Kidney cancer, also known as renal cell carcinoma (RCC), can spread to other parts of the body. The lungs are a common site for this spread, which is referred to as metastasis.
How Kidney Cancer Spreads to the Lungs
Kidney cancer cells can detach from the primary tumor and travel to distant sites within the body. The most common pathway for kidney cancer to spread is through the bloodstream, a process known as hematogenous spread. Cancer cells enter small blood vessels within or near the kidney, circulate through the body, and then lodge in the capillaries of other organs. The lymphatic system can also serve as a route for cancer cell dissemination, though this is less common for initial lung metastasis compared to blood vessels.
The lungs are a frequent destination for metastatic kidney cancer due to their extensive capillary network, which provides an ideal environment for circulating cancer cells to become trapped and establish new tumors. Once settled, these cells begin to divide and form metastases within the lung tissue. Approximately 25% to 30% of individuals with kidney cancer have distant metastases at their initial diagnosis, with the lungs being the most common site.
Identifying Lung Metastasis
When kidney cancer spreads to the lungs, it can cause various symptoms. Individuals might experience a persistent cough, shortness of breath, or chest pain. Some may also cough up blood, indicating irritation or damage to the lung tissues. These symptoms arise as the growing tumors interfere with normal lung function, potentially blocking airways or increasing pressure.
Lung metastases are not always symptomatic and may be discovered incidentally during routine medical imaging. Doctors utilize several diagnostic tools to detect and confirm lung metastasis. Chest X-rays can reveal abnormalities, but more detailed imaging like computed tomography (CT) scans of the chest are often used to identify smaller nodules or masses. Positron emission tomography (PET) scans can also help locate metastatic lesions by detecting areas of increased metabolic activity. A biopsy of the suspicious lung tissue is typically performed to provide a definitive diagnosis, confirming the presence of kidney cancer cells.
Treatment and Prognosis for Lung Metastasis
Treating kidney cancer that has spread to the lungs involves various approaches, tailored to the individual patient. Treatment decisions consider factors such as the number and size of the lung metastases, the patient’s overall health, and any prior treatments. Systemic therapies, which treat cancer throughout the body, include targeted therapies and immunotherapy. Targeted therapies work by interfering with specific molecules involved in cancer cell growth and blood vessel formation, while immunotherapies stimulate the body’s own immune system to recognize and attack cancer cells.
Local treatments, such as radiation therapy or surgical removal of the metastases (metastasectomy), may also be considered. Radiation therapy, particularly stereotactic body radiation therapy (SBRT), can precisely target and destroy lung tumors, offering local control and symptom relief. Surgical removal of lung metastases can be an option for carefully selected patients, especially those with a limited number of resectable tumors and no other widespread disease. Pulmonary metastasectomy can lead to 5-year survival rates ranging from 21% to 60% in selected cases, particularly with complete removal of the tumors.
The prognosis for metastatic kidney cancer to the lungs has improved with advancements in treatment. While a cure for metastatic kidney cancer is challenging, current therapies aim to control disease progression, manage symptoms, and enhance quality of life. The 5-year survival rate for stage 4 kidney cancer that has spread to distant sites, including the lungs, is approximately 18%. Individual outcomes can vary widely depending on specific disease characteristics and response to treatment.