Cancers often spread, or metastasize, from the primary tumor to nearby structures, including the lungs. Lung metastasis occurs in the pulmonary parenchyma and can be a significant cause of morbidity and mortality from cancer. Metastases from several types of tumors can metastasize to the lungs and may be found on imaging studies, such as a CT scan or MRI. The underlying genetic and pathologic processes that lead to the formation of metastases from primary cancers are complex. A combination of molecular and immunohistochemical techniques are used to identify the origin of lung metastases.
Metastases that originate from different organs can spread to the lungs through various pathways, including hematogenous or lymphatic spread. Hematogenous spread is more common and occurs when cancer cells leak from primary tumors into small blood vessels that lead to the lungs. This type of spreading is more common in tumors that drain into the lungs via the venous system, such as colorectal cancer, head and neck cancer, melanoma, and soft tissue and bone sarcoma. Lymphatic spread is also more common and involves the spread of cancer through the vascular space (the space that surrounds and protects the lungs) or into the airways of the lungs. This type of spreading is seen more commonly in tumors that drain into the lungs through the lymphatic system, such as melanoma, sarcoma, and osteosarcoma.
Once cancer cells have metastasized to the lungs, they can be recognized on CT scans or MRIs, as well as on biopsy. In some cases, lung metastases are present in patients with no symptoms and may only be discovered when the patient undergoes a routine diagnostic test or exam for another condition. In other cases, lung metastases can cause general symptoms such as fatigue or unexplained weight loss. Once the presence of lung metastases is confirmed, treatment can begin.
If the primary cancer from which the metastases originated is not diagnosed or treated, prognosis can be very poor. However, it is important to note that the 5-year survival rate for hematogenous metastasis to the lungs varies depending on the specific tumor type. For example, patients with hematogenous metastases to the kidney, adrenal glands, or central nervous system have much lower survival rates than those who do not have these locations as a site of metastases.
In the past, healthcare providers had limited options for treating a cancer that had spread to the lungs. However, new treatments are now available to help patients with metastatic disease extend their lives and improve quality of life. At Froedtert & the Medical College of Wisconsin, we use an interprofessional team approach to treat cancers that have spread to the lungs. This allows us to take advantage of the expertise of many different specialists and offer our patients the best possible care. Newer treatments include radiofrequency ablation and stereotactic radiation, which can be delivered through a minimally invasive procedure using a thin tube that is guided by computer images. Our research team is investigating new treatments, such as cellular immunotherapy and genomic therapy, that can potentially benefit patients with this challenging stage of cancer.
