Michelle,
From your signature I gather that Dan just recently finished IMRT.
Metabolically active means that it accumulated glucose.... but that does not mean it is cancer. There are many reasons why there is an uptake:
Exercise, inflammation, scar tissue etc. This especially since he just finished rads. Enlarged nodes and some activity especially this close to the treatment is not all that unusual.
Before you go nuts consider the above and call the MO (why not RO?) on Monday to get their take on this.

Markus

Markus