Not necessarily. 'speaking of which' would relate to the current subject/person under discussion. 'by the way' might be uttered to introduce a topic which has no revelance to the current topic under discussion but something said during that discussion reminded the person of something else.
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01cite10Gtivan12cite10It seems to me ,that they mean the same thing. 12br10 0-
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10Am I right or not ? 12br
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10Thanks, for your help12blockquote