Thanks for this Brian - so am I right in understanding that mets would be cancer spread through the lymphs or blood system where as a second primary would be caused by what ever caused the original cancer, but just be in a different location?

Is it easy for medics to assess the difference in the case of lung tumours identified on scans? The reason why I ask is that the few journal articles I have located on distant mets suggest that the mean time to spread is about 4 years and I just wonder whether that is accurate or whether their figures include second primaries? Also found some quite old articles claiming reasonable survival rates for resection of lung mets, which I found odd as resection very rarely seems a clinical option for mets?