Lumpectomy and radiation last year. Was small amt of cancer in node. Now small shadow on upper right lung CT but radiation on left side. Lung cancer?

Difficult to say. small shadow can be many different things. In the absence of old studies this could have been there for years. Old study is crucial before jumping to conclusions. Old granulomas from old infections can present the same way. It is best to err on the side of caution and have a follow up study to see if it changes before jumping to conclusions.