Synchronous primary lung cancers.

Synchronous primary lung cancers (SPLCs) occur in up to 0.5% of patients with lung cancer. They are first diagnosed intraoperatively or upon pathologic examination of resected tissue in up to 40% of patients with SPLCs. Complete surgical resection is possible in over 90% of patients, with an operative mortality of 2.1%. Despite a high frequency of early stage disease (two thirds of patients have either stage I or II tumors), surgical therapy yields an overall 5-year survival of only 20%, far lower than expected. These findings suggest that the biology of SPLCs is different from that of ordinary lung cancers, or that the diagnosis of SPLCs is being made too often, and that in some patients the second cancer focus actually represents metastatic disease. The use of newer techniques of identifying the molecular and biologic characteristics of these cancers, including analysis of DNA ploidy patterns, may more accurately define SPLC patients. Optimal interventional and preventive therapies remain to be determined.