Occurrence and prognosis of lung cancer metastasis to major organs: a population-based study

Background Lung cancer metastasis to major organs is an important factor affecting survival. We analyzed the influence of patient characteristics on the incidence and survival of metastasis to major organs. Methods We collected data from the Surveillance, Epidemiology, and End Results database on 58 659 patients diagnosed with stage IV primary lung cancer, including age, sex, race, histological type of tumor, laterality, primary site, number of extrametastatic sites, and treatment. Results Multiple variables affected the incidence of metastasis to major organs and survival. According to histological type of tumor, the following were more common: bone metastasis from adenocarcinoma; brain metastasis from large-cell carcinoma and adenocarcinoma; liver metastasis from small-cell carcinoma; and intrapulmonary metastasis from squamous-cell carcinoma. A larger number of metastatic sites increased the risk of other metastases and shorter survival. Liver metastasis conferred the worst prognosis, followed by bone metastasis, and brain or intrapulmonary metastasis conferred better prognosis. The effect of radiotherapy alone was poorer than chemotherapy alone or combined chemotherapy and radiotherapy. In most cases, the effects of chemotherapy and combined chemotherapy and radiotherapy were equivalent. Conclusion Multiple variables affected the incidence of metastasis to major organs and survival. Compared with radiotherapy alone or combined chemotherapy and radiotherapy, chemotherapy alone may be the most cost-effective option for patients with stage IV lung cancer.