Does bad smelling flatulence mean cancer?

This is unlikely: Nothing is impossible, but the inability to digest fat can lead to this. The hardest part of your question is defining bad smelling flatulence: many feel it all smells bad. Sometimes getting ones gut flora back to a normal state can help: yogurt and probiotics. But if you are worried, see your doctor for physical. It is not impossible if one cannot digest fat due to cancer to have this sign.