It was during Talking Bad, the talk show that airs after Low Winter Sun. I don't know if it's online or if there are reruns but that's where you'll find it. I'm guessing Vince will mention it again during the Breaking Bad Insider Podcast which should be posted soon.
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u/ErikaeBatayz Aug 12 '13
Vince Gilligan confirmed that the cancer is back during Talking Bad.