Mike

I've seen a few studies that cross referenced the Surveillance, Epidemiology, and End Results (SEER) program numbers but all they showed was that if you had oral cancer once, it could come back. Not exactly news. Since many people continue to smoke after cancer (amazing huh?) they can develop lung cancer.
Plus sometimes oral cancer metasizes and spreads to the lungs
So any numbers you find would just be SWAGs IMO.

Having had radiation twice, and over the "maximum", I had similar concerns but my RO said that its a theory that so far has not been substantiated.

As far as prostate cancer goes, every man who lives long enough will get it, but the vast majority die of something else.

While radiation is indeed the gift that keeps on giving, by itself oral cancer radiation TX has not been proven to cause other cancers in any credible study although of course the woo woo sites on the internet are full of such claims.