Lung cancer ranks among the most common and most lethal malignancies worldwide. In 2006, approximately 174,470 of an estimated 1,399,790 (12%) new cancer cases, and 162,460 of an estimated 564,830 (28%) total cancer deaths, in the United States were attributable to lung cancer. Similarly, in the 38 countries in Europe, lung cancer accounted for 12 percent of approximately 3.2 million new cancer cases and 19.7 percent of cancer-related deaths. Lung cancer is classified into two major groups: non–small-cell lung cancer (NSCLC), which accounts for 75 percent of all cases, and small-cell lung cancer (SCLC), which accounts for approximately 25 percent. NSCLC is further divided into three histologic subtypes: adenocarcinoma (30%–40%), squamous cell carcinoma (SCC; 20%–25%), and large cell carcinoma (15%–20%). Approximately half of patients with NSCLC already have metastatic (stage IV) disease at the time of diagnosis, and survival times are short regardless of the type of chemotherapy administered.
Several platinum-based chemotherapy regimens are available; they generally yield similar outcomes, with median time to progression of four months and median survival of eight months. Compared with other common primary tumors, such as colorectal and breast cancer, where the median survival is more than twenty months, the prognosis of metastatic NSCLC remains extremely poor. Similar to breast cancer, bone and lung metastases are particularly frequent in NSCLC. However, the different distribution patterns of metastases in lung carcinoma are poorly understood, probably because studies are difficult, given the extremely short survival times and high proportion of patients who have widespread metastases at the time of diagnosis.