Metastatic cancer to the lungs (secondary lung cancer) is cancer that has spread to the lungs from another part of the body. This is common because many cancers spread to this organ.

According to the National Cancer Institute, the most common cancers that spread to the lungs are breast, bladder, colon, rectum, kidney, ovarian, uterine, pancreatic, prostate, thyroid, and melanoma. Lung metastases also occur frequently in sarcomas, a rare type of cancer that begins in bone or muscle tissue. About 20% of soft tissue sarcomas and 40% of bone sarcomas spread to the lungs.

When a tumor begins to metastasize in the esophagus or chest wall, it can spread directly to the lungs. But most cancer cells travel to the lungs indirectly through three routes. Cancer cells enter small blood vessels near the tumor and are carried to the lungs through the pulmonary arteries, a process called hematogenous spread. Lymphatic spread occurs when tumor cells enter small lymph vessels and travel along the lymphatic system, including the lymph nodes. Spread to the pleura and airways is limited to lung tumors and is less common.

Lung metastases often do not cause symptoms. In some cases, lung metastases cause symptoms similar to those of primary lung cancer (a tumor that begins in the lung). These include a persistent cough; coughing up blood; chest, shoulder, and back pain; shortness of breath; low blood oxygen levels; and fluid in the pleural space. Fatigue, unexplained weight loss, and loss of appetite are also common in people with metastatic cancer.

Chest X-ray, PET, chest CT, lung biopsy, pleural fluid analysis, bronchoscopy are used to diagnose lung metastasis. Treatment may include chemotherapy, surgery, hormonal therapy, targeted therapy, immunotherapy or a combination of these.

Chemotherapy is often used as palliative therapy to prolong life and relieve symptoms. Metastatic cancer is usually incurable. In rare cases, chemotherapy can cure testicular cancer that has spread to the lungs.

Inhaled chemotherapy is being studied to deliver the drugs directly to the lungs, which may be more effective and have fewer side effects. Complete surgical removal of the primary tumor and all metastases may improve survival.

According to the American Society of Clinical Oncology, the five-year survival rate after a diagnosis of lung metastases depends on the primary tumor. For example, the five-year survival rate for testicular cancer that has spread to the lung is 74 percent, for breast cancer that has spread to the lung is 28 percent, and for ovarian cancer that has spread to the lung is nearly 15 percent.

Mai Cat (According to Very Well Health )