many cases are diagnosed at an early stage, when the tumour remains confined to the kidney. Detecting the cancer early improves the likelihood of curative treatment and reduces the risk of spread.

How often does kidney cancer spread to the lungs?

Research shows that 20–40% of people with kidney cancer eventually develop metastases, and the lungs are involved in the majority of these cases. More than half of all metastatic kidney cancers affect the lungs.

However, the likelihood depends on the stage at diagnosis. Around two-thirds of kidney cancers are identified while still localised, and for these patients, the risk of lung spread is relatively low. 

In contrast, when the disease is already advanced at the time of diagnosis, the chance of lung involvement is much higher.

Why are the lungs most affected?

The lungs’ role as a filter for blood is the main reason they’re commonly affected by kidney cancer. Every drop of blood returning from the body passes through the lungs to be oxygenated. As a result, any stray cancer cells travelling in the blood are likely to pass through the lungs first.

If these cells lodge in lung tissue, they may start to grow. Sometimes this results in a single nodule, while in other cases multiple spots appear across the lungs. These can be detected during follow-up scans, even if no symptoms are present.

It’s important to note that while the lungs are the most common site, they’re not the only one. Kidney cancer can also spread to bones, the liver, and the brain. Still, the lungs remain the primary site of spread due to circulation patterns.

Signs that kidney cancer has spread to the lungs

Lung metastases don’t always cause symptoms at first. In fact, many are discovered during routine scans after surgery or treatment for kidney cancer. When symptoms do appear, they may include:

• A persistent or worsening cough
• Shortness of breath that develops gradually
• Chest pain or tightness
• Coughing up blood, though this is less common

These symptoms can understandably cause worry. However, they’re not always due to cancer. Infections, asthma, or chronic lung disease can cause similar signs. That’s why any new or unexplained breathing problems should always be assessed by a doctor.

Diagnostic tests for lung spread

When kidney cancer patients are monitored, doctors usually arrange imaging tests at regular intervals. If there’s concern about possible spread to the lungs, tests may include:

• Chest X-rays, which provide a quick overview but are less detailed.
• CT scans, which are more precise and can reveal nodules too small to be picked up on an X-ray.
• MRI scans, which are occasionally used when a clearer view is needed.

In certain cases, doctors may recommend a biopsy to confirm whether a lung nodule is related to kidney cancer or another condition. The type of scan and frequency of monitoring depend on individual risk factors, such as the original tumour’s size and grade.

Treatment options when kidney cancer spreads to the lungs

Treatment is tailored to each patient’s circumstances. Factors such as the number and size of lung metastases, their location, and overall health all play a part in deciding the best approach. Options may include:

• Targeted therapy: These medicines block specific pathways that cancer cells rely on to grow and spread.
• Immunotherapy: These treatments encourage the immune system to recognise and attack cancer cells. Drugs like checkpoint inhibitors have improved survival for many patients with advanced kidney cancer.
• Surgery: If there are only a few lung metastases and the cancer is otherwise controlled, surgery to remove them may be an option. This is known as pulmonary metastasectomy.
• Radiotherapy: Sometimes used to relieve symptoms or treat a limited number of metastases.

Your healthcare team will weigh the benefits and risks of each treatment, always keeping your quality of life in mind.

Factors that influence the likelihood of lung spread

Several factors can raise or lower the risk of kidney cancer spreading to the lungs:

• Stage of cancer at diagnosis: Localised cancers have a much lower chance of spreading than those already advanced.
• Tumour grade: Higher-grade tumours are more aggressive and more likely to spread.
• Type of kidney cancer: Clear cell renal cell carcinoma is the most common subtype and carries its own patterns of spread.
• General health: A patient’s immune system and overall health may influence the body’s ability to resist spread.

Final notes

Around one in four to one in three patients with advanced disease experience lung involvement, making it the most common site of spread. Still, not everyone with kidney cancer will face this outcome, especially when the cancer is found and treated early.

Read more: What Are The Chances Of Kidney Cancer Spreading?