carol,
my sister's recurrence (near the site of the first tumour, on the other side of her neck) was discovered as she was finishing her radiation, in fact, about a week before the end of treatment. as i understand it, the protocol is to give radiation to both sides precisely because of the high rate of recurrence in SCC cases, often in close neighbouring areas. if they're not giving her radiation on both sides, perhaps you should ask them to explain why.
be well.
gita