His diabetes is in remission. We're to keep feeding him the diabetic food (DM), alternating with the Purina E/N that's good for Aoki (and which both cats devour like whoa), but now we can reward them occasionally with some nice wet food (they particularly like salmon). The DM is also preventative, so it's good that he keeps eating it (and good for Aoki, too).
Marcus has now officially beaten cancer (back in '04) and diabetes. And he's still going strong at 17.