Kidney cancer, medically known as renal cell carcinoma (RCC), originates in the kidneys. Like many cancers, RCC has the capacity to spread from its initial site to other parts of the body, a process called metastasis. This occurs when cancer cells break away from the primary tumor and travel through the bloodstream or lymphatic system to form new tumors elsewhere.
How Often Kidney Cancer Spreads to the Lungs
The lungs are a common site for kidney cancer to spread. Over 50% of patients with metastatic renal cell carcinoma experience lung metastasis, with some reports indicating this accounts for 45-80% of cases. This prevalence is due to the lungs’ rich blood supply and their role as filters for blood circulating throughout the body, making them accessible to circulating cancer cells.
Approximately one-third of individuals diagnosed with renal cell carcinoma already have metastatic disease at the time of diagnosis. For those initially diagnosed with localized kidney cancer, about 20-30% may develop metastatic spread during follow-up, with the lungs being a common site for these recurrences. The median time for recurrence in the lungs is typically 15-18 months after initial kidney surgery, with a majority occurring within three years.
Factors Influencing Metastasis
Several factors influence the likelihood of kidney cancer spreading, including its stage, grade, and specific subtype. The stage of cancer at diagnosis, which describes its size and how far it has spread, is a primary determinant of metastatic potential. Larger primary tumors show a higher probability of metastasis, with rates ranging from 3.6% for tumors 4 cm or smaller to 45.1% for tumors larger than 10 cm.
The aggressiveness, or grade, of the tumor also plays a role. Higher-grade tumors, where cancer cells appear less like normal kidney cells under a microscope, tend to grow more quickly and are more likely to spread.
Specific subtypes of renal cell carcinoma also exhibit varying metastatic tendencies. Clear cell renal cell carcinoma (ccRCC), the most common type, is frequently associated with lung metastasis and accounts for roughly 80% of metastatic RCC cases. Conversely, chromophobe RCC (chRCC) has lower metastatic rates even at larger tumor sizes, while sarcomatoid RCC (sarcRCC) shows high metastatic rates across all tumor sizes.
Detecting Lung Metastasis
Detecting lung metastasis from kidney cancer often involves observing patient symptoms and utilizing diagnostic imaging. Patients might experience symptoms such as a persistent cough, shortness of breath, or chest pain or discomfort. These symptoms can arise because the metastatic tumors in the lungs can block airways or affect lung function.
Imaging techniques like chest X-rays, computed tomography (CT) scans, and PET scans are used to identify lung metastases and provide detailed information about the extent of cancer spread. In some cases, a biopsy of the lung lesion may be performed to confirm the presence of kidney cancer cells. Regular monitoring with imaging is part of the follow-up care for individuals diagnosed with kidney cancer to detect any potential spread early.
Implications and Management of Lung Metastasis
When kidney cancer spreads to the lungs, it indicates advanced disease, often referred to as stage IV. While a cure may not be possible at this stage, treatment approaches aim to control the cancer, manage symptoms, and improve quality of life. Management is individualized, considering the patient’s overall health, the extent of metastasis, and the specific characteristics of the tumor.
Systemic therapies, which target cancer cells throughout the body, are employed. These include targeted therapy drugs that interfere with specific pathways cancer cells use to grow, and immunotherapy, which harnesses the body’s own immune system to fight cancer.
Local treatments may also be considered, particularly if there are only a few metastatic lesions in the lungs. Surgical removal of lung metastases (pulmonary metastasectomy) can be an option for select patients, potentially slowing disease progression. Radiation therapy, including stereotactic body radiotherapy (SBRT), can also be used to target and shrink tumors in the lungs, helping to alleviate symptoms like breathlessness.